Electroactive ionic liquids and surface-modified substrates containing them

Abstract

The present invention relates an electro-active polymeric ionic liquid including imidazolium-based molecules, said imidazolium-based molecule comprising each at least: one imidazolium moiety associated with a negatively-charged counter-ion, and one reducible group selected from: Formula (IV), an anthraquinone derivative of formula (IV): with R.sub.1 representing a hydrogen atom or a C.sub.1-C.sub.6-alkyl group, a viologen group, and a metallocene reducible group such as a cobaltocene group.

Claims

1. An electro-active polymeric ionic liquid comprising imidazolium-based repeated units, each of said imidazolium-based repeated units comprising at least: an imidazolium moiety associated with a negatively charged counter-ion, a metallocene oxidizable group and/or a reducible group, the reducible group being selected from: an anthraquinone derivative of formula (IV): ##STR00084## with R.sub.1 representing a hydrogen atom or a C.sub.1-C.sub.6-alkyl group, a viologen group of formula (V): ##STR00085## with R.sub.2 representing a hydrogen atom, a C.sub.1-C.sub.8 alkyl group or a C.sub.2-C.sub.6 alkenyl group, X and X identical or different, and each independently representing a halogen group, or a metallocene reducible group.

2. The electro-active polymeric ionic liquid according to claim 1, wherein the polymeric ionic liquid presents: imidazolium-based repeated units, each of said imidazolium-based repeated units comprising at least: an imidazolium moiety associated with a negatively charged counter-ion, and a metallocene oxidizable group and imidazolium-based repeated units, each of said imidazolium-based repeated units comprising at least: an imidazolium moiety associated with a negatively charged counter-ion, and a reducible group, the reducible group being selected from an anthraquinone derivative, a viologen group, or a metallocene reducible group.

3. The electro-active polymeric ionic liquid according to claim 1, wherein the imidazolium-based repeated units comprise: an imidazolium moiety associated with a negatively charged counter ion, and a metallocene oxidizable group, and a reducible group selected from anthraquinone derivative, a viologen group, or a metallocene reducible group.

4. Electro-active polymeric ionic liquid of claim 1, wherein the polymeric ionic liquid is polymerized from an imidazolium-based molecule of formula (I): ##STR00086## wherein m is 0 or 1; n is equal to 0 or 1; L.sub.1 is selected from: a bond, a C.sub.1-C.sub.6 alkyl group where one or two carbon atoms are optionally replaced by an oxygen atom, a CO(C1-C6)alkyl group, a (C1-C6)alkyl-CO group, a CONH(C.sub.1-C.sub.6)alkyl group, a (C.sub.1-C.sub.6)alkyl-CONH group, a COO(C.sub.1-C.sub.6)alkyl group, and a (C.sub.1-C.sub.6)alkyl-COO group; A and B are different and are selected from: an imidazolium group of formula (IIa): ##STR00087## Z.sup. being a negatively charged counter ion, a metallocene oxidizable group of formula (III) ##STR00088## M being a transition metal ion, or a reducible group selected from: an anthraquinone derivative of formula (IV): ##STR00089## with R.sub.1 representing a hydrogen atom or a C.sub.1-C.sub.6-alkyl group, or a metallocene reducible group, or a viologen group of formula (V): ##STR00090## with R2 representing a hydrogen atom, a C.sub.1-C.sub.8 alkyl group or a C.sub.2-C.sub.6 alkenyl group, and X and X identical or different, and each independently representing a halogen group, provided that at least A or B is an imidazolium group of formula (IIa), when n is 1, then C is selected from: a metallocene oxidizable group of formula (III) as defined above, or a reducible group as defined above, provided that A, B and C are different; L.sub.2 is selected from a bond, a C.sub.1-C.sub.6 alkyl group, a CONH(C.sub.1-C.sub.6)alkyl group, a (C.sub.1-C.sub.6)alkyl-CONH group, a COO(C.sub.1-C.sub.6)alkyl group, and a (C.sub.1-C.sub.6)alkyl-COO group, wherein one or two carbon atoms in the (C.sub.1-C.sub.6)-alkyl group are optionally replaced by an oxygen atom, a CO(C.sub.1-C.sub.6)alkyl group, a (C.sub.1-C.sub.6)alkyl-CO group, when n is 0, then A and B are different and are selected from an imidazolium group of formula (IIa) as defined above, and a reducible group as defined above L.sub.2 is a C.sub.1-C.sub.6 alkyl group if B is an imidazolium group of formula (IIa) when m is 1 then A or B is an imidazolium group of formula (IIa), A is not a viologen group of formula (V) as defined above, L.sub.3 is selected from a bond, a C.sub.1-C.sub.6 alkyl group, a CONH(C.sub.1-C.sub.6)alkyl group, a (C.sub.1-C.sub.6)alkyl-CONH group, a COO(C.sub.1-C.sub.6)alkyl group, and a (C.sub.1-C.sub.6)alkyl-COO group, wherein one or two carbon atoms in the (C.sub.1-C.sub.6)-alkyl group are optionally replaced by an oxygen atom, and R is a hydrogen atom, a C.sub.1-C.sub.6 alkyl group or a C.sub.5-C.sub.10-aryl group; when m is 0 then L.sub.3 is a hydrogen atom if A is metallocene oxidizable group of formula (III) or a reducible group, L.sub.3 is a C.sub.1-C.sub.6 alkyl group if A is an imidazolium group of formula (IIa), and one of A and C is a viologen group of formula (V) as defined above with R.sub.2 representing a C.sub.2-C.sub.6 alkenyl group.

5. The electro-active polymeric ionic liquid of claim 1, wherein the reducible group is an anthraquinone derivative of formula (IV) with R.sub.1 representing a hydrogen atom.

6. The electro-active polymeric ionic liquid of claim 1, wherein the metallocene oxidizable group is a ferrocene group.

7. The electro-active polymeric ionic liquid of claim 1, wherein the negatively charged counter-ion is PF.sub.6.sup., BF.sub.4.sup., Cl.sup., Br.sup. or bis(trifluoromethanesulfonyl)imidate CF.sub.3SO.sub.2NSO.sub.2CF.sub.3.sup..

8. The electro-active polymeric ionic liquid of claim 1, wherein said imidazolium-based molecule is selected from: ##STR00091## with Z.sup., Z.sub.1.sup., X.sup. and X.sup. as defined in claim 4.

9. The electro-active polymeric ionic liquid of claim 1, wherein said imidazolium-based molecule is: ##STR00092## with Z.sup. being a negatively charged counter ion, X.sup. and X.sup. being identical or different, and each independently representing a halogen group.

10. Surface-modified substrate with an immobilized electro-active polymeric ionic liquid as defined in claim 1.

11. The surface-modified substrate of claim 10, wherein the substrate is a current collector of an electrode.

12. The surface-modified substrate of claim 10, wherein on the substrate is immobilized: a combination of: 1) an electro-active polymeric ionic liquid comprising imidazolium-based repeated units comprising at least one imidazolium moiety, one negatively charged counter-ion and one metallocene oxidizable group, and 2) an electro-active polymeric ionic liquid comprising imidazolium-based repeated units comprising at least one imidazolium moiety, one negatively charged and one reducible group, or an electro-active polymeric ionic liquid comprising imidazolium-based repeated units comprising at least: 1) one imidazolium moiety associated with one negatively charged counter-ion, 2) one metallocene oxidizable group and 3) one reducible group.

13. An energy storage device comprising at least two surface-modified electrodes comprising a surface-modified substrate with an immobilized electro-active polymeric ionic liquid as defined in claim 1, wherein the substrate is a current collector of an electrode, and wherein the two surface-modified electrodes are different, and the first electrode comprises a electro-active polymeric ionic liquid with imidazolium-based repeated units comprising at least: one imidazolium moiety associated with one negatively charged counter-ion, and one metallocene oxidizable group; and the second electrode comprises an electro-active polymeric ionic liquid with imidazolium-based repeated units comprising at least: one imidazolium moiety associated with one negatively charged counter-ion, and one reducible group as defined in claim 1.

14. An energy storage device comprising at least two surface-modified electrodes comprising a surface-modified substrate with an immobilized electro-active polymeric ionic liquid as defined in claim 1, wherein the substrate is a current collector of an electrode, and wherein the two surface-modified electrodes are identical, and the first and second electrode comprise a electro-active polymeric ionic liquid with imidazolium-based repeated units comprising at least: one imidazolium moiety associated with one negatively charged counter-ion, one metallocene oxidizable group, and one reducible group as defined in claim 1.

15. The energy storage device according to claim 14, wherein the surface of the surface-modified electrode is as follows: ##STR00093## ##STR00094##

16. The energy storage device according to claim 15, wherein the surface-modified electrodes are planar, interdigitated and membraneless.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, CV stands for Cyclic voltammetry, and GC stands for glassy carbon, Fc stands for ferrocene and AQ stands for anthraquinone.

(2) FIG. 1. XPS high resolution spectra for C(1s), N(1s), Fe(2p) and F(1s) of poly(FcIL) deposited on ITO surface in example 1. Inset XPS survey scan.

(3) FIG. 2. (a) AFM topography image of Au modified with the initiator layer (b) SEM image of the poly(FcIL) growth on Au. Scale bare 1 m (c) AFM topography and 3D AFM image representation of poly(FcIL) onto Au substrate, image size 44 m.sup.2. (d) AFM topography and 3D AFM image representation performed in the same area as (c) using scan angle of 45. (e) Cross section after scratch AFM experiment. (f) Evolution of poly(FcIL) film thickness as function of polymerization time for the SI-ATRP.

(4) FIG. 3. CV characterization of modified electrode in acetonitrile solution containing 0.1 M Bu.sub.4NBF.sub.4 at scan rate 0.1 V.Math.s.sup.1. The black curve represents the 1.sup.st cycle while the gray curve corresponds to the 20.sup.th cycle.

(5) FIG. 4. a) Dependency of peak current on reaction time at different reaction temperature (.diamond-solid.) 30 () 40 () 50 (x) 60 () 70 C. b) Plot of peak current variation as function of reaction temperature for 30 min SI-ATRP reaction time.

(6) FIG. 5. CV characterization of poly(FcIL)modified electrode in acetonitrile containing Bu.sub.4NBF.sub.4 0.1M, a) Scan rate 0.1, 0.2, 0.4, 0.6, 0.8 and 1 V.Math.s.sup.1. b) Scan rate 2, 5, 10, 30, 60 and 100V.Math.s.sup.1. c) Variation of anodic and cathodic peak current with the scan rate. d) Variation of the peaks potential with the scan rate (log plot).

(7) FIG. 6. a) CV characterization of modified electrode in 1-ethyl-2,3-dimethyl imidazolium TFSI, scan rate 0.1 V.Math.s.sup.1. b) Dependency of peak potential on scan rate.

(8) FIG. 7. CV response of poly(FcIL) deposited onto GC electrode in THF containing 0.1 M Bu.sub.4NBF.sub.4.

(9) FIG. 8. CV characterization of poly(FcIL) modified GC electrode in ACN without supporting electrolyte.

(10) FIG. 9. (A) Contact angles obtained for poly(FcIL) deposited onto Au substrate before and after electrochemical oxidation. (B) (a) Cyclic voltammogram of poly(FcIL) modified GC in PBS solution, (b) CV of bare GC in PBS solution containing 10.sup.4 M of tyrosine, (c) CV of poly(FcIL) modified GC in PBS solution containing 10 M of tyrosine. Scan rate 0.1 V.Math.s.sup.1.

(11) FIG. 10: Plot reporting the dependence between the measured current and the applied potential E=E.sub.i+vt, with: E=Applied potential at the instant t; E.sub.i=Initial potential; E.sub.1=Inversion potential; E.sub.f=Final potential; v=scan rate; t: time.

(12) FIG. 11: Cyclic voltammetry response of carbon electrodes in aqueous solution containing 0.1 M of HTFSI. Bare electrode (dash line), modified electrode (solid line)experiment corresponding to the 7th line of table 1 of example 2.

(13) FIG. 12: UV-Visible spectrum of the aqueous solution containing 1 mM of N-Ferrocenylmethyl-N-ethyleneamidoanthraquinoneimidazolium TFSI and 0.1 M of HTFSI before (dash line) and after (solid line) electrolysis.

(14) FIG. 13: Cyclic voltammetry response of carbon electrodes in 0.1 M of EMITFSI in MeCN. Absence (dash line) and presence (solid line) of electroactive molecule (1 mM de N-Ferrocenylmethyl-N-ethyleneamidoanthraquinoneimidazolium). Experiment corresponding to the 2nd line of table 1 of example 2.

(15) FIG. 14: Planar membraneless interdigitated electrodes for energy storage (supercapacitor or organic battery).

(16) FIG. 15: Cyclic voltammetry response of oxidative grafting of N-2-aminoethyl)-N-(4-nitrophenylethylimidazolium) bromide onto glassy carbon electrode, scan rate 0.1 V/s (example 4).

(17) FIG. 16: Cyclic voltammetry response of carbon modified electrode in 0.1 M H.sub.2SO.sub.4. Scan rate 0.1 V.Math.s.sup.1 (example 4).

(18) FIG. 17: CV of 1 mM of N-cobaltoceniumacetyl-N-vinylimidazolium in MeCN containing 0.1 M of LiClO.sub.4-imidazolium based molecule in solution using a GC electrode (example 6.1).

(19) FIG. 18: CV of Poly(N-cobaltoceniumacetyl-N-vinylimidazolium) modified GC electrode in MeCN containing 0.1 M LiClO.sub.4 (example 6.2).

(20) FIG. 19: CV of Poly(1-allyl-1-(2-(1-ferrocenylmethyl-H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium) modified GC electrode in MeCN containing 0.1 M LiClO.sub.4 (example 6.3).

(21) FIG. 20: (a) Cyclic voltammetry recorded at glassy carbon (GC) electrode of Fc quaternary ammonium at 1 mM in acetonitrile electrolytic solution, scan rate 0.1 V/s. (b) CV's at different scan rates from 0.02 to 0.1 V/s. (c) Plots of the peaks current as function of v.sup.1/2. (d) CV's of undiluted redox monomer ionic liquid and diluted in acetonitrile, scan rate 0.1 V/s (example 8.1).

(22) FIG. 21: (a) Cyclic voltammetry response of the attached polymer, Poly(FcIL) onto GC electrode in acetonitrile solution containing 0.1 M Bu.sub.4NPF.sub.6, 0.1 V/s. (b) CV's of the GC polymer electrode recorded at different scan rate from 1 to 50 V/s (the inset represents the CV's recorded between 0.1 and 1 V/s). (c) CV responses of the polymer In acetonitrile free of electrolyte. (d) Fe(2p) XPS high resolution spectrum recorded on the polymer (example 8.2).

(23) FIG. 22: Contact angles obtained for Poly(N-allyl-N,N-dimethyl-N-ferrocenylommonium) deposited onto ITO (indium tin oxide) substrate before and after electrochemical oxidation and anions exchanges (example 8.2).

(24) FIG. 23: Cyclic voltammetry response of 1 mM of 1-allyl-1-((N,N-dimethyl-N-ferrocenylmethylammonium)-acetyl)-[4,4-bipyridine]-1,1-diium in MeCN containing 0.1 M of LiClO.sub.4-GC electrode-quaternary ammonium based molecule in solution (example 8.3).

EXAMPLES

(25) The present invention will be illustrated through the following examples, which are not to be construed as limiting the scope of the invention in any way.

(26) Electrochemical Characterization:

(27) Cyclic voltammetry (CV) Is an electrochemical technique which is used to study the redox properties of chemical electro-active compounds at the interface of electrode in a solution. This technique is based on sweeping a linear and controlled potential at a given scan rate for a stationary or rotating electrodes. The obtained signal with this technique is the faradic current, i.e. the current due to the oxydo-reduction of electro-active species in solution or immobilized at the surface of electrode.

(28) A three electrodes system is necessary for using this technique, a reference electrode, a working electrode and an auxiliary electrode. Supporting electrolyte is always added into the solution to keep a sufficient conductivity. The potential is measured with the working electrode and the reference electrode while the current is measured with the working electrode and the auxiliary electrode. The data at each instant are reported in order to plot the dependence between the measured current and the applied potential (see FIG. 10).

Example 1: Imidazolium-Based Ionic Liquids and Polymeric Ionic Liquid of the Invention Containing a Ferrocene Group as the Oxidizable Group

(29) Chemical.

(30) Pentamethyl-diethylenetriamine (PMDETA), CuCl, CuCl.sub.2, LiTFSI, 2-bromoethyl methacrylate, imidazol, ferrocenylmethyl-trimethylammonium iodide, bromoethane, 4-methoxyphenol, tetrabutylammonium tetrafluoroborate from Aldrich were used as received. Solvent such as N,N-dimethylformamide, acetonitrile, dichloromethane were purchased from Aldrich. Ultrapure water (Millipore, resistivity 18.2 M.Math.cm) was obtained in the laboratory.

(31) Synthesis of Ionic Liquid and Polymeric Ionic Liquid.

(32) ##STR00047##

(33) 1-Ethyl-2,3-dimethylimidazolium Bis(trifluoromethane) sulfonimide, EdMI-TFSI, ionic liquid was prepared following the previously published procedures (Park et al. J. Org. Chem. 2001, 66, 8395-8401). The synthesized RTILs were dried under vacuum pumping overnight and the amount of residual water was measured with Karl Fischer titration (Karl Fischer 652 Metrohm) and found to be below 50 ppm.

(34) For the synthesis of monomer ionic liquid, the 2-bromoethyl methacrylate was first synthesized according to the previously published procedure. Next to that, N-(ferrocenylmethyl) imidazole was synthesized by adding ferrocenylmethyltrimethylammonium iodide (52 mM) and imidazole (64 mM) in dimethylformamide (according to the procedure of Forgie et al. Phys. Chem. Chem. Phys. 2013, 15, 7713-7721).

(35) In a second step, 2-Bromoethyl methacrylate (0.01 M) was mixed with N-(ferrocenylmethyl) imidazole (0.02 M) in the presence of inhibitor 4-methoxyphenol in 20 ml acetonitrile. The mixture was stirred at 40 C. for 24 h under N.sub.2 atmosphere, following that the mixture is diluted in CH.sub.2Cl.sub.2 and re-precipitated in diethyl ether in an ice bath and then filtered through a silica gel column, leading to the generation of ionic liquid based monomer. Finally, anion exchange reaction was performed by adding to the 3-(2-methacryloyloxy ethyl)-1-(N-(ferrocenylmethyl) imidazolium bromide (0.01 M) lithium bis(trifluoromethylsulfonyl)imide LiTFSI (0.012 M) in deionized water. The ionic liquid monomer was washed with water then mixed with dichloromethane and charcoal. This solution was purified through aluminium oxide layer, and then dried over MgSO.sub.4. After that, the trace of water was removed by vacuum pump overnight to afford 3-(2-methacryloyloxy ethyl)-1-(N-(ferrocenylmethyl) imidazolium bis(trifluoromethylsulfonyl)imide, as a brown viscous liquid. .sup.1H NMR (400 MHz, DMSO) : 1.90 (s, 3H), 3.71 (t, J=5.6 Hz, 2H), 4.16 (t, J=2.0 Hz, 2H), 4.19 (s, 5H), 4.32 (t, J=2.0 Hz, 2H), 4.44 (t, J=5.6 Hz, 2H), 4.93 (s, 2H), 5.74 (t, J=1.6 Hz, 1H), 6.08 (s, 1H), 6.92 (s, 1H), 7.22 (s, 1H), 7.82 (s, 1H). .sup.19F NMR (DMSO): 78.7 (s, 6F). More detail about the synthesis are reported in the Supporting Information.

(36) Immobilization of Initiator Layer.

(37) Bromide-terminated substrates were generated from the electrochemical oxidative grafting of 2-bromoethylamine onto glassy carbon (GC), Indium Tin Oxide (ITO), or on Au electrodes. The grafting was performed by chronoamperometry at potential 1.2 V vs SCE during 200 s. After the electrochemical modification the substrates were rinsed and sonication in water during 10 min.

(38) SI-ATRP Procedure.

(39) The procedure for polymerization of 3-(2-methacryloyloxy ethyl)-1-(N-(ferrocenylmethyl) imidazolium is as fellow. A mixture of 2 mM of the monomer [MAEImMFc][TFSI] and ligand pentamethyl-diethylenetriamine, PMDETA, (1.2 L) in solvent ionic liquid [EMIm][TFSI] was added to a dried Schenk flask. Next, the catalyst, Cu.sup.ICl (4 M), and the deactivator, Cu.sup.IICl.sub.2 (1.4 M), were introduced. The initiator-modified electrodes were immersed into the reaction mixture under argon flow. For the SI-ATRP, different temperatures reactions were used, 30, 40, 50, 60 and 70 C.

(40) Surface Analyses.

(41) XPS measurements on generated polymer redox ionic liquid were performed using a Thermo VG Scientific ESCALAB 250 system fitted with a micro-focused, monochromatic Al K (hv=1486.6 eV) 200 W X-ray source. For XPS investigations the polymers were supported on indium tin oxide (ITO) substrate, and the electrodes are systematically rinsed and then sonicated during 10 min to remove the weakly adsorbed molecules.

(42) The morphology and the thickness of the poly(FcIL) were investigated using AFM experiments in tapping mode were recorded at room temperature with a Molecular Imaging PicoPlus. The thickness of the generated polymer layers onto Au substrate was determined by ellipsometry on a SENTECH SE 400adv ellipsometer.

(43) Electrochemical Measurements.

(44) Three-electrode cell was used for the electrochemical measurements. Platinum wire and saturated calomel electrode, SCE, were used as auxiliary electrode and reference electrode, respectively. The electrochemical measurements were recorded using a CHI 660C potentiostat (CH Instruments, made in TX, USA).

(45) Results and Discussion

(46) The SI-ATRP process for the elaboration of polymer brushes onto electrode surface is based on the immobilization of thin initiator layer. The first step is to carry out an electrochemical oxidation of 2-bromoethylamine onto electrode surface. This process yielded a bromide terminated layer strongly attached onto the electrode. Following that, the attached initiator layer was immersed in ionic liquid, [EMIm][TFSI], containing the redox ionic liquid monomer, [MAEImMFc][TFSI], and all the necessary reagent for the SI-ATRP as presented in the experimental section.

(47) The first SI-ATRP experiment was performed onto ITO substrate at 50 C. using 30 min polymerization time. To confirm the successful growth of the polymer redox ionic liquid, chemical surface composition was analyzed by X-ray photoelectron spectroscopy (XPS), and the obtained results are summarized in FIG. 1.

(48) The inset in FIG. 1 displays the survey spectrum of the polymer modified ITO electrode which shows mainly the contribution of C.sub.1s and O.sub.1s, as well as N.sub.1s signals, in agreement with the element composition of the redox polymer ionic liquid. Small signals corresponding to In.sub.3d and Sn.sub.3d are also visible. The intensity attenuation of the In.sub.3d (at 445 eV) and Sn.sub.3d (at 487 eV) XPS signals, compared to unmodified ITO, is an indication of the covering of ITO by the polymer. Deep analysis of the XPS measurements through the investigation of high-resolution element scans of C.sub.1s, N.sub.1s, Fe.sub.2p, and F.sub.1s signals reveal several features. The C(1s) high resolution spectrum shows the presence of two peaks components at 287 and 285 eV attributable to amide bands and aromatic carbon, respectively. The peak observed at 289.4 eV is related to the contribution of CO component. The N(1s) spectrum displays two defined components at 400 and 402.4 eV respectively attributed to nitrogen bonded to sulfonyl groups and to imine group in the imidazolic ring. Additional peak at 690 eV is observed and attributed to F(1s). Finally, the presence of two peaks at 708.6 and 721.1 eV, is a signature of the presence of Fe element in the form of ferrocene. The analysis of the FTIR spectrum shows peaks at 1740 and 1260 cm.sup.1 ascribed to CO and CO stretching vibrations modes In the ester group. The peak around 1148 cm.sup.1 was assigned to the CN stretching of the imidazolium side chain, while the peaks at 1646 and around 1456 cm.sup.1 are attributed to the ring vibration of imidazolium. The small peaks located at 1410, 1103 and the sharp peak at 1066 cm.sup.1 are characteristic for the ferrocene group. On the high wavenumber zone, the peaks centered at 2925 and 2855 cm.sup.1 are ascribed to the asymmetric and symmetric stretching of CH, respectively, in the polymer backbone, while the bands In the region of 3650 cm.sup.1 are due to the vibrations mode for TFSI anion. Overall, XPS and FTIR investigations confirm the immobilization of polymer ferrocene ionic liquid, poly(FcIL), and the presence of the TFSI anion.

(49) ##STR00048##

(50) Surfaces analyses of polymer modified electrode were complemented by AFM investigations and ellipsometry measurements as shown in FIG. 2.

(51) FIG. 2a shows the topography image of the attached initiator layer onto gold surface. This image reveals homogeneous morphology, the average roughness is around 0.5 nm and the thickness is around 1.5 nm. The same morphology was observed on different area of the sample indicating the homogeneity of the layer. After the performance of the SI-ATRP polymerization the surface was characterized by SEM and AFM images. The SEM image clearly shows two distinct zone, the bright area which represents the unmodified Au and dark area corresponding to the attached poly(FcIL). FIGS. 2c and d illustrate a typical 2D and 3D AFM topographic scan of the polymer. The 2D image shows a morphological change when compared to unmodified substrate. The image, FIG. 2c, exhibits a grainy structure with an alignment of the grain on 1D direction (blue line) demonstrating a self-reorganization of the polymer based ionic liquid. To confirm this morphology, the same area was scanned using 45 scan angle as shown in FIG. 2d. As a consequence, the alignment of the grain is still visible (red line) but twisted by 45 compared to the initial image. This experiment confirms that the observed alignment is due to the self-organization of the deposited polymer and not to the tip imaging artefacts. The polymer units on the surface exhibit a brush-like structure as illustrated in the 3D representation (FIGS. 2c and 2d). These investigations suggest that the i-ATRP has given rise to a dense coverage of polymer brushes on the surface. FIG. 2e shows the cross section of the generated hole by scratch AFM experiment and an average thickness of 12 nm is measured.

(52) One of the parameter that controls the polymer thickness in the SI-ATRP is the polymerization time reaction. The SI-ATRP was performed onto Au substrate using the same condition as described above but with different polymerization time reaction 15, 30, 60, 90 and 120 min. The thickness of the film was measured for each reaction time by ellipsometry and the obtained results are presented in FIG. 2f. The curve shows an initial increase of the polymer thickness as function of the polymerization time. After, 1 h polymerization time reaction the thickness reach a maximum value around 20 nm and cease to growth suggesting the limited access of monomer to surface. Similar tendency has been reported in the literature. The measured thicknesses by AFM were in perfect agreement with ellipsometry measurements. Compared to the measured thickness, in classical solvent, as function of the polymerization time, the polymerization rate in ionic liquid is higher than that observed in the classical solvents. This effect has been already reported and was attributed to the polarity of ILs. Despite this effect, the measured thickness of the poly(FcIL) Is in the same range as that reported for other poly(IL).

(53) To obtain insights on the redox properties of the polymer, the electrochemical characterization of poly(FcIL) become straightforward as the attached polymer contain electroactive units, ferrocene, which could be easily characterized by cyclic voltammetry (CV). SI-ATRP was performed onto GC electrode at 50 C. using 60 min reaction time. FIG. 3 displays the electrochemical response of the poly(FcIL) deposited onto GC electrode In acetonitrile electrolytic solution.

(54) The CV shows oxidation and reduction waves with standard potential at 0.57 V vs SCE, this redox signal is attributed to the electrochemical response of the Fc.sup.+/Fc redox couple. The peak-to-peak potential is almost 0 V confirming the attachment of the Fc species onto the electrode surface. The electrochemical response of Fc units enables the estimation of the surface coverage using the formula =Q/nFA, where Q is the charge of the anodic peak, n is the number of the electrons for the oxidation of the attached Fc units, F the Faraday's constant and A represent the area of the electrode. The average value of the surface coverage was found to be around 410.sup.9 mol.Math.cm.sup.2. Pyun and co-workers have investigated the polymerization by SI-ATRP of ferrocene functional polymer brushes and they demonstrate a linear correlation between the surface coverage and the molecular polymer weight of polyferrocenyl methacrylate deposited on electrode surface (see Kim et al. Langmuir 2010, 26, 2083-2092). Based on their results, the expected molecular weight of the polymer with a surface coverage of about 410.sup.9 mol.Math.cm.sup.2 is 10,000 g/mol. Thus, assuming the applicability of this relation to our system, the average grafting densities of the poly(FcIL) brushes could be estimated in the range of 0.3 to 0.8 chains/nm.sup.2. FIG. 3 demonstrates that after repetitive CV the electrochemical signal remains unchanged (gray curve) suggesting the stability of the attached ferrocene. This finding leads to conduct further electrochemical studies based on the variation of the Fc.sup.+/Fc peaks current.

(55) In the following, the SI-ATRP in ionic liquid was performed using various reaction time and various temperatures. In order to compare the impact of the polymerization time and the temperature in the SI-ATRP process, the variation of the Fc.sup.+/Fc peaks current was followed. FIG. 4a illustrates the evolution of the oxidation peak current of the attached Fc as function of the reaction time and the temperature. One has to note that each point in the FIG. 4 is an average of 10 distinct experiments.

(56) The curve shows that whatever the used temperature the tendency is that the peak current increases fast initially with the polymerization times to attain an asymptotic value after 30 min. The observed saturation after 30 min polymerization time could be due to the termination reaction of the SI-ATRP process or to the limit of the electrochemical detection of ferrocene unit. This nonlinearity feature is consistent with the ellipsometry results shown in FIG. 2d, and suggests probably the termination of the SI-ATRP process after 30 min reaction time under our experimental conditions. FIG. 4b displays the variation of oxidation peak current of ferrocene as function of temperature for fixed reaction time (30 min). For low temperature, the curve shows increases of the peak current with the temperature and reaches a maximum at 50 C., then for higher temperature the peak current decreases. Form these investigations it appears that the optimal conditions for the SI-ATRP of the redox ionic liquid monomer in ionic liquid media are 30 min reaction times at 50 C. In the following these optimum reaction conditions will be used.

(57) The electrochemical investigations were complemented by recording the CV of the modified electrode at different scan rate as illustrated in FIG. 5.

(58) FIGS. 5a and b shows series of cyclic voltammograms of Poly(FcIL) brushes deposited onto GC electrode performed at different scan rates. For lower scan rate (<1 V.Math.s.sup.1), the Fc.sup.+/Fc redox signal is clearly visible with a peak potential separation close to 0 V. The full-width at half maximum (fwhm) is around 100 mV, this value is slightly higher than 90 mV predicted theoretically (Bard, A. J.; Faulkner, L. R. Electrochemical methods. Fundamentals and Applications; Wiley; New York, N.Y., 1980; p. 522), suggesting the occurrence of weak lateral interaction of ferrocene moieties within the polymer structure. In addition, linear variation of the peak current versus the scan rate is observed (FIG. 5c), suggesting the presence of non-diffusive process demonstrating that the Fc species are attached onto the GC electrode. However, for higher scan rate (above 1 V.Math.s.sup.1) the redox signal of ferrocene starts to deviate from fully reversible system (FIG. 5b and FIG. 5d). FIG. 5d shows that the peak potential remains unchanged for lower scan rate. However, further increase of the scan rate induces variation of the peaks potentials in positive and negative direction suggesting the limitation of the redox process by the rate of electron transfer of attached Fc in the polymer film. From this curve and based on Laviron's model one could estimate the apparent rate constant of electron transfer (Laviron et al. J. Electroanal. Chem. 1979, 101, 19-28).
k.sub.a.sup.app=(1.sub.a)nFv.sub.a/RT; k.sub.c.sup.app=.sub.cnFv.sub.c/RT

(59) The charge transfer coefficient (a) was determined from the respective slopes of the linear portion of the Ep vs Log(v) plot, at high scan rates, and a value of 0.6 and 0.4 were obtained for the anodic and cathodic coefficient transfer, respectively. In the present case, the measured average of the apparent rate constants is 160 s.sup.1. This value has to be compared to that measured for neutral Fc units covalently attached onto electrode material which are ranged from 0.1 to 200 s.sup.1 (Fabre et al. J. Phys. Chem. B. 2006, 110, 6848-6855). The disparity of the reported electron transfer rate value is mainly related to the organization of the Fc units onto the surface, to the surface density and to the selected method for the grafting. In our case, the value of the reported apparent electron transfer rate could be considered as very fast which could be explained by several features. Indeed, the measured rate is a contribution of electron tunneling, through the thin initiator layer acting as insulating barrier (for attached ferrocene located at distance less than 5 nm from the electrode), and also electron hopping between the ferrocene units located beyond the tunneling distance. Other parameters could enhance the electron transfer including the organization of Fc units within the polymer brushes like structure, the short distance of the initiator and the chemical composition of the polymer which includes a positive and negative charge of the ionic liquid based structure. The electron transport mechanism process through the initiator and brush layers containing Fc units has been described in the literature. Thus, for the Fc units located near the electrode surface (5 nm distance) the electron transport may occur across the initiator layer through diffusion of polymer bound ferrocene and/or pinholes or defects within the polymer brushes or by tunneling. However, for Fc unit located at distance higher than the tunneling distance the electron transfer process is mainly governed by hopping mechanisms or electron exchange within the polymer structure. Indeed, we believe that the presence of positive and negative charges within the film may enhance the electron hopping process and consequently the electron transfer rate.

(60) In this part, the electrochemical investigations of the poly(FcIL) modified electrodes were performed in ionic liquid media. FIG. 6a displays the recorded CV of poly(FcIL) supported GC electrode in ionic liquid, while FIG. 6b represent the dependency of the peak potential as function of the scan rate.

(61) The characterization in ionic liquid of the modified electrode exhibits similar behavior as that observed in acetonitrile solution (see FIG. 3). Indeed, a reversible redox system corresponding to Fc.sup.+/Fc redox couple is observed at 0.57 V. The difference between the anodic and cathodic peak potential is almost 0 V indicating the presence of immobilized system. However, when compared to the response in ACN solution the peak current is 3 times lower in ionic liquid. As consequence, it appears that the surface concentration of immobilized Fc in ionic liquid is lower than that obtained in ACN for the same electrode; however, one has to consider the effect of the ionic liquid viscosity and direct comparison could not be conducted. Such difference could be linked to the ionic liquid viscosity, to the solvation of attached layer in ionic liquid media compared to acetonitrile, and to the electrostatic interaction between attached imidazolium and the imidazolium based ionic liquid.

(62) FIG. 6b shows the dependency of the oxidation peak potential variation with the scan rate. As expected, no variation of the peak potential is observed for low scan rate. However, the increase of the scan rate induces a positive deviation of peak potential suggesting control of the redox process by the rate of electron transfer. More interestingly, the apparent rate constant measured in ionic liquid was found to be similar to that measured in ACN media. In general, for redox species dissolved in ionic liquid solution the apparent electron transfer constant is lower by 1 to 2 orders of magnitude compared to classical solvent; however, in our case and for attached species this constant appears to be not affected by the used solvent and less sensitive to the solvation. Such behavior could be linked to the presence of positive (imidazolium ring) and negative (TFSI) charge within the film, which could be considered as self-solvation or self-double layer of the poly(FcIL) modified electrode.

(63) In order to confirm the role of ionic moieties in the electrochemical response, further investigations of poly(FcIL) were conducted in THF electrolytic solution (see FIG. 7).

(64) The CV shows clear reversible redox process related to the Fc.sup.+/Fc redox couple with a peak potential separation almost close to 0 V. This behavior has to be compared with the electrochemical response of neutral redox polymer modified electrode, poly-ferrocene methacrylate (PFcMA), in THF electrolytic solution. In the presence of THF as solvent, the electrochemical response of neutral poly(Fc) polymer brushes film exhibits large peak potential separation suggesting that the redox process is restricted by rate of counter-ion migration into/out of the polymer. However, in our case, the electrochemical response of poly(FcIL) in THF is similar to that recorded in ACN without a visible change in the peak to peak potential separation. This difference, when compared to neutral redox polymer film, is probably linked to the presence of ions (cation and anion in polymer ionic liquid) within the film which maintains the fast electron transfer rates between adjacent Fc units. This result highlights the advantage of the formation of redox polymer ionic liquid in electrochemical system.

(65) Based on the above results, the electrochemical characterization of the generated material was investigated in solvent free of supporting electrolyte. The CV of poly(FcIL) modified electrode recorded in the absence of supporting electrolyte is shown in FIG. 8.

(66) The curve shows anodic and cathodic peaks of Fc.sup.+/Fc redox couple. Compared to the electrochemical signal recorded in the presence of supporting electrolyte the peak current is lowered and the peak potentials are shifted to more positive potential. The decrease in the peak current is expected since no ions are present in the solution and could be related to the presence of silent Fc groups that are not detected during the electrochemical measurement. The positive peak potential shift has already been reported when investigating the influence of supporting electrolyte concentration on the response of neutral redox polymer. It was found that it is more difficult to oxidize neutral redox polymer film in the presence of low supporting electrolyte concentration. However, in the present example there is no supporting electrolyte In the solution and the electrochemical signal is still visible. One has to note that the electrochemical characterization of neutral polymer brushes, poly(FcMA), In acetonitrile solution free of electrolyte does not show any electrochemical signal (data not shown). The presence of the electrochemical signal in solvent free electrolyte confirms that the poly(FcIL) could act as self-supporting electrolyte thanks to the presence of imidazolium cation and the TFSI anion within the film.

(67) Stimuli-responsive polymers brushes are particularly interesting materials that have been used for several applications including electrochemical devices, sensors, microfluidic devices and surface wettability. In the following, the generated poly(FcIL) has been investigated for potential use in their capability of reversible electrochemical-switch of the surface wettability and for bio-catalytic activity.

(68) The modulation of the properties of interfaces such as the variation of the wettability is of high interest. The best advantage of using electrochemistry as an external stimulus is its ability to switch the surface oxidation state in a few second or less. FIG. 9A shows the contact angle for the poly(FcIL) attached onto Au substrate before and after electrochemical oxidation. Oxidation of the ferrocene based polymer was achieved electrochemically by applying a potential of about 0.7 V during 10 seconds in ACN solution containing 0.1 M LiTFSI as supporting electrolyte. Contact angle (CA) measurements were performed for four different samples and the poly(FcIL) interface shows an average contact angle of about 90 indicating the hydrophobic character of the surface. This result is in accordance with previously reported results on poly(IL). Interestingly, after electrochemical oxidation the CA decreases to 60 suggesting the presence of hydrophilic surface. This AA of about 30 suggests the possibility to perform electro-switchable wettability, and this switching appears to be reversible upon several oxidation reduction processes. The poly(FcIL) could be used as stimuli responsive polymer with a reversible electrochemical switchable wettability. This property could be coupled with the possibility to perform counterions (anions) exchanges within the polymer based ionic liquid films, which may lead to further drive the transition between hydrophobicity and hydrophilicity of the surfaces.

(69) As stated above, poly(IL) and redox polymer have been used in several applications including sensor. In the following, the electrochemical response of L-tyrosine on poly(FcIL) modified GC electrode was investigated. Tyrosine was chosen as test molecules since it is an important component of proteins, and is indispensable in human nutrition. As Tyrosine is an electroactive molecule, electrochemistry has been proposed as method for its detection in different media. Nevertheless, the low electroactivity, the slow electron transfer rate combined with the high oxidation over potential of tyrosine provide ill-defined electrochemical system. To overcome these limitations, the use of modified electrodes as electrochemical sensor has been proposed to improve the electrochemical detection of tyrosine.

(70) FIG. 9Ba shows the electrochemical response of poly(FcIL) modified GC in PBS solution. The curve displays a redox electrochemical signal corresponding to Fc redox couple of the poly(FcIL). The shape of the CV recorded in PBS solution is similar to that observed in acetonitrile electrolytic solution. FIG. 9Bb displays the response of bare GC electrode in in PBS solution containing 10.sup.4 M tyrosine. As expected, the curve shows clearly that the oxidation peak (around 0.8 V/SCE) of tyrosine is ill-defined. However, the electrochemical signal of tyrosine onto poly(FcIL) modified GC electrode (FIG. 9Bc) was considerably improved as attested by the peak potential shift to less positive value, the oxidation peak current become sharper and increased significantly. Compared to bare GC electrode, the potential shift, to less positive potential, of about 120 mV indicates that the modified electrode shift the over-potential negatively. This result associated with the increase of the anodic peak current evidenced that the poly(FcIL) improves the oxidation of tyrosine.

CONCLUSION

(71) In summary, this work presents the first example of redox active poly(ionic liquid) directly grafted onto electrode surface using surface-initiated ATRP. Surface investigations of the generated material clearly confirm the immobilization of poly(FcIL) and the presence of the TFSI anion within the attached polymer, while AFM images reveal the formation of a well-defined polymer brushes like structure. The electrochemical characterizations of poly(ferrocenyl ionic liquid) modified electrode in electrolytic acetonitrile solution show the presence of a reversible redox signal. Besides that, the electrochemical analyses reveal that the redox behavior is characteristic of surface-confined electroactive layers. Unlike neutral poly(Fc), and thanks to the presence of ionic moieties in the poly(FcIL) the oxidation/reduction of the Fc units is not restricted by the rate of counter-on migration into/out of the polymer. This finding is supported by the observation of the ferrocene electrochemical signal when using solvent free electrolyte. Finally, the poly(FcIL) modified electrodes have been successfully used as reversible redox responsive materials as attested by the reversible electrochemical switchable wettability of the polymer. In addition, the generated polymer based redox ionic liquid exhibits excellent electrocatalytic activity and voltammetric response towards tyrosine. These properties would promote the potential useful of poly(redox ionic liquid) in electrochemical sensor and microfluidic applications.

Example 2. Ionic Liquids Comprising Anthraquinone Groups as the Reducible Group

2.1. Synthesis of N-Ferrocenemethyl-N-ethyleneamidoanthraquinoneimidazolium bis(trifluoromethylsulfonyl)imide

(72) ##STR00049##

(73) The synthesis was performed in 4 steps

1st Step: Synthesis of Chloroethyleneamidoanthraquinone

(74) ##STR00050##

(75) In a three necked flask, 2-aminoanthraquinone (1.0 g, 4.5 mmol), pyridine (0.5 ml, 6.2 mmol) and 60 ml of dichloromethane were mixed under vigorous stirring at 0 C. Solution of chloroacetylchloride (0.4 ml, 5.4 mmol) in 20 ml of dichloromethane was then added drop wise. After stirring 4 h, the solution was filtered and extracted with 20 ml HCl 3M. The organic layer was washed with 20 ml of saturated NaCl and recovered by decantation. A large amount of MgSO.sub.4 was added into the organic phase in order to eliminate water traces. The solvent was evaporated to obtain a brown residue. The crude product was further dissolved in 100 ml of dichloromethane and 100 ml of hexane was slowly added into the solution. The purified product was recrystallized in the mixture and then was filtered and dried under vacuum.

(76) Yield: 42.7% (0.55 g)

(77) 1H RMN (CDCl.sub.3) : 4.27 (s, 2H), 7.82 (m, 2H), 8.23 (d, J=2.4 Hz, 1H), 8.32 (m, 4H), 8.6 (s, 1H)

2nd Step: Synthesis of N-ferrocenylmethylimidazole

(78) 25 g of trimethylammonium ferrocene iodide (64.8 mmol, 1 equiv.) and 5.4 g of imidazole (79 mmol, 1.22 equiv.) were dissolved in 140 ml of dimethylformamide (DMF). The solution was refluxed for 2 hours. Then 150 ml of distilled water was added into the balloon and the black solid precipitate was eliminated by filtration. The product was recovered by decantation with diethyl ether (3100 ml). The organic layer was washed 1 time with distilled water (100 ml) in order to eliminate DMF traces. The organic phase was dried with MgSO.sub.4. Diethyl ether was evaporated to obtain orange powder.

(79) Yield: 45% (8.23 g)

(80) 1H NMR (DMSO): 4.15 (t, J=2.0 Hz, 2H), 4.18 (s, 5H), 4.31 (t, J=2 Hz, 2H), 4.90 (s, 2H), 6.83 (s, 1H), 7.15 (s, 1H), 7.64 (s, 1H).

3rd Step: Synthesis of N-Ferrocenemethyl-N-ethyleneamidoanthroquinoneimidazolium Iodide

(81) ##STR00051##

(82) 0.1 g of chloroethyleneamidoanthraquinone (0.33 mmol) was mixed with 0.094 g of N-ferrocenylmethylimidazole (0.35 mmol) and a catalytic amount of sodium iodide in 20 ml of acetone/dichloromethane (50:50 v/v).

(83) The reaction was performed under vigorous stirring at room temperature for 60 hrs. Then the product was recovered by filtration and washed with distilled water. The brown powder was obtain and dried under vacuum for 1 day.

(84) Yield: 69.5% (0.13 g). 1H RMN (CDCl.sub.3) : 4.27 (m, 7H), 4.46 (t, J=2 Hz, 2H), 5.26 (s, 2H), 5.28 (s, 2H), 7.82 (s, 1H), 7.91 (s, 1H), 8.04 (m, 2H), 8.2 (m, 1H), 8.24 (m, 3H), 8.47 (m, 1H), 9.15 (s, 1H), 11.18 (s, 1H).

4.SUP.th .Step: Synthesis of N-Ferrocenemethyl-N-ethyleneamidoanthroquinoneimidazolium TFSI

(85) ##STR00052##

(86) 0.13 g of N-Ferrocenemethyl-N-ethyleneamidoanthraquinoneimidazolium iodide (0.25 mmol) was added into a solution containing 20 ml of distilled water and 0.2 g of lithium bis(trifluoromethylsulfonyl)imide (0.75 mmol). The solution was then heated at 70 C. for 24 hours in order to obtain a brown powder. The product was washed thoroughly with distilled water and dried under vacuum for 1 day.

(87) Yield: 87% (0.17 g)

(88) 1H RMN (CDCl.sub.3): 4.27 (m, 7H), 4.45 (t, J=2 Hz, 2H), 5.26 (s, 2H), 5.28 (s, 2H), 7.81 (s, 1H), 7.92 (s, 1H), 8.04 (m, 2H), 8.18 (m, 1H), 8.24 (m, 3H), 8.47 (m, 1H), 9.15 (s, 1H), 11.18 (s, 1H).

(89) 19F RMN: 78.88 (s, 6F)

(90) Via structural study by using NMR; the formation and the purity of the obtained product were confirmed.

2.2. Synthesis of N-ethyleneamidoanthraquinone-N-vinylimdazolium Iodide

(91) In the solution containing 1-vinylimidazole (0.094 g, 0.9 mmol) and a catalytic amount of sodium iodide (0.14 g, 1 mmol) in 20 ml de acetone/dichloromethane (50/50 v/v), chloroethyleneamidoanthraquinone (0.27 g, 0.9 mmol) was added. The mixture was kept under stirring at room temperature for 1 day. After the reaction, the precipitate was filtered and washed 5 times with distilled water. The crude product was further recrystallized in a solution of dichloromethane/hexane and the purified one was appeared as brown powder.

(92) Yield: 94% (0.3 g).

(93) 1H RMN (DMSO): 5.39 (s, 2H), 5.5 (m, 1H), 6.05 (m, 1H), 7.47 (q, J=8.8 Hz, 1H), 7.82 (s, 1H), 7.9 (s, 1H), 7.93 (m, 2H), 8.08 (m, 1H), 8.22 (m, 3H), 8.29 (d, J=2 Hz, 1H), 9.52 (s, 1H), 11.53 (s, 1H).

(94) ##STR00053##

2.3. Synthesis of N-anthroquinoneferrocenemethyl-N-allylimidazolium

1.SUP.st .Step: Synthesis of N-ferrocenylmethyl-N-allylimidazolium Bromide

(95) 1.2 g of Ferrocenylmethylimidazole (8.76 mmol, 1 equiv.) previously synthesized was dissolved in 40 ml of chloroform. Then, 0.91 ml of allylbromide (10.5 mmol, 1.2 equiv.) was added slowly to the solution of ferrocenemethylimidazole under stirring. The mixture was refluxed for 2 h. Finally, the solvent and non-reacted allylbromide were eliminated by evaporation under reduced pressure. The product was dried under vacuum for 1 day. The title compound is obtained as a very viscous brown oil in 90% yield (2.04 g).

(96) ##STR00054##

(97) 1H RMN (DMSO) : 4.22 (m, 7H), 4.45 (t, J=1.6 Hz, 2H), 4.83 (m, 2H), 5.26 (s, 2H), 5.33-5.36 (m, 2H), 6.04 (m, 1H), 7.71 (s, 1H), 7.81 (s, 1H), 9.23 (s, 1H).

2.SUP.nd .Step: Synthesis of N-anthraquinoneferrocenemethyl-N-allylimidazolium

(98) Solution containing 3.5 mM de N-ferrocenemethyl-N-allyimidazolium in 10 ml of MeCN was mixed with a second solution containing 3.7 mM of anthraquinone diazonium salt dissolved in

(99) 10 ml of MeCN. The mixture was sonicated for 30 minutes and served to modify the electrodes.

(100) ##STR00055##

2.4. Synthesis of N-ethyleneamidoanthroquinone-N-methylimidazolium bis(trifluoromethylsulfonyl)imide

(101) ##STR00056##

1.SUB.st .Step: Synthesis of Chloroethyleneamidoanthaquinone

(102) In a two-necked flask, 2-aminoanthraquinone (1.0 g, 4.5 mmol), pyridine (0.5 mL, 6.2 mmol) and dichloromethane (60 mL) were mixed and stirred at 0 C. Solution of Chloroacetyl chloride (0.4 mL, 5.4 mmol) in dichloromethane (20 mL) was then added drop-wise. After stirring 4 h, the solution was filter and extracted with 20 mL HCl 3 M. The dichloromethane layer was washed with 20 mL saturated NaCl solution. The organic layer was then dried over anhydrous sodium sulfate. The solvent was then evaporated to obtain a brown residue. The crude product was further dissolved in 100 mL dichloromethane and 100 mL hexane was slowly added. The purified product was then filtered and dried under vacuum. Intermediate 10 is obtained as a brown crystalline solid in 54% yield (0.73 g).

(103) .sup.1H NMR (CDCl.sub.3): 4.27 (s, 2H, CH.sub.2), 7.82 (m, 2H, 2ArH), 8.23 (d, 2.4 Hz, 1H, ArH), 8.32 (m, 4H, 4ArH), 8.6 (s, 1H, NH)

2nd Step: Synthesis of N-ethyleneamidoanthraquinone-N-methylimidazolium Iodide

(104) To a solution of methylimidazole (0.11 g, 1 mmol) and a catalytic amount of sodium iodide in 15 ml Acetone/dichloromethane (50:50), chloroethyleneamidoanthraquinone (0.3 g, 1 mmol) was added and the mixture was stirred for 24 hr at room temperature. After reaction, the precipitate was filtered and then washed 5 times with distilled water. The crude product was then recrystallized in dichloromethane/hexane to obtain the brown powder. Intermediate 10 is obtained as a brown solid powder in 84% yield (0.29 g).

(105) .sup.1H NMR (DMSO): 3.94 (s, 3H, CH.sub.3), 5.34 (s, 2H, CH.sub.2), 7.76 (s, 1H, NCH), 7.78 (s, 1H, NCH), 7.95 (m, 2H, 2ArH), 8.07 (m, 1H, ArH), 8.22 (m, 3H, 3ArH), 8.52 (d, 2 Hz, 1H, ArH), 9.14 (s, 1H, NCHN), 11.43 (s, 1H, CONH).

3rd Step: Synthesis of N-ethyleneamidoanthraquinone-N-methylimidazolium bis(trifluoromethylsulfonyl)imide

(106) The ion exchange was occurred in aqueous media. Solution of LiTFSI (0.124 g, 0.47 mmol) in 5 mL distilled water was added dropwise to the Chloroethyleneamidoanthraquinone 1-methylimidazolium iodide (0.03 g, 0.1 mmol) in 0.1 mL DMSO. The mixture was stirred for 24 hrs at 70 C. After that, the solid product was filtered and washed with distilled water (420 ml) affording brown powder. The title compound is obtained as a brown powder in 20% yield (0.01 g).

(107) .sup.1H NMR (DMSO): 3.94 (s, 3H, CH.sub.3), 5.3 (s, 2H, CH.sub.2), 7.77 (s, 1H, NCH), 7.76 (s, 1H, NCH), 7.94 (m, 2H, 2ArH), 8.03 (m, 1H, ArH), 8.21 (m, 3H, 3ArH), 8.5 (d, 2 Hz, 1H, ArH), 9.11 (s, 1H, NCHN), 11.18 (s, 1H, CONH).

(108) .sup.19F NMR (DMSO): 78.73 (s, 6F, CF.sub.3).

2.6. Synthesis of N-ethyleneamidoanthraquinone-N-vinylimidazolium bis(trifluoromethylsulfonyl)imide

(109) ##STR00057##

1st Step: Synthesis of ethyleneamidoanthraquinone-N-vinylimidazolium Iodide

(110) This compound was synthesized using the protocol of N-ethyleneamidoanthraquinone-N-methylimidazolium iodide. To a solution of 1-vinylimidazole (0.094 g, 0.9 mmol) and a catalytic amount of sodium iodide (0.14 g, 1 mmol) in 20 ml Acetone/dichloromethane (50:50), chloroethyleneamidoanthraquinone 10 (0.27 g, 0.9 mmol) was added and the mixture was stirred for 24 hr at room temperature. After reaction, the precipitate was filtered and then washed 5 times with distilled water. The crude product was then recrystallized in dichloromethane/hexane to obtain the brown powder. Intermediate 16 is obtained as a brown solid powder in 94% yield (0.30 g) .sup.1H NMR (DMSO): 5.39 (s, 2H, CH.sub.2), 5.5 (m, 1H, CHCH.sub.2), 6.05 (m, 1H, CHCH.sub.2), 7.47 (q, 8.8 Hz, 1H, CHCH.sub.2), 7.93 (m, 2H, 2ArH), 8.08 (m, 1H, ArH), 8.22 (m, 3H, 3ArH), 8.29 (d, 2 Hz, 1H, ArH), 9.52 (s, 1H, NCHN), 11.53 (s, 1H, CONH).

2nd Step: Synthesis of N-ethyleneamidoanthraquinone-N-vinvlimidazolimbis(trifluoromethylsulfonyl)imide

(111) This compound was synthesized using the protocol of N-ethyleneamidoanthraquinone-N-methylimidazolium bis(trifluoromethylsulfonyl)imide. The ion exchange was occurred in aqueous media. Solution of LiTFSI (0.17 g, 0.6 mmol) in 5 ml distilled water was added drop-wise to the N-ethyleneamidoanthraquinone-N-vinylimidazolium iodide (0.179 g, 0.5 mmol) in 0.1 ml CH.sub.2Cl.sub.2. The mixture was stirred for 24 hrs at 70 C. After that, the solid product was filtered and washed with distilled water (420 ml) affording brown powder. The title compound is obtained as a brown solid powder in 86% yield (0.22 g). .sup.1H NMR (DMSO): 5.35 (s, 2H, CH.sub.2), 5.5 (m, 1H, CHCH.sub.2), 6.05 (m, 1H, CHCH.sub.2), 7.45 (q, 8.8 Hz, 1H, CHCH.sub.2), 7.94 (m, 2H, 2ArH), 8.05 (m, 1H, ArH), 8.21 (m, 3H, 3ArH), 8.50 (d, 2 Hz, 1H, ArH), 9.47 (s, 1H, NCHN), 11.52 (s, 1H, CONH).

(112) .sup.19F NMR (DMSO): 78.73 (s, 6F, CF.sub.3).

Example 3. Ionic Liquids Comprising Viologene Groups as the Reducible Group

3.1. Synthesis of 1-heptyl-1-(2-(1-ferrocenylmethyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium

1.SUP.st .Step: Synthesis of 1-heptyl-1-chloroacetyl-[4,4-bipyridine]-1,1-diium

(113) ##STR00058##

(114) In a three necked flask, 1-Heptyl-4-(4-pyridyl)pyridinium bromide (3.36 g, 10 mmol) was dissolved in 100 ml of distilled dichloromethane under vigorous stirring at 0 C. Solution of chloroacetylchloride (1.5 ml, 20 mmol) in 40 ml of dichloromethane was then added drop wise. After stirring 1 h, the solution was filtered yielded light yellow solid. The solid was then washed with dichloromethane and dried under vacuum.

(115) Yield: 99% (4.02 g)

2.SUP.nd .Step: Synthesis of 1-heptyl-1-(2-11-ferrocenylmethyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium

(116) ##STR00059##

(117) 1-heptyl-1-chloroacetyl-[4,4-bipyridine]-1,1-diium (0.45 g, 1 mmol) was mixed with N-ferrocenylmethylimidazole (0.32 g, 1.2 mmol) in 100 ml of distilled dichloromethane. The mixture was then heat for 24 hrs at 50 C. Then the solvent was distilled off under reduced pressure yielded highly viscous brown oil. The crude product was washed in n-hexane:dichloromethane (10:1, 3 times).

(118) Yield: 73% (0.52 g)

3.2. Synthesis of 1-allyl-1-(2-(1-ferrocenylmethyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium

1.SUP.st .Step: Synthesis of 1-allyl-[4,4-bipyridine]-1-ium

(119) ##STR00060##

(120) In a three necked flask, 4,4-bipyridyl (3.2 g, 20 mmol) was dissolved in 100 ml of distilled dichloromethane under vigorous stirring. Solution of allyl bromide (2 ml, 24 mmol) in 40 ml of dichloromethane was then added drop wise. After stirring overnight at 50 C., the solution was filtered yielded light yellow solid and yellow solution. The solid was washed with dichloromethane resulting 1,1-diallyl-[4,4-bipyridine]-1,1-diium. The solvent from organic layer was cut off under reduced pressure resulting yellow solid. The crude product was then recrystallized in dichloromethane:hexane (1:20) resulting yellow powder. Finally, the purified product was dried under vacuum.

(121) Yield: 70% (1.94 g)

2.SUP.nd .Step: 1-allyl-1-chloroacetyl-[4,4-bipyridine]-1,1-diium

(122) ##STR00061##

(123) In a three necked flask, 1-ally-4-(4-pyridyl)pyridinium bromide (2.77 g, 10 mmol) was dissolved in 100 ml of distilled dichloromethane under vigorous stirring at 0 C. Solution of chloroacetylchloride (1.5 ml, 20 mmol) in 40 ml of dichloromethane was then added drop wise. After stirring 1 h, the solution was filtered yielded light yellow solid. The solid was then washed with dichloromethane and dried under vacuum.

(124) Yield: 97% (3.77 g)

3.SUP.rd .Step: Synthesis of 1-allyl-1-=2-(1-ferrocenylmethyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium

(125) ##STR00062##

(126) 1-allyl-1-chloroacetyl-[4,4-bipyridine]-1,1-diium (1.12 g, 3 mmol) was added into a dichloromethane solution (100 ml) containing N-ferrocenylmethylimidazole (0.96 g, 3.6 mmol). The mixture was then refluxed overnight. Black solid was filtered and the solvent was evaporated under reduced pressure. The residue was washed in hexane resulting viscous brown oil.

(127) Yield: 60% (1.16 g)

3.3. Synthesis of 1-allyl-1-((N,N-dimethyl-N-ferrocenylmethylammonium)acetyl)-[4,4-bipyridine]-1,1-diium

(128) ##STR00063##

(129) 1-allyl-1-chloroacetyl-[4,4-bipyridine]-1,1-diium (1.12 g, 3 mmol) was added into a dichloromethane solution (100 ml) containing N,N-dimethyl-N-ferrocenylmethylammonium (0.87 g, 3.6 mmol). The mixture was then refluxed overnight. Black solid was filtered and the solvent was evaporated under reduced pressure. The residue was washed in hexane resulting yellow solid.

(130) Yield: 86% (1.63 g)

3.4. Synthesis of 1-heptyl-1-(2-(1-vinyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium

(131) ##STR00064##

(132) 1-heptyl-1-chloroacetyl-[44-bipyridine]-1,1-diium (1.35 g, 3 mmol) was added into a dichloromethane solution (100 ml) containing N-vinylimidazole (0.34 g, 3.6 mmol). The mixture was then refluxed overnight. The solvent was eliminated under reduced pressure. The residue was dissolved in water (50 ml) containing bis(trifluoromethane)sulfonimide lithium salt (1.05 g, 3.7 mmol). The solution was heated at 70 C. for 4 hrs resulting phase separation. The aqueous phase was eliminated and the organic phase was washed with water (3 times50 ml) then dried over MgSO.sub.4. Finally the organic layer was filtered and dried under vacuum.

(133) Yield: 46% (1.73 g)

3.5. Synthesis of 1-allyl-1-(2-(1-vinyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium

(134) ##STR00065##

(135) 1-allyl-1-chloroacetyl-[4,4-bipyridine]-1,1-diium (1.12 g, 3 mmol) was added into a dichloromethane solution (100 ml) containing N-vinylimidazole (0.34 g, 3.6 mmol). The mixture was then refluxed overnight. The solvent was eliminated under reduced pressure. The residue was dissolved in water (50 ml) containing bis(trifluoromethane)sulfonimide lithium salt (1.05 g, 3.7 mmol). The solution was heated at 70 C. for 4 hrs resulting phase separation. The aqueous phase was eliminated and the organic phase was washed with water (3 times50 ml) then dried over MgSO.sub.4. Finally the organic layer was filtered and dried under vacuum.

(136) Yield: 46% (1.75 g)

Example 4. Other Ionic Liquids or Polymeric Ionic Liquids of the Invention

4.1 Synthesis of N-allyl-N,N-dimethyl-N-ferrocenylammonium

(137) ##STR00066##

(138) The N,N-dimethyl-N-ferrocenylmethylprop-2-en-1-ammonium bromide was produced using the following procedure. First, the (dimethylaminomethyl)ferrocene (2.43 g, 10 mmol) and allyl bromide (2.42 g, 20 mmol) were dissolved in CH.sub.2Cl.sub.2 and the mixture was heated overnight at 55 C. Then the mixture was cooled down to room temperature and the solvent with unreacted allyl bromide were evaporated under reduced pressure. Finally, the residue was recrystallized using CH.sub.2Cl.sub.2/hexane (1:20 v/v) resulting orange powder. The purified product was filtered and dried under vacuum 1 day before use.

(139) Yield: 96% (3.5 g)

4.2. Synthesis of N-cobaltoceniumacetyl-N-ferrocenylmethyl-N,N-dimethylammonium

1.SUP.st .Step: Synthesis of 1-Chloroacetylcobaltocenium bis(trifluoromethane)sulfonamide

(140) ##STR00067##

(141) A solution of cobaltocene (1.89 g, 10 mmol) is distilled CH.sub.2Cl.sub.2 (40 ml) was added into a CH.sub.2Cl.sub.2 (80 ml) solution containing chloroacetyl chloride (1.36 g, 12 mmol) and aluminium (III) chloride (1.6 g, 12 mmol) at 0 C. under rigorous stirring. After 2 hrs of reaction, the mixture was then poured into water (100 ml). The aqueous phase was washed with CH.sub.2Cl.sub.2 (100 ml). Then LiTFSI (3.44 g, 12 mmol) was added into the aqueous layer. The solution was slightly heated (50 C.) under vigorous stirring for 2 hrs. After 2 hours of reaction, the reaction mixture was cooled down to room temperature resulting yellow crystals. By washing with water, the solid was dried under vacuum. The residue was applied to silica gel chromatography (methanol:dichloromethane=1:10) to afford yellow compound.

(142) Yield: 41% (2.23 g)

2.SUP.nd .Step: Synthesis of N-cobaltoceniumacetyl-N-ferrocenylmethyl-N,N-dimethylammonium

(143) ##STR00068##

(144) 1-Chlorocetylcobaltocenium bis(trifluoromethane)sulfonamide (0.55 g, 1 mmol) was added into a CH.sub.2Cl.sub.2 solution containing N-ferrocenylmethyl-N,N-dimethylamine (0.28 g, 1.2 mmol). The mixture was heated under vigorous stirring for overnight. The solvent was then eliminated under reduced pressure. The residue was then applied to silica gel chromatography (methanol:hexane=1:10) and concentrated affording viscous brown oil.

(145) Yield: 82% (0.64 g)

4.3. Synthesis of N-cobaltoceniumacetyl-N-vinylimdazolium

(146) ##STR00069##

(147) 1-Chloroacetylcobaltocenium bis(trifluoromethane)sulfonamide (0.55 g, 1 mmol) was refluxed with vinylimidazole (0.11 g, 1.2 mmol) in 100 ml of CH.sub.2Cl.sub.2 for 24 hrs. After the reaction, the mixture was poured into water. The underlayer was taken out and washed with water (3 times, 50 ml). The organic layer was dried over MgSO4 and concentrated to afford viscous brown oil

(148) Yield: 61% (0.39 g)

Example 5: Functionalization of Glassy Carbon Electrode by Using SI-ATRP: Surface-Initiated Atom Transfer Radical Polymerization

5.1. Electrografting of Initiator Layer

(149) Electrografting was performed by sweeping the potential from 0.5 V to 1.6 V versus saturated calomel electrode (SCE) at 0.1 V/s (cyclic voltammetry) in an aqueous solution containing 5 mM of 2-bromoethylamine and 0.1M LiClO.sub.4.

(150) The choice of electro-grafting is crucial for a covalent attachment of initiator layer onto the electrode surface. A various types of electrodes (current collectors) can be used, such as nano-carbon (carbon nanotubes or graphene), nickel, gold, platinum, etc. By using this method, the stability of the polymer brushes attached on the surface can be improved.

5.2. Polymerization at the Surface of Initiator-Modified Electrodes

5.2.1 Poly(N-ferrocenemethyl-N-allylimidazolium Bromide)

(151) An amount of 3.5 mM of the monomer N-ferrocenylmethyl-N-allylimidazolium bromide in MeCN was added to a dried beaker together with 4 M of the catalyst (CuCl), 1.4 M of deactivator (CuCl.sub.2) and 1.2 M of complexing agent (N,N,N,N,N-pentamethyldiethylenetriamine (PMDETA)). The solution was deoxygenated for 20 minutes. The initiator-modified electrodes were immersed into the reaction mixture for 2 hrs at 50 C. under argon flow.

(152) After 2 hrs of reaction, the electrodes were extracted from the reaction medium and thoroughly rinsed and sonicated in MeCN for 10 minutes. Then the modified electrodes were suffered 10 cycles of cyclic voltammetry in 0.1 M of tetrabutylammonium perchlorate (from 0 V to 0.8 V vs SCE) in order to eliminate the monomer weakly adsorbed at the surface.

(153) ##STR00070##

5.2.2. Polymer in Bloc: Poly(N-ferrocenemethyl-N-(methacryloyloxy Ethyl) Imidazolium and poly(N-vinyl-N-anthroquinoneimidazolium)

(154) The first layer was performed by using SI-ATRP with Poly(FcILs) or Poly(VAQILs) followed by a second SI-ATRP using Poly(VAQILs) or Poly(FcILs) under the same conditions described in the previous part.

(155) ##STR00071##

5.2.3. Poly(N-(3-anthroquinoneferrocenyl-1-methyl)-N-allylimidazolium Bromide)

(156) The in situ preparation of the monomer solution N-(3-anthraquinoneferrocenyl-1-methyl)-N-allylimidazolium bromide was described previously (c.f 4). Then the others products for the polymerization were added to obtain a final solution containing 0.1 mM of CuCl, 28 M of CuCl.sub.2, 0.05 mM of PMDETA. The reaction mixture was deoxygenated for 20 minutes. The surface-initiated electrodes were immersed into the mixture for 2 hrs. at 50 C. under argon flow.

(157) After 2 hrs of reaction, the electrodes were extracted from the reaction medium and thoroughly rinsed and sonicated in MeCN for 10 minutes. Then the modified electrodes were suffered 10 cycles of cyclic voltammetry in 0.1 M of tetrabutylammonium perchlorate (from 1.2 V to 0.8 V vs SCE) in order to eliminate the monomer weakly adsorbed at the surface.

(158) ##STR00072##

Example 6: Electrochemical Characterization of Imidazolium Based Molecules and of Imidazolium Based Polymeric Ionic Liquids of the Invention

6.1. Electrochemical Characterization of the Ionic Liquid N-cobaltoceniumacetyl-N-vinylimidazolium in Solution

(159) ##STR00073##

(160) The above ionic liquid containing a cobaltocene moiety was polymerized using SI-ATRP on a glassy carbon electrode. CV measurements are shown in FIG. 17.

6.2. Electrochemical Characterization of Poly(N-cobaltoceniumacetyl-N-vinylimdazolium) Immobilized on a Glassy Carbon Electrode

(161) A glassy carbon electrode was modified by immobilizing a polymeric ionic liquid on its surface using SI-ATRP with the monomeric cobaltocene-containing ionic liquid depicted below.

(162) ##STR00074##

(163) CV measurements are shown in FIG. 18.

6.3. Electrochemical Characterization of Poly(1-allyl-1-2-(1-ferrocenylmethyl-1H-imidazol-3-ium-3-yl)acetyl)-[4,4-bipyridine]-1,1-diium) Immobilized on a Glassy Carbon Electrode

(164) A glassy carbon electrode was modified by immobilizing a polymeric ionic liquid on its surface using SI-ATRP with the monomeric viologen-containing ionic liquid depicted below.

(165) ##STR00075##

(166) CV measurements are shown in FIG. 19.

Example 7: Influence of the Medium on the Electrochemical Properties of an Imidazolium Based Molecule and Imidazolium Based Polymeric Ionic Liquid of the Invention

(167) Structure of ionic liquid used for the electrochemical tests (First 5 lines of Table 1). The concentration of electro-active ionic liquid is fixed at 1 mM for the entire test.

(168) ##STR00076## Structure of the modified electrode with polymer brushes (last six lines of Table 1).

(169) ##STR00077##

(170) The results are presented in Table 1 below.

(171) TABLE-US-00001 TABLE 1 Comparison of electrochemical properties of electro-active ionic liquid in different medium (GCE = glassy carbon electrode). Exper- Relative iment E.sub.(Fc)- Capaci- number E.sub.(Fc) E.sub.(AQ) I.sub.a(Fc)/ E.sub.(AQ) tance # Medium (V) (V) I.sub.a(AQ) (V) C.sub.mod/C.sub.nue Electroactive 1 EMITFSI 0.457 0.434 2.1 0.891 Ionic 2 0.1M 0.559 0.735 1.2 1.294 liquid in EMITFSI/ACN solution 3 0.1M 0.463 0.120 1.3 0.344 HTFSI/ACN 4 0.1M 0.422 0.583 0.6 1.005 ElmHTFSI/H.sub.2O 5 0.1M 0.469 0.750 1.04 1.219 LiClO.sub.4/ACN Grafted 6 EMITFSI 0.473 0.590 2 1.064 9.6 Electroactive 7 0.1M 0.318 0.204 1.0 0.521 30.9 Ionic HTFSI/H.sub.2O liquid 8 0.1M 0.437 0.036 1.7 0.401 15.8 Polymer on HTFSI/ACN GCE 9 0.1M 0.485 0.587 0.7 1.071 9 surface ElmHTFSI/H.sub.2O 10 0.1M 0.485 0.586 1.4 1.063 14.1 EMITFSI/ACN 11 0.1M 0.442 0.910 1.2 1.352 12.1 LiClO.sub.4/ACN

CONCLUSIONS

(172) From the anodic current I.sub.a, the ratio I.sub.a(Fc)/I.sub.a(AQ) (see column 6 of Table 1) gives the information on the electrochemical response of ferrocene (Fc) and anthraquinone (AQ) of polymer brushes. The variation of this value may be due to the presence of imidazolium ring. A low value of this ration indicates that the electrochemical response of ferrocene is hindered. Otherwise, a high value indicates that the presence of imidazolium ring and ferrocene group modifies the solvation of anthraquinone part, following by a decrease of anthraquinone signal. In conclusion, from this ratio, we can obtain some information about the kinetic of the charge transfer and the influence of the chemical environment nearby the molecule for each solvent. The gap between the formal potential of ferrocene and anthraquinone E.sup.o.sub.(Fc)-E.sup.o.sub.(AQ) (see column 7 of Table 1) indicates the influence of chemical environment (solvent) on the thermodynamical properties of the studied systems. For the immobilized electro active ionic liquid polymers containing together ferrocene and anthraquinone, this gap gives a magnitude of the voltage obtained for an organic batteries based on these active materials. Relative capacitance is a measurement of capacity for immobilized ionic liquids polymers to stock energy via electrochemical double layer (properties of super capacitors). This relative capacitance (see column 8 of Table 1), measured in the potential window in which no redox process can be occurred (potential range in between E.sup.o.sub.(Fc) and E.sup.o.sub.(AQ)), is equal to the ratio between the capacitive current (non-faradic) in presence of immobilized ionic liquid polymers and the capacitive current in absence of immobilized ionic liquid polymers (Bare electrode). (Last 6 lines of Table 1).

(173) FIG. 12 shows the UV-Visible spectrum of the solution containing 1 mM of N-Ferrocenylmethyl-N-ethyleneamidoanthraquinone-imidazolium TFSI and 0.1 M of HTFSI in distilled water before (dash line) and after (solid line) electrolysis.

(174) Interdigitated electrodes (as depicted for instance in FIG. 14) can be fabricated with classical technologies as serigraphy, lithography and the printing could be performed on rigid or flexible substrates. Various electrode materials can be used (carbon, nickel, gold, . . . ) depending on the application and the chosen elaboration technique.

(175) As the nature of active materials (electroactive ionic liquid polymer) is identical on positive electrode and negative electrode, the grafting on both electrodes can be performed simultaneously. For the electrografting process, these 2 electrodes can be directly connected in order to get a unique working electrode for the electrografting of initiator layer (c.f 5.1). Then SI-ATRP can be performed.

(176) A material which can insure the ionic conduction between positive electrode and negative electrode can be physically deposited on both electrodes. There are multiple choices on the chemical nature of the ionic conducting material: electrolytic solution (solvent+ions), ionic gels, Ionic liquids, and ionic liquids polymers. Encapsulation of the whole system allows us to get an isolated device.

Example 8. Electrochemical Characterization of Quaternary Ammonium-Based Molecules and of Quaternary Ammonium-Based Polymeric Ionic Liquids of the Invention

8.1. Electrochemical Characterization of the Ionic Liquid N-allyl-N,N-dimethyl-N-ferrocenylammonium in Solution

(177) ##STR00078##

(178) The quaternary ammonium bromide bearing ferrocene and vinyl group was synthesized following the reaction scheme presented previously. The electrochemical behavior of the synthesized molecule was studied by cyclic voltammetry. FIG. 20 exhibits a reversible signal at 0.22 V vs Fc.sup.+/Fc corresponding to ferrocenyl ammonium redox couple. Besides that, the investigation of the evolution of the redox signal as function of the scan rate shows linear relation between the peak current and v.sup.1/2, suggesting that the system is under diffusion control. This linearity leads to determine the diffusion coefficient of the redox molecule using the Randles-Sevik equation and a value of 7.6510.sup.6 cm.sup.2/s was determined. This value is two times lower than that observed for ferrocene indicating that the diffusion of the ferrocenyl ammonium cation is slower than that of neutral ferrocene. Thus, having a positive charge linked to Fc provokes electrostatic interactions with other ions present in the electrolytic solution, resulting in lower diffusion coefficient.

(179) For undiluted ionic liquid the estimated concentration is around 2.8 M and the recorded CV (see FIG. 20) shows a weak oxidation and reduction peaks with large peak potential separation due to a large solution resistance (IR ohmic drop) and the high viscosity. However, after addition of small amount of acetonitrile the electrochemical response exhibits more defined oxidation and reduction peaks and the redox signal is well defined at a concentration of 0.56 M. This experiment evidences the possibility to record the electrochemical signal of ferrocene based ammonium ionic liquid at high concentration 1.1 and 0.56 M.

8.2. Electrochemical Characterization of Poly(N-allyl-N,N-dimethyl-N-ferrocenylammonium) Immobilized in a Glassy Carbon Electrode

(180) The previously synthesized quaternary ammonium-based molecules bear vinyl group that could be engaged for polymerization. The SI-ATRP process is based on the immobilization of thin initiator layer, which could be performed using the oxidative grafting of primary amine yielding to a bromide terminated layer. Following that, the modified electrode with the initiator layer was immersed in solution containing the redox ionic liquid monomer and all the necessary reagents, for the SI-ATRP, were added.

(181) Scheme illustrating the SI-ATRP procedure:

(182) ##STR00079##

(183) After the SI-ATRP process, the electrode was rinsed, sonicated and then electrochemically characterized. FIG. 21 displays the electrochemical response of the poly(ferrocenyl) based quaternary ammonium, Poly(FcIL), deposited onto GC electrode in acetonitrile electrolytic solution. The curve shows the presence of a well-defined reversible redox system at 0.45 V vs SCE attributed to the redox couple Fc.sup.+/Fc within the polymer backbone. This electrochemical signal confirms the success of the SI-ATRP polymerization using Fc quaternary ammonium monomer. Furthermore, the electrochemical responses of the polymer was performed at different scan rates. This investigation clearly show a linear variation of the peak current versus the scan rate suggesting the presence of non-diffusive process. Besides that, for higher scan rate (above 1 V/s) the redox signal of ferrocene starts to deviate from fully reversible system indicating that the system is limited by the electron transfer rate. The linear dependency of the Ep vs Log(v) leads to determine the apparent electron transfer rate constant which is found to be around 120 s.sup.1 highlighting the presence of fast electron transfer of the attached ferrocenyl groups. Several parameters could explain the fast electron transfer rate including the structure of the polymer in the form of brushes, the short distance of the initiator and the composition of the polymer which includes a positive and negative charges. Indeed, the presence of ions within the film may enhance the electron hopping process and consequently the electron transfer rate.

(184) Poly(ionic liquids) refer to a subclass of polyelectrolytes that contain an ionic liquid (IL) species in each monomer repeating unit, connected through a polymeric backbone to form a macromolecular structure. They are considered as interesting materials for electrochemical applications (batteries, supercapacitor, and solid electrolyte) thanks to the presence of ionic species inside the structure. Having these characteristics, the electrochemical responses of the generated polymer was performed in acetonitrile solution in the absence of supporting electrolyte (FIG. 21c). The curve shows clearly the presence of oxidation and reduction waves corresponding to the Fc.sup.+/Fc redox couple despite the absence of supporting electrolyte. Compared to the CV in FIG. 21a the peaks currents are slightly lowered and the peaks potentials are shifted to more positive potential. This result suggests that the generated polymer brushes act as self-supporting electrolyte thanks to the presence of cation and the anion within the film and that the oxidation/reduction of the Fc units is not limited by the rate of counter-ion migration into/out of the polymer.

(185) The modulation of the properties of interfaces such as the variation of the wettability is of high interest. The best advantage of using electrochemistry as an external stimulus is its ability to switch the surface oxidation state in a few second or less. FIG. 22 shows the contact angle (=CA) for the polymer attached onto ITO (indium tin oxide) substrate before and after electrochemical oxidation. Interestingly, after electrochemical oxidation the CA decreases suggesting the presence of hydrophilic surface. Besides the electrochemical modulation of the CA, the latter could be also tuned by anion exchange. Both processes for contact angle variation are fully reversible. The combination of the electrochemical and anion exchange leads to drive the transition between hydrophobicity and hydrophilicity of the surfaces.

8.3. Electrochemical Characterization of the Ionic Liquid 1-allyll-1-((N,N-dimethyl-N-ferrocenylmethylammonium)acetyl)-[4,4-bipyridine]-1,1-diium in Solution

(186) ##STR00080##

(187) The results obtained are shown in FIG. 23.

Example 9. Further Examples of the Ionic Liquids of the Invention

(188) Chemical

(189) All the starting compounds were commercially purchased from Aldrich and used as received. LiTFSI, ferrocenylmethyl-trimethylammonium iodide, bromoethane, 4-methoxyphenol, tetrabutylammonium tetrafluoroborate (Bu4NBF4) were purchased from Alfa. Solvent such as N,N-dimethylformamide, acetonitrile, ethanol, dichloromethane, THF, ethanol, ethylacetate, diethylether, DMF were purchased from Aldrich. Ultrapure water (Millipore, resistivity 18.2 M.Math.cm) was obtained in the laboratory.

(190) Apparatus

(191) 1H-NMR (400 MHz) and 19F-NMR (125.75 MHz) spectra have been recorded on a BRUKER AVANCE DRX 400 spectrometer.

(192) Chemical shifts (d) are expressed in ppm related to the tetramethylsilane (TMS) signal. Coupling constants are expressed in Hz. 1H-NMR assignments are given as follows: d (multiplicity, coupling constant, number of protons involved, assignment).

(193) Electrochemical Measurements

(194) For the electrochemical experiments, a conventional three-electrode cell was used. Platinum wire was used as auxiliary electrode. Saturated calomel electrode, SCE, was used as reference electrode. Glassy carbon electrode GCE (3 mm diameter) was used as working electrode. Prior to use the working electrodes were polished using successively SiC-paper 5 m (Struers) and DP-Nap paper 1 m (Struers) with Al2O3 0.3 m slurry (Struers). After polishing the electrode was thoroughly rinsed with ultrapure water (18.2 M cm). Before any electrochemical measurements the solutions were deoxygenated by bubbling argon gas for 15 minutes. During the experiment the electrochemical cell remains under argon. The potentiostat used in this study was CHI 660C (CH Instruments, made in TX, USA).

(195) General Protocol of Ion Exchange

(196) The imidazolium derivative (1 equiv., 50 mmol) and the inorganic salt source of the cationic species (1.2 equiv., 60 mmol) dissolved in 20 ml of deionized water were mixed together in a round-bottom flask. Then, the reaction was stirred overnight at the indicated temperature. After return to room temperature, the two phases were separated. The ionic liquid is in the organic phase which was washed with water thrice, then mixed with dichloromethane and charcoal. This suspension was purified through aluminium oxide layer (3 cm thickness), then dried over magnesium sulphate. The solvent was removed by rotavapor and trace of water was taken off by vacuum pump overnight.

9.1. Nitrophenyl-imidazolium Based Ionic Liquid

N-(4-nitrophenylethyl)imidazole

(197) Under argon, imidazole (26.08 mmol, 1.2 equiv., 1.77 g) was added to 100 ml of distilled THF. Sodium hydride 60% in oil (27.16 mmol, 1.25 equiv., 1.09 g) was then introduced to the solution. The reaction mixture was stirred for 1.5 hrs at room temperature. The solution of 1-(2-Bromoethyl)-4-nitrobenzene (27.73 mmol, 1 equiv., 5.0 g) in distilled THF (50 ml) was then added to the flask which was then heated at 50 C. Two phases had appeared after 5 hrs of reaction, and the heating was continued during 31 hr more. After return to room temperature, the reaction solution was hydrolyzed by 10 mL of distilled water. The solvent was removed and the crude product was dissolved in dichloromethane. The organic phase was washed with distilled water (100 mL3 times) then dried over magnesium sulfate. The solvent was then evaporated. Intermediate 1 is obtained as a Yellow-brown crystalline powder in 83% yield (3.94 g).

(198) .sup.1H NMR (DMSO): 3.17 (t, 7.0 Hz, 2H, CH.sub.2Ar), 4.26 (t, 7.0 Hz, 2H, CH.sub.2N), 6.83 (s, 1H, NCH), 7.15 (s, 1H, NCH), 7.43 (d, 8.8 Hz, 2H, C.sub.ArH.sub.metaNO2), 7.49 (s, 1H, NCHN), 8.14 (d, 8.8 Hz, 2H, C.sub.ArH.sub.orthoNO2).

N-(4-nitrophenylethyl)-N-(2-aminoethyl)imidazolium Bromide

(199) ##STR00081##

(200) A two-neck flask containing dry ethanol (30 ml) was added N-(4-nitrophenylethyl) imidazole (18.2 mmol, 1 equiv., 3.94 g) under argon atmosphere. The mixture was stirred for 15 minutes then was added 2-bromoethylamine hydrobromide (18.2 mmol, 1 equiv., 3.72 g). After 24 hrs of reflux at 50 C. and return to room temperature, ethanol was evaporated to form crude ionic liquid in viscous oil. The crude ionic liquid was washed with ethylacetate (20 ml5 times), then was dried under vacuum at 50 C. The purity of ionic liquid was checked by thin layer chromatography using dry ethanol. This ionic liquid is soluble in water and ethanol. The title compound is obtained as a viscous orange liquid in 61% yield (1.2 g).

(201) .sup.1H NMR (DMSO): 3.27 (m, 4H, CH.sub.2Ar and NH.sub.2CH.sub.2CH.sub.2N), 3.66 (t, 6.0 Hz, 2H, CH.sub.2NH.sub.2), 4.44 (t, 7.2 Hz, 2H, ArCH.sub.2CH.sub.2N), 7.36 (d, 1.2, 1H, NCH), 7.49 (d, 8.8 Hz, 2H, C.sub.ArH.sub.metaNO2), 7.55 (d, 1.6 Hz, 1H, NCH), 8.17 (d, 8.8 Hz, 2H, C.sub.ArH.sub.orthoNO2), 8.49 (s, 1H, NCHN).

Example 10. Monolayer of Nitrophenyl Containing Ionic Liquid of the Invention

10.1. Experimental Section

(202) Tetrabutylammonium tetrafluoroborate (Bu.sub.4NBF.sub.4) and tetrabutylammonium bromide purchased from Aldrich (electrochemical analysis grade 99%) were used as supporting electrolyte at a concentration 0.1 M for each. Dry acetonitrile (ACN) was purchased from Fulka and stored over molecular sieves. 2-(4-aminophenyl)acetic acid, perchloric acid (HClO.sub.4), sodium nitrite (NaNO.sub.2), ferrocene and dopamine redox probes were purchased from Sigma-Aldrich. The electroactive ionic liquid, 1-ferrocenylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([FcEMIM][TFSI]), and N-(2-aminoethyl)-N-(4-nitrophenylethylimidazolium) bromide were synthesized following the process described in example 3.

(203) For the electrochemical experiments, a conventional three-electrode cell was used. Platinum wire was used as auxiliary electrode, saturated calomel electrode SCE as reference electrode. Glassy carbon electrode GCE (3 mm diameter) and microelectrode carbon fiber (7 m diameter) were used as working electrodes. Prior to use the working electrodes were polished using decreasing size of diamond pastes. The potentiostat used in this study was CHI 660C (CH Instruments, made in USA).

10.2. Results and Discussion

10.2.1. Redox Properties of Nitrophenyl-Imidazolium Based Ionic Liquid Modified Electrode, Immobilization of Nitrophenyl-Imidazolium Based Ionic Liquid

(204) In this example, surface modification with an imidazolium based-ionic liquid bearing redox functionality onto carbon electrodes has been investigated. The electrochemical oxidation of N-(2-aminoethyl)-N-(4-nitrophenylethylimidazolium) bromide onto glassy carbon electrode conduces to the immobilization of nitrophenyl-imidazolium layers. The presence of this layer was evidenced by electrochemical characterization that thanks to the presence of the redox active nitrophenyl moieties. Furthermore, the modified electrode was then characterized by electrochemical methods in the presence of various redox probes, from which it was concluded that the generated layer was very thin and/or less dense layer probably due to the specific arrangement of the positively charged imidazolium.

(205) The immobilization of the nitrophenyl containing ionic liquid of the invention onto the carbon electrode was obtained by the electrochemical grafting through the oxidation of the primary amine based on an ionic liquid derivative (see Scheme 4.1.). The voltammetry of GC electrode, in CAN (acetonitrile) solution containing 610.sup.3 M N-(2-aminoethyl)-N-(4-nitrophenylethylimidazolium) bromide and 0.1 M NBu.sub.4Br, exhibits an irreversible oxidation wave at a potential around 1.2 V vs SCE (see FIG. 15). This anodic peak corresponds to the oxidation of the amine group leading to the formation of the corresponding radical. During the oxidation process, aminyl radicals were generated in the vicinity of the electrode and react rapidly with the electrode surface. The peak current becomes smaller after few cycles suggesting the formation of thin film attached onto the electrode surface. In this example, the grafting was realized by performing five cycles of CV (Cyclic Voltammetry).

(206) ##STR00082##

10.2.2. Electrochemical Response of Modified Electrode

(207) After the oxidative grafting process, the electrode was rinsed and sonicated in acetonitrile solution and transferred to acidic solution. The CV recorded on modified carbon electrode in the de-aerated electrolytic solution is shown in FIG. 16.

(208) The data show the presence of an irreversible reduction wave, at potential E.sub.p=0.43 V vs SCE, very close to that of the reduction wave in nitrobenzene solution. The presence of this signal indicates that nitrophenyl (NP) groups are immobilized onto the electrode surface. During the reverse scan an anodic wave at E.sub.p=0.25 V vs CE is observed. Upon the second scan the first irreversible reduction wave disappears and new reversible system appears with standard redox potential E.sup.o=0.24 V vs SCE. The potential peak separation of this system is around 20 mV indicating the presence of immobilized system onto the electrode surface. This reversible system has been attributed to the redox couple NHOH/NO. The presence of this system and the drastic decrease of the reduction wave during the second scan indicate that the grafted NO.sub.2 groups are totally reduced (see Scheme 4.2.). The presence of the electrochemical signal of NP suggests the occurrence of the grafting of nitrophenyl-imidazolium moieties onto the carbon electrode.

(209) The analysis of the electrochemical signal on FIG. 16 could provide estimation of the amount of the attached NP groups. The charge of the electroactive species could be measured and the surface concentration is calculated using the formula =Q/nFA, where Q corresponds to the charge measured by integration of the two electrochemical signals, reduction wave at 0.43 and oxidation wave at 0.24 V vs SCE, n is the number of the electron, F is the faraday constant, and A represent the area of the electrode. As the reduction of NP groups in acidic media could exchange 4 or 6 electrons, corresponding to the formation of NHOH or NH.sub.2, respectively, the surface concentration .sub.NP was calculated by taking into account these two processes using the following equation:
.sub.NP=Q.sub.(NO2.fwdarw.NH2)/6FA+Q.sub.(NO2.fwdarw.NHOH)/4FA

(210) Here, the average surface concentration of attached NP groups was found to be around 1.210.sup.10 mol.Math.cm.sup.2. This value appears to be very close to the value reported in the literature, (from 1.4 to 6.410.sup.1 mol.Math.cm.sup.2) or (510.sup.10 mol.Math.cm.sup.2) that suggests the formation of a dense monolayer onto the electrode surface.

(211) ##STR00083##