CO-POLYMERS

Abstract

Co-polymers formed from at least one monomer of formula (A) and at least one monomer of formula (B): (A) (B) wherein R.sup.1, R.sup.2, R.sup.3 and L are as defined herein; may be dispersed or dissolved in an organic solvent which optionally contains carbon nanostructures. A substrate coated or printed with the dispersion or solution may be used in an electrochromic device.

Claims

1. A copolymer formed from at least one monomer of formula (A) and at least one monomer of formula (B) ##STR00007## where R.sup.1 is a polyaromatic or polyheteroaromatic ring or molecular graphenes of less than 22.000 g/mol; L is a C.sub.1-6 alkylene, C.sub.2-5 alkenylene or C.sub.2-6 alkynylene linker wherein one or two carbon atoms are optionally replaced with O, S or NH; each of R.sup.2 to R.sup.3 are independently selected from the group consisting of: C.sub.6-14 alkyl, which may optionally comprise a C.sub.3-7 cycloalkyl, C.sub.6-10 aryl or C.sub.5-10 heteroaryl group and wherein a carbon atom of the alkyl chain is optionally replaced with O, S or NH; C.sub.3-7 cycloalkyl, C.sub.6-10 aryl or C.sub.5-10 heteroaryl; a polyalkylene glycol radical; or R.sup.2 and R.sup.3 together with the atoms to which they are attached may form a 5-10 membered heterocyclic ring, optionally containing a further heteroatom selected from O, S or NH; and the molar ratio of the monomer of formula (B) to the monomer of formula (A) is from 3:1 to 15:1.

2. A copolymer according to claim 1 wherein each of R.sup.2 to R.sup.3 are independently selected from the group consisting of: C.sub.6-14 alkyl, which may optionally comprise a C.sub.3-7 cycloalkyl, C.sub.6-10 aryl or C.sub.5-10 heteroaryl group and wherein a carbon atom of the alkyl chain is optionally replaced with O, S or NH; C.sub.3-7 cycloalkyl, C.sub.6-10 aryl or C.sub.5-10 heteroaryl; or R.sup.2 and R.sup.3 together with the atoms to which they are attached may form a 5-10 membered heterocyclic ring, optionally containing a further heteroatom selected from O, S or NH.

3. A copolymer according to claim 1 wherein the ratio of monomer (B) to monomer (A) is from 8:1 to 12:1.

4. A copolymer according to claim 1 which is a polymer of general formula (I) ##STR00008## wherein L, R.sup.1, R.sup.2 and R.sup.3 are defined in claim 1 or claim 2 and wherein, within the polymer of general formula (I), R.sup.1 groups may have differing values, R.sup.2 groups may have differing values and R.sup.3 groups may have differing values; n is 3-15; and p is 3-140.

5. A copolymer according to claim 1 wherein R.sup.1 is a polyaromatic ring system selected from the group consisting of benzo[a]pyrene, anthracene, chrysene, pyrene, phenanthracene, naphthalene and tetracene or a polyheteroaromatic group selected from indole, quinoline, isoquinoline and polypyrroles,

6. A copolymer according to claim 5 wherein R.sup.1 is pyrene.

7. A copolymer according to claim 1 wherein L is a C.sub.1-4 alkylene linker, wherein one carbon atom is optionally replaced with O, S or NH.

8. A copolymer according to claim 7 wherein L is: CH.sub.2, CH.sub.2CH.sub.2, CH.sub.2O, OCH.sub.2, CH.sub.2CH.sub.2CH.sub.2, CH.sub.2OCH.sub.2 or CH.sub.2NHCH.sub.2.

9. A copolymer according to claim 1 wherein each of R.sup.2 and R.sup.3 is independently C.sub.8-12 alkyl and optionally comprises a C.sub.3-7 cycloalkyl ring.

10. A copolymer according to claim 1 wherein R.sup.2 and R.sup.3 are the same.

11. A copolymer according to claim 1 wherein the monomer of formula (A) is 2-((pyren-1-ylmethoxy)methyl)-2,3-dihydrothieno[3,4-b][1,4]dioxine; and/or the monomer of formula (B) is 3,4-bis((2-ethylhexyl)oxy)thiophene.

12. A process for the preparation of a polymer according to claim 1, the process comprising reacting a monomer of formula (A) as defined above with a monomer of formula (B) as defined above in the presence of an oxidising agent, wherein the molar ratio of the monomer of formula (B) to the monomer of formula (A) is from 3:1 to 15:1.

13. A process according to claim 12 wherein the oxidising agent comprises iron (III) chloride, which is present in excess.

14. A dispersion or solution comprising a copolymer according to claim 1 and an organic solvent.

15. A dispersion or solution according to claim 14 wherein the organic solvent is selected from the group consisting of include toluene, N,N-dimethylformamide (DMF), acetonitrile, tetrahydrofuran (THF), ethyl acetate, chloroform and mixtures thereof.

16. A dispersion or solution according to claim 15 wherein the organic solvent is a mixture of chloroform and toluene, preferably a mixture of toluene:chloroform in a volume ratio of 1:1 (v/v) to 1:10 (v/v).

17. A dispersion or solution according to claim 14 wherein the copolymer is present at a concentration of from 0.5 to 1.5 g/l.

18. A dispersion or solution according to claim 14 further comprising carbon nanostructures, wherein said carbon nanostructures are selected from the group consisting of carbon-based nanotubes, sheets, nanocones, nanohorns, nanoribbons, nanoplatelets, nanofibers, graphene, crystalline nanoparticles, nanodots, graphene quantum dots and amorphous nanoparticles.

19. A dispersion or solution according to claim 18, wherein said carbon nanostructures are metal-containing carbon nanostructures, which preferably contain a metal selected from the group consisting of iron, cobalt, nickel, copper, gold, silver, tin, palladium and platinum.

20. A dispersion or solution according to claim 18, wherein said carbon nanostructures are nanotubes, wherein said nanotubes are selected from single wall carbon nanotubes (SWCNTs) and multi wall carbon nanotubes (MWCNTs).

21. A dispersion or solution according to claim 20 wherein the carbon nanotubes are MWCNTs, especially pristine MWCNTs.

22. A dispersion or solution according to claim 18 which comprises 2-15 wt % carbon nanostructures, wherein weight percentages are given with respect to the polymer.

23. A substrate coated or printed with a coating or printing composition comprising a copolymer according to claim 1.

24. A coated or printed substrate according to claim 23 wherein the coating or printing composition is obtainable by providing a dispersion or solution comprising the copolymer and an organic solvent, and removing the solvent.

25. A coated or printed substrate according to claim 23, wherein, independently or in combination said substrate is one or more of: in form of a film or panel; optically transparent; formed from a fibrous material or is glass or a polymer selected from acrylic, polystyrene, polycarbonate, allyl diglycol, styrene acrylonitrile copolymer, poly(4-methyl 1-pentene), polyester, polyamide or polyethylene terephthalate (PET); flexible.

26. A coated or printed substrate according to claim 25 wherein the substrate is a PET substrate.

27. A coated or printed substrate according to claim 23 wherein the substrate further comprises an electrically conductive material.

28. A coated or printed substrate according to claim 27 wherein the substrate is indium doped tin oxide coated PET (PET-ITO).

29. A coated or printed substrate according to claim 23 wherein the substrate has a thickness of between 0.01 mm to 10 mm.

30. A coated or printed substrate according to claim 23 which comprises 2-12 layers of the coating composition.

31. A coated or printed substrate according to claim 23, wherein the total thickness of the combined layers of the coating as defined by Atomic Force Microscopy is suitably from 100-500 nm.

32. A method for preparing a coated or printed substrate comprising the steps of: i) Providing a dispersion or solution comprising a copolymer and an organic solvent, the copolymer being formed from at least one monomer of formula (A) and at least one monomer of formula (B) ##STR00009## where R.sup.1 is a polyaromatic or polyheteroaromatic ring or molecular graphenes of less than 22.000 g/mol; L is a C.sub.1-6 alkylene, C.sub.2-5 alkenylene or C.sub.2-6 alkynylene linker wherein one or two carbon atoms are optionally replaced with O, S or NH; each of R.sup.2 to R.sup.3 are independently selected from the group consisting of: C.sub.6-14 alkyl, which may optionally comprise a C.sub.3-7 cycloalkyl, C.sub.6-10 aryl or C.sub.5-10 heteroaryl group and wherein a carbon atom of the alkyl chain is optionally replaced with O, S or NH; C.sub.3-7 cycloalkyl, C.sub.6-10 aryl or C.sub.5-10 heteroaryl; a polyalkylene glycol radical; or R.sup.2 and R.sup.3 together with the atoms to which they are attached may form a 5-10 membered heterocyclic ring, optionally containing a further heteroatom selected from O, S or NH; and the molar ratio of the monomer of formula (B) to the monomer of formula (A) is from 3:1 to 15:1; ii) Applying the dispersion onto the substrate using a suitable coating or printing method; and iii) Removing the solvent.

33. A method according to claim 32 wherein the coating or printing method is spray coating.

34. An electrochromic device comprising a coated or printed substrate according to claim 23.

35. An electrochromic device according to claim 34 comprising electrodes and/or counter electrodes formed from the coated or printed substrate.

36. A product comprising an electrochromic device of the invention according to claim 35 wherein the product is selected from the group consisting of windows, displays, monitors, sun shades, mirrors, wearable objects, furniture, toys, labels, documents or packaging.

37. An electrochromic ink comprising a dispersion or solution according to claim 14.

Description

FIGURES

[0100] FIG. 1. a) Schematic representation of a traditional dual polymer transmission ECD (not to scale). b) Structure of copolymer 1.

[0101] FIG. 2. Schematic representation of the synthesis of the monomers 2 and 3 and the copolymer 1 FIG. 3. a) Schematic illustration of the preparation of the blending copolymer 1 and MWCNTs. b) Picture of the dispersion copolymer 1 and MWCNT (7.5%) in toluene/CHCl.sub.3 (1:5, v/v) after a week from the preparation. Homogeneity tests of the drop coated solution on PET with a mixture of copolymer 1 and MWCNT (7.5%) in c) pure CHCl.sub.3 and d) in toluene/CHCl.sub.3 (1:5, v/v).

[0102] FIG. 4. Schematic representation of the coating of the blend solution on PET surfaces, depending on the percentage of MWCNTs and on the number of layers coated on the surface

[0103] FIG. 5. SEM pictures of a) 7 layers of solution of copolymer 1 coated on PET and different layers of mixtures of copolymer 1+0.75 mg MWCNT: b) 7 layers and c) 1 layer.

[0104] a) FIG. 6. TEM analysis of the blends coated on the metallic grid. b) Table 1. XPS analysis of the elements C, O, S of 9 layers of the copolymer 1 and blends coated by spray on PET.

[0105] FIG. 7. Plot of the average of the thickness of the films depending on the number of layers. The average is calculated taking in account the values of the height at the maximum value of numbers of events in the TM-AFM measurements.

[0106] FIG. 8. First Cyclic Voltammetry of copolymer 1 in PET-ITO electrode in red, in black the copolymer 1 with 7.5% of MWCNT in PET-ITO electrodes. Scan rate was 20 mV/s vs. Ag/AgCl reference. At least 4 wave peaks are observed. The presence of CNT seems to influence mainly the oxidation occurring circa 1.5 V.

[0107] FIG. 9. (a) Schematic representation of a traditional dual polymer transmission ECD (not to scale). (b) Picture of the real assembled ECD, containing the copolymer 1 with the addition of 10% of MWCNTs.

[0108] FIG. 10. AA when different voltages are applied on the device a) without and b) with MWCNT (7.5% w).

[0109] FIG. 11. Switching cycles for assembled electrochromic devices.

[0110] FIG. 12. Cycling performances of assembled electrochromic devices (a) without MWCNTs and (b) with 7.5% of MWCNT in L*a*b color space. (c) Trend of the T during the ON-OFF process of the cycles after the first cycles and 16.000 cycles of the device without MWCNTs (brown and red line) and the device with the addition of 7.5% MWCNTs (black and grey line). (d) E versus the number of cycles depending on the percentage of MWCNT added during the formulation of the blend

[0111] FIG. 13. WCA measurements of a) copolymer 1 and b) mixture copolymer 1+0.75 mg MWCNTs coated on PET.

[0112] FIG. 14. Plot of the average roughness (Ra) and root mean square roughness (Rq) depending on the number of layers of the films of the solution of copolymer 1 with (0.75 mg, =7.5% w) and without the MWCNTs.

[0113] FIG. 15. Plot of the number of the events depending the height of the particles in the case of 1 layer of the blend is coated on the PET surfaces.

[0114] FIG. 16. Cyclic of 9 layers of blends on PET-ITO for different percentages of MWCNTs: a) 0%, b) 2.5%, c) 5.0% and d) 10.0%. Ag/AgCl was used as the reference electrode, a platinum wire as the counter electrode and the electrolytic solution was LiClO.sub.4 (0.1M) in propylene carbonate. The cyclic voltammetry measurements were performed with a scan rate of 20 mV/s from 1.5V to 2V during 6 cycles.

[0115] FIG. 17. Synthesis of the copolymer 4.

[0116] FIG. 18. Cyclic voltammetry measurements of 9 layers spray coated on PET-ITO of copolymer shown without the pyrene moiety and MWCNTs (7.5%). Ag/AgCl was used as the reference electrode, a platinum wire as the counter electrode and the electrolytic solution was LiClO.sub.4 (0.1M) in propylene carbonate. The CV measurements have been performed with a scan rate of 20 mV/s from 1.5V to 2V during 6 cycles.

Materials and Methods

[0117] Thin Layer Chromatography (TLC) was conducted on pre-coated aluminum sheets with 0.20 mm Machevery-Nagel Alugram SIL G/UV254 with a fluorescent indicator UV.sub.254. Column chromatography was carried out using Merck Gerduransilica gel 60 (particle size of 40-60 m).

[0118] Melting points (m.p.) were measured on a Bchi Melting Point B-545 in open capillary tubes and have not been corrected.

[0119] Infrared spectra (IR) were recorded on PerkinElmer Spectrum Two.

[0120] Nuclear magnetic resonance (NMR).sup.1H and .sup.13C spectra were obtained on a 400 MHz NMR (Jeol JNM EX-400) for experiment at room and high temperatures. Chemical shifts were reported in ppm according to tetramethylsilane using the solvent residual signal as an internal reference (CDCl.sub.3: .sub.H=7.26 ppm, .sub.C=77.16 ppm). Coupling constants (J) were given in Hz.

[0121] Resonance multiplicity was described as s (singlet), d (doublet), dd (doublet of doublets), m (multiplet) and broad (broad signal). Carbon spectra were acquired with a complete decoupling for the proton.

[0122] Mass spectrometry was performed by the Centre de spectromtrie de masse at the Universit de Mons in Belgium where they performed ESI-MS and MALDI-MS, on using the following instrumentation. ESI-MS measurements were performed on a Waters QToF2 mass spectrometer operating in positive mode. The analyte solutions were delivered to the ESI source by a Harvard Apparatus syringe pump keeping the reaction at a flow rate of 5 L/min. Typical ESI conditions were, capillary voltage 3.1 kV; cone voltage 20-50 V; source temperature 80 C.; desolvation temperature 120 C. Dry nitrogen was used as the ESI gas. For the recording of the single-stage ESI-MS spectra, the quadrupole (rf-only mode) was set to pass ions from 50 to 1000 Th, and all ions were transmitted into the pusher region of the time off-light analyser where they were mass analysed with 1 s integration time. MALDI-MS were recorded using a Waters QToF Premier mass spectrometer equipped with a nitrogen laser, operating at 337 nm with a maximum output of 500 mW delivered to the sample in 4 ns pulses at 20 Hz repeating rate. Time of-flight analyses were performed in the reflectron mode at a resolution of about 10,000. The matrix solution (1 l) was applied to a stainless steel target and air dried. Analyte samples were dissolved in a suitable solvent to obtain 1 mg/mL solutions. 1 l aliquots of those solutions were applied onto the target area already bearing the matrix crystals, and air dried. For the recording of the single-stage MS spectra, the quadrupole (rf-only mode) was set to pass ions from 100 to 1000 Th, and all ions were transmitted into the pusher region of the time-of-flight analyser where they were analysed with 1 s integration time

[0123] Scanning electron microscopy (SEM) images were obtained on a JEOL 7500F. The films at different percentage of MWCNTs and different number of layers, were spray-coated on PET, then a layer of 10 thick of metal Gold was coated by using a JEOL JFC-1300.

[0124] Transmission electron microscopy (TEM) images were obtained using the SEM microscope JEOL 7500F using the TEM mode. The blend was spray coated on the metal grid for TEM, CF200-Cu CARBON FILM on 200 Square Mesh Cupper Grid provided by Electron Microscopy Sciences.

[0125] Water contact angle (WCA) measurements were performed using a CA-A contact angle meter (Kyowa Scientific Company Ltd, Japan) at ambient temperature. Water droplets (0.2 mL) were dropped carefully onto the surface. The average WCA value was determined by measuring at three different positions of the same sample, and their images were captured with a traditional digital camera (Sony).

[0126] Profilometry of the layers coated on PET was investigated using a Surface Profile Measuring System Dektak 8 from Veeco Instruments.

[0127] X-ray photoelectron spectroscopy (XPS) characterization was performed with a SSX-100 system (Surface Science instrument). The photon source was a mono chromatized Al K line (hv=1486.6 eV) applied with a take-off angle of 35. In the spectrum analysis, the background signal was subtracted by Shirley's method. The C level peak position of carbon atoms was taken as the reference at 284.5 eV, when for O and S the reference was respectively at 533 eV and 162 eV. The spectrum analysis was carried out by fitting the peak shape obtained in the same analysing conditions and other components with mixed (Gaussian+Lorentzian) line shapes. XPS atomic ratios have been estimated from the experimentally determined area ratios of the relevant core lines, corrected for the corresponding theoretical atomic cross-sections and for a square root dependence of the photoelectrons kinetics energies.

[0128] Cyclic voltammetry (CV) measurements were performed in a conventional three-electrode cell. The blend deposited by spray-coating on a PET-ITO electrode was the working electrode, a platinum wire was used as the counter electrode, an Ag/AgCl electrode was the reference electrode, and the supporting electrolyte was a solution of propylene carbonate with lithium perchlorate salt (0.1 M).

[0129] UV-vis absorbance spectra and spectroelectrochemical measurements of the copolymer and copolymer/CNT devices were performed using an UV-vis spectrophotometer Cary 300 Bio (spectral range from 351 to 800 nm). On the spectroelectrochemical measurements the applied potential to the devices were controlled with a potentiostat Autolab PGSTAT 100N. The devices were placed in the spectrophotometer compartment perpendicularly to the light beam. The potentiostat applied a continuous electric potential (at selected values), and the spectrophotometer registered the absorbance spectra within the range of the equipment.

[0130] Cycling experiments were performed using a camera equipped by a diffuse lamp to control the luminosity (ML series Cold-Cathode Light Panel from Vision Light Tech), and a colour Checker (colour pattern). The electrochromic devices were placed inside the chamber and connected to a function generator. While the function generator applied a determined potential in a square waveform (changing from positive to negative), the camera was setup to record, from time to time, 150 pictures during a calculated period of time, enough to see a complete cycle of the device oxidation and reduction (during several hours, days, or weeks depending on the durability of the device). The pictures were then treated with Matlab software to convert the RGB coordinates obtained from the images into L*a*b* coordinates.

Chemicals

[0131] Chemicals were purchased from Sigma Aldrich, TCI and ABCR and were used as received. Solvents were purchased from Sigma Aldrich, and deuterated solvents from Eurisotop. Solvents for spectrophotometry was purchased from Acros Organics and Jansen Chemicals.

Synthetic Strategy

Synthesis of 3,4-bis((2-ethylhexyl)oxy)thiophene (DMT Monomer), 2

[0132] ##STR00005##

[0133] 3-4 dimethoxythiophene (1442 mg, 10.0 mmol), 2-ethylhexanol (5470 mg, 42.0 mmol) and p-toluene sulfonic acid (230.3 mg, 1.0 mmol) were dissolved in toluene (50 mL) under inert atmosphere and the mixture was stirred at 110 C. for 24 hours. The reaction was degassed each 3 hours to release methanol. The solution was cooled at room temperature, the organic phase was washed with water (325 mL) and dried over Na.sub.2SO.sub.4. The organic solvent was evaporated in vacuo and the crude was purified by silica gel column chromatography (eluent: benzene), affording 2 as pale yellow oil (92% yield, 3133 mg)..sup.[281]

[0134] M. f.: C.sub.20H.sub.36SO.sub.2. IR (NaCl disks): v (cm.sup.1)=3649, 2927, 2360, 1844, 1558. .sup.1H-NMR (400 MHz, CDCl.sub.3): (ppm) 0.92 (m, 12H), 1.19-1.65 (m, 16H), 1.76 (m, 2H), 3.85 (d, 4H, J=5.9 Hz), 6.17 (s, 2H). .sup.13C NMR (100 MHz, CDCl.sub.3): (ppm) 148, 96, 73, 39, 30, 29, 24, 23, 14, 11.

Synthesis of 2-((pyren-1-ylmethoxy)methyl)-2,3-dihydrothieno[3,4-b][1,4]dioxine (EDOT-Pyrene Monomer) 3

[0135] ##STR00006##

[0136] A dispersion of NaH (60% in mineral oil, 390.0 mg, 9.75 mmol) and 2,3-dihydrothieno[3,4-b]-1,4-dioxin-2-methanol (960.9 mg, 5.58 mmol) in anhydrous DMF (20 mL) under argon was heated at 60 C. for 30 minutes, and 1-bromomethylpyrene (2021 mg, 6.85 mmol) was added, the mixture was stirred for 2 hours at 60 C. Afterwards, the solvent was evaporated in vacuo and the crude was purified by silica gel column chromatography (eluent: n-hexane/AcOEt 8:1), affording an yellow powder. Finally, the powder was solubilized in CH.sub.2CL.sub.2 and precipitated using MeOH affording 3 as yellow-greenish powder (80% yield, 1.73 g).

[0137] M. f.: C.sub.24H.sub.18SO.sub.3. m. p.: 120.4-122.2 C. IR (powder): v (cm.sup.1)=2913, 2200, 2152, 2031, 1470, 1186, 1029, 908, 842, 776, 709. .sup.1H-NMR (400 MHz, CDCl.sub.3) (ppm): 3.73-3.85 (m, 2H), 4.03-4.08 (m, 1H), 4.19 (dd, 1H, J.sub.1=12 Hz, J.sub.2=8 Hz), 4.32-4.38 (m, 1H), 5.30 (d, 2H, J=4 Hz), 6.33 (dd, 2H, J.sub.1=12 Hz, J.sub.2=4 Hz), 8.02 (dd, 2H, J.sub.1=16 Hz, J.sub.2=8 Hz), 8.07 (d, 2H, J=4), 8.14 (d, 1H, J=4 Hz), 8.16 (d, 1H, J=4 Hz), 8.21 (dd, 2H, J.sub.1=12 Hz, J.sub.2=8 Hz), 8.37 (d, 1H, J=8 Hz). .sup.13C NMR (100 MHz, CDCl.sub.3): (ppm) 66.3, 68.3, 72.5, 72.8, 99.8, 99.9, 123.4, 124.6, 124.8, 125.1, 125.5, 125.5, 126.2, 127.3, 127.5, 127.8, 128.1, 129.6, 130.6, 130.9, 131.4, 131.7, 141.6, 141.7. HRMS (EI+): 386.0977 ([M].sup.+ 386.4640 calculated for [C.sub.24H.sub.18SO.sub.3]+).

Synthesis of Copolymer EDOT-Pyrene/DMT (1:10), 1

[0138] A solution of FeCl.sub.3 (1217 mg, 7.50 mmol) in AcOEt (10 mL) was slowly added into a solution of ()-62 (50.2 mg, 0.13 mmol) and 64 (388.2 mg, 1.14 mmol) in AcOEt (10 mL). The mixture was stirred at room temperature overnight, then MeOH (50 mL) was added to quench the reaction. The mixture was filtered and washed with MeOH till the waters were clear. The resultant dark powder was dissolved in 10.0 mL of CHCl.sub.3 and hydrazine (2.0 mL) was added dropwise into the solution. The mixture was concentrated in vacuo to around 10 mL and precipitated by addition of MeOH (100 mL). The solution was stirred for 10 minutes and then filtered. The precipitate was re-dissolved in 20 mL of CHCl.sub.3, re-precipitate using MeOH (150 mL) and re-filtered affording 59 as dark orange powder (42% yield)..sup.[281]m. p.: degradation before melting around 275 C. IR (powder): v (cm.sup.1)=2957, 2925, 2860, 2149, 1745, 1456, 1363, 1221, 1015, 853, 781, 721. .sup.1H NMR (400 MHz, CDCl.sub.3) (ppm) (ppm) 2.4 (m, 2H), 5.4 (s, 2H).

Wettability of the PET Surfaces.

[0139] Table 1 reports the WCA values of the PET surfaces after a treatment with organic solvents. The mixture with Toluene/CHCl.sub.3 1:5 v/v provides the lowest values of WCA that guarantee a good deposition of the blend on the plastic surface.

TABLE-US-00001 TABLE 1 Values of the contact angles of different solvents measured on PET. Solvent Contact angle () Toluene 14 DMF 16 Acetonitrile 30 THF 12 Ethyl Acetate 8.5 Toluene/CHCl.sub.3 1:1 11 Toluene/CHCl.sub.3 1:5 8

Conductivity of the Drop-Coated Solutions on PET

[0140] The values of the resistivity (measured in MO) of the drop-coated solutions on PET after the preparation of the blends are reported in Table 2 and can be used as indicator of the conductivity of the films.

TABLE-US-00002 TABLE 2 Resistivity of the drop-coated on PET of solutions for different percentages of CNT. Amount of MWCNTs in solution (%) Resistivity (M) 0.0 Not conductive 2.5 50-130 5.0 10-50 7.5 8-20 10.0 1.4-1.5 12.5 0.11-1.10 15.0 0.07-0.12

WCA Measurements for the Homogeneity of the Films

[0141] The analysis of the films by WCA is used to determine their homogeneity depending on the number of the layers and on the percentage of the MWCNTs used for the blends. FIG. 13(a) shows the trend of the WCA analysis of the films without MWCNTs, while FIG. 13(b) illustrates the results obtained for the measurement with 7.5% w of MWCNTs. The plotted values are respectively reported in Table 3 and Table 4.

TABLE-US-00003 TABLE 3 WCA measurements of the films of the copolymer 1 coated on PET, values plotted in FIG. 13(a) WCA of films of copolymer 1 Number of layers average Deviation standard 0 layers (PET surface) 73.35 1.78 1 layer 97.03 2.73 3 layers 88.60 3.50 5 layers 92.23 3.68 7 layers 86.53 2.21 9 layers 79.73 2.25

TABLE-US-00004 TABLE 4 WCA values of the films of the blend containing the 7.5% of MWCNTs coated on PET, which are plotted in FIG. 13(b). WCA of films of copolymer 1 + 0.75 mg MWCNTs Number of layers average deviationstandard 0 layers (PET surface) 73.35 1.78 1 layer 86.07 4.01 3 layers 79.27 2.54 5 layers 84.23 0.32 7 layers 81.75 0.92 9 layers 81.83 1.00

Roughness of the Films

[0142] The average roughness (Ra) and root mean square roughness (Rq) of the films without and with the 7.5% of MWCNTs have been measured by using a profilometer as measurement of their roughness. FIG. 14 illustrates a randomly distribution of the values in the case of the films without MWCNTs. When 7.5% w of MWCNTs are added, the Ra and Rq seem to reach a plateau depending on the number of layers coated on the surface.

Thickness Measured by AFM

[0143] FIG. 15 shows the Gaussian plot of the number of events depending on the height of the films, in the case where only one layer of blend is coated on the PET surface. The surface for the measurements has been prepared following the procedure described in the manuscript.

Cyclic Voltammetry at Different Percentages of MWCNTs

[0144] is coated on the PET surfaces.

[0145] FIG. 16 illustrates the cyclic voltammograms obtained for the films containing different percentages of MWCNTs. The peak at 1.5 V, registered in FIG. 8 of the manuscript, shifts at higher values of Potential (V) and Current (A) depending on the percentage of MWCNTs.

Synthesis of the Copolymer 4 and its Cyclic Voltammetry

[0146] The procedure related to the synthesis of the copolymer 4 is sketched in FIG. 17.

[0147] The resulting new copolymer has been dissolved in a mixture of chloroform-toluene in a ratio 5:1 and has been then spray-coated on PET-ITO to form a uniform orange-pink film. The plot sketched in FIG. 18 shows as expected only one cathodic peak from the thiophene unit. This confirms that the second cathodic peak observed in the pyrene-appended voltammogram comes from the pyrene moiety. This also proves that the shift observed for the second cathodic peak in the voltammogram illustrated in FIG. 8 is due to the blend of the copolymer and the MWCNTs, and especially to the - interaction between the MWCNTs and the pyrene moiety.

EXAMPLES

Example 1

[0148] The synthesis of the copolymer 1 has been designed a priori taking in consideration the three peculiarities that the material has to possess i.e. be soluble in presence of MWCNT in organic solvents, be easy to deposit on the surface and the resulting films on PET-ITO have to be as colorless as possible. To achieve the first requirement, the main monomer contains two alkyl chains in the position three and four of the thiophene ring that is able to guarantee a good solubility in organic solvents, while the second monomer, the EDOT unit, is chemically bonded to the pyrene moiety. This latter is known to make a strong - interaction with MWCNTs with the assumption to induce the blending of the copolymer 1 in the carbonaceous material. The synthesis of the monomer 2 has been achieved in a good yield using the commercially available 3-4 dimethoxyltiophene, which was poured in toluene at the temperature of 110 C. for 24 hours in presence of a catalytic amount of p-toluene sulfonic acid and the tertiary alcohol 2-ethylhexanol..sup.1 The other monomer has been successfully obtained by performing a Williamson's etherification; NaH in mineral oil has been used for the deprotonation of the primary alcohol and the 1-bromomethyl pyrene has been added to the DMF solution, giving after 2 hours of reaction the desired product 3. The polymerization of the two monomers 2 and 3 has been induced by FeCl.sub.3 in ethyl acetate with satisfactory yields (Dyer, A. L.; Craig, M. R.; Babiarz, J. E.; Kiyak, K.; Reynolds, J.; Macromolecules 2010, 43, 4460-4467).

Example 2

[0149] While the resulting copolymer 1 is soluble in most of the common organic solvents, a challenge remains for obtaining a good blend with the MWCNTs (required for future applications), owing to the bad dispersability of the carbon nanostructure (Liu C. X., Choi J. W.; Nanomaterials, 2012, 2, 329-347) and the formation of smooth and homogeneous films. We have measured the solvent contact angle of the PET surface after a treatment in organic solvents to allow the smoothest spreading of the ink on the surface (see Table 1). The optimal solvent mixture has been achieved using toluene/CHCl.sub.3 (1:5, v/v), in which the measured contact angle is just 8. Based on this value we have optimized the blends as follows: in a flat bottom vial of dimension 2*6.5 cm were added 10 mg of copolymer 1, 10 mL of CHCl.sub.3 were added in two portions of 5 mL with sonication after each addition (10 minutes at 45 C.); almost all the copolymer is dispersed in the CHCl.sub.3. The pristine MWCNTs were added in portion of 0.25 mg to check the limit of dispersability in the dark red solution with 2 mL of toluene. The solution is again sonicated during 5 minutes at 45 C. for each addition, producing a black-reddish solution in which the two components are well dispersed. Due to the darkness of the solution and the difficulties to define the presence of the sedimentation in the vial, the value of 1.50 mg of MWCNT has been considered as upper limit for the dispersability of the MWCNT in the chloroform solution of copolymer 1. In the other cases, between 0.25 and 1.25 mg of MWCNTs (corresponding to =2.5-12.5% w) no precipitates were observed over a week. FIG. 3(a) illustrates the blending procedure while FIG. 3(b) shows the picture of the solution after a week. As observed in the case of the mixture Toluene/CHCl.sub.3 (1:5, v/v), we have been able to get stable solutions using other solvents, i.e. in CHCl.sub.3 and THF. The drop casting test on PET of those solutions gave the possibility to observe the most homogenous film and also to perform a qualitative measurement of the resistivity by using a multimeter. The drop-casted samples of the solutions of blends containing 1 and p-MWCNTs gave the possibility to observe the most homogenous film and also to perform a qualitative measurement of the resistivity by using a multimeter. The best homogeneity is observed in the case of the mixture Toluene/CHCl.sub.3 (1:5, v/v) and these latter were the only conductive films on PET-ITO (between 8 and 20 nS/m).

Example 3

[0150] Due to both the versatility of the solutions containing the blend and the dimensions of the MWCNTs, the spray-coating has been chosen as technique for the coating of the solutions with and without MWCNTs on PET-ITO and/or PET. In order to accelerate the evaporation of the solvents, the surfaces have been placed on a hot plate at 40 C., allowing us to perform a systematical study of the optimal conditions to get the best device. FIG. 4 illustrates a schematic representation of the coating on PET surfaces. The amount of MWCNTs used for the blend and the number of the layers coated in the surface are the main variables considered during the systematical study, while the current applied in the device is the third variable taken under exam that is analyzed after the assembly of the device.

Example 4

[0151] The solutions coated on PET-ITO have been characterized by several techniques to confirm the first considerations concerning the homogeneity of the films. From the first analysis with the SEM microscope, the MWCNTs seem to increase the dispersability of the copolymer 1 in the organic mixture. This synergic effect is observed in the pictures illustrated in FIG. 5(a-b), on which the number of layers are kept constant, and we have observed that the films coated on PET without MWCNTs present much more rocks on the surface. The number of layers also contributes to the homogeneity of the films. We have noted that the ones composed by only one layer of blend present holes and defects that can compromise the performances of the device (FIG. 5(c)), while by coating 7 layers of the blend (FIG. 5(b)), the surfaces are more homogenous.

Example 5

[0152] The qualitative analysis made from the observations obtained with the microscope have been confirmed by the analysis of the WCA. Three tests on the same surface have been performed to get an average to be reported in a plot containing the values of the angles versus the number of layers. The standard deviation in our measurements is notably dramatically reduced after the coating of more than 3 layers of the blend copolymer 1-MWCNTs, indicating an increase in the homogeneity of the sample. In the cases of 5, 7 and 9 layers of the copolymer 1 coated on PET-ITO, the films have a standard deviation comprised between 2.21 and 3.68, while the addition of the carbonaceous material reduces it to 0.38 and 1.00. The decrease of the standard deviation is even more pronounced in comparison of the number of layers. Indeed, concerning the cases of 1 and 3 layers of the blend the values are respectively equal to 4.01 and 2.54, while as mentioned above, in the case of 5, 7 and 9 layers, the values are not higher than 1.00. FIG. 13 shows the plot of the WCA trends for the copolymer 1 and the blend with MWCNTs, while

[0153] Table and Table report the associated values. Moreover, the homogeneity of the films with 5, 7 and 9 layers of a mixture of copolymer 1+0.75 mg of MWCNTs is proven by using a profilometer. The trends of the Ra (average roughness) and Rq (root mean square roughness) seem to reach a plateau when 7 or 9 layers of the blend are coated on PET, while for the solution of copolymer 1, the two trends present a random disposition on the plot which is highlighted in FIG. 14 (see SI).

Example 6

[0154] The presence of MWCNTs in the blend coated on the surfaces has been proven by performing Transmittance Electron Microscopy (TEM) and XPS analysis. a) FIG. 6 reports the result of the TEM analysis of the blends on the metallic grid, in which the presence of the carbonaceous material as one of the components of the films is unequivocal. Moreover, the analysis of the films constituted by 9 layers of the copolymer 1 and the blend on PET put clearly in evidence, the increase of the atom percentage of C and the decrease of O and S in the film with the addition of MWCNTs. The results are presented in Table 5.

TABLE-US-00005 TABLE 5 XPS analysis of the elements C, O, S of 9 layers of the copolymer 1 and blends coated by spray on PET. % atom Copolymer 1 Copolymer 1 + 0.75 mg MWCT C 66.75 14.70 86.15 1.50 O 30.42 13.76 12.51 1.32 S 2.83 0.96 1.33 0.23

Example 7

[0155] The thickness of the different number of layers has been defined by using Atomic Force Microscopy (AFM). A metallic plate spatula covered by a cotton wool, slightly wet with Acetone, has been used to clean a part of the surface containing the films with a sharp and firm pass, making a definite rut in the surface. The surfaces have been analyzed by using the TM-AFM technique in the border of the rut and it has been possible to determine a gaussian trend of the number of the events versus the height in the scale of nm. For each film, the average on three measurements of the height at the maximum value of the gaussian trend (corresponding to the thickness of the films) is plotted versus the number of layers coated, giving a line trend, as reported in FIG. 7.

Example 8

[0156] The spray-coated thin-films over PET-ITO substrates have been characterized electrochemically. Cyclic Voltammograms showed several redox peaks with and without CNTs, and were dependent of the number of voltammogram cycles. In the first cycle (see FIG. 8), we observe 3 reduction and two oxidation peaks at 1.5 V and 1.0 V, this latter is the only peak that do not depend of the presence of CNTs (see also supplementary information). Due to the changes of coloration, the higher intensity of the peaks and the unexpected second oxidation peaks at 1.5 V, we were more interested in the study of the oxidation process. As already mentioned, the peak at 1.0 V does not depend on the percentage of MWCNTs, while is clear the trend that takes the peak at 1.5 V, this latter value increases in intensity and shifts at higher voltage values by the addition of MWCNTs. This peak has been assigned to the pyrene oxidation, after the cyclic voltammograms of the similar copolymer 4 devoid of the pyrene unit, which show the total absence of the peak at 1.5 V. The copolymer 4 is synthesized following the polymerization reaction induced by FeCl.sub.3 in AcOEt, from the monomer 2 and the commercially available EDOT, synthetic scheme and cyclic voltammogram in the SI.

Example 9

[0157] The architecture of the devices is similar to the one described for tungsten oxide electrochromic devices, where both electrodes and counterelectrodes are copolymer or copolymer+MWCNTs at different percentages, coated on PET by spray-casting, in FIG. 9(a) the schematic representation. This architecture allows the measurement of light absorption between oxidized and reduced states, since the patterns of the electrode and counter electrode are different, the monitored area is selected at one electrode, and it is not overlapped with the image printed at the other electrode. In FIG. 9(b) the picture of our ECD at the neutral state, while in the FIG. 9(c) is showed the ECD in the three different states: reduced, neutral and oxidized state respectively at 1.5 V, 0 V, and 1.5 V. A lithium-based UV curable electrolyte denominated YnvEI described on the patent no US20140361211A1 separates the two electrodes and the device is closed and sealed.

Example 10

[0158] The optical properties of the copolymer/CNT thin-films in the electrochromic devices have been characterized by spectroelectrochemistry in the wavelength range of 300-800 nm and voltage range of 1.5 to 1.5 V. The measurements were made on a solid-state electrochromic cell, which contained all the components of the device, including the TCO and electrolyte layers. FIG. 10 shows the change in absorbance (AA) when a voltage is applied on the device, between the blue (i.e., positive voltage, oxidized copolymer) and the orange (i.e., negative voltage, reduced copolymer) states, the addition of the MWCNTs at the value of 7.5% w has a positive effect in the device, increasing the AA of the neutral and oxidized state.

Example 11

[0159] Thanks to the spectroelectrochemistry analysis we have been able to determine the general features of an electrochromic device. By increasing the percentage of MWCNTs in the blend preparation, the most noticeable effect is the increase of A, probably due to a more efficient electron-injection into the thin-layer but it may also be caused by the increased thickness of the thin-films when MWCNTs are present. The most dramatic effect is shown on Table 6 and FIG. 11 where the reduction switching times, .sub.red, decrease by one order of magnitude (from 4 s to about 300 ms) by addition of 7.5% w of MWCNTs, while oxidation switching time, .sub.0x, remains fairly constant. In the same case another remarkable features are observed, namely equal values of total charge in oxidation and reduction cycles (Q.sub.ox and Q.sub.red), which are important for the electrochemical stability of the devices. Also the Coloration efficiency (CE) increases although the effect is not very pronounced. The remarkable effect on .sub.red indicates a very fast electron-injection in the thin-film, promoted by the presence of MWCNTs. The value is indeed one of the fastest when compared with previous literature. In the supplementary material a real-time video shows the difference of performance between electrochromic devices without and with MWCNTs.

[0160] The applied voltage has also an important role. As expected, for values below 1 V the optical activity is negligible. The optimal effect is reached with 1.5 V, since above some degradations start to occur due to secondary electrochemical reactions. The number of layers mainly influences the oxidation switching time, which decreases to about 1 s when only 1 layer is deposited in the presence of 7.5% MWCNTs.

TABLE-US-00006 TABLE 6 Electric current, transition time between redox states, coloration efficiency, change in absorbance and in transmittance of assembled electrochromic devices. Influence of CNT (E = 1.5 V, 9 layers) Q.sub.red Q.sub.ox CE .sub.ox .sub.red % CNT (mC .Math. cm.sup.2) (mC .Math. cm.sup.2) % T Abs (cm.sup.2 C.sup.1) (s) (s) 0 0.89 1.13 12.9% 0.097 71.5 4.6 3.8 2.5 1.09 1.08 14.5% 0.107 90.8 4.9 0.5 5.0 1.22 1.16 13.8% 0.103 80.0 4.6 0.3 7.5 1.33 1.36 17.8% 0.148 99.2 3.6 0.3 10.0 1.82 1.62 18.9% 0.190 98.9 6.6 0.3 Influence of E (7.5% CNT, 9 layers) Q.sub.red Q.sub.ox CE .sub.ox .sub.red E/V (mC .Math. cm.sup.2) (mC .Math. cm.sup.2) % T Abs (cm.sup.2 C.sup.1) (s) (s) 0.5 0.05 0.05 0.6% 0.008 84.8 16.0 14.0 1.0 0.24 0.25 6.4% 0.060 220.5 11.0 0.9 1.25 0.65 0.71 16.6% 0.142 189.5 3.1 0.4 1.5 1.33 1.36 17.8% 0.148 96.6 3.6 0.3 1.8 2.26 2.64 18.8% 0.166 58.0 2.5 0.3 Influence of number of layers (7.5% CNT, E = 1.5 V) Q.sub.red Q.sub.ox CE .sub.ox .sub.red layers (mC .Math. cm.sup.2) (mC .Math. cm.sup.2) % T Abs (cm.sup.2 C.sup.1) (s) (s) 3 0.47 0.58 9.3% 0.061 106.8 1.1 0.2 6 0.91 0.93 10.5% 0.078 77.4 2.3 0.2 9 1.33 1.36 17.8% 0.148 99.2 3.6 0.3 12 1.99 1.93 18.1% 0.172 81.8 7.1 0.4 15 2.10 2.10 18.6% 0.177 79.4 7.3 0.5

[0161] A special room has been used to calculate the color coordinates during the electrochromic transition of the solid-state cell, equipped with a digital camera under diffuse light inside.

[0162] Afterwards the pictures were analyzed by calibration with a ColorChecker, in order to calculate L*, a* and b*. These results were then converted to color contrast values E* using the oxidized state as reference (1.5 V) at the first cycle, after calculating L*, a* and b*:.sup.i

L*=|L*.sub.oxL*(t)|(1a)

a*=|a*.sub.oxa*(t)|(1b)

b*=|b*.sub.oxb*(t)|(1c)

E*={square root over ((L*).sup.2+(a*).sup.2+(b*).sup.2)}(d)

[0163] The FIG. 12(a-b) shows the E depending on the number of cycles applied to the device. The resulting film coated on the surface without MWCNTs shows a significant degradation after 2000 cycles (see FIG. 12(a)), while the film containing the 7.5% of MWCNTs after 10000 cycles the device degradation is still rather small (see FIG. 12(b)). In the plots shown in FIG. 12(c), the zigzag trend represents the transmittance values of the device without (red trend) and with the addition of 7.5% of MWCNTs (dark trend). Moreover, to have a direct comparison of the endurance of the two different devices, in the same plot are compared the transmittance values at the first cycles and after 16000 cycles. After this treatment, the device without MWCNTs does not present anymore changes in term of transmittance, that is a direct proof of the total decay of the device, while in the case of the device with MWCNTs the grey part shows a transmittance that is rather the same with respect to the transmittance after the first cycles (black trend). With the same technique, we were able to run four different devices having different amounts of MWCNT in the blend, checking the E depending on the number of cycles. The plot illustrated in Figure (d) clearly shows how the addition of the carbonaceous material increases the life of the device. After 40.000 cycles, the device containing 7.5% of MWCNTs loses just the half of the E.sub.0, while in the case of 0% of MWCNTs the device loses any electrochromic activities after 10.000 cycles. By increasing the percentage of MWCNTs (10%) we observe that there is no substantial improvement of the device.

Example 12

[0164] The synthesis of the new copolymer 1 and its mixture of MWCNTs allows to obtain stable solutions in organic solvents of the two components, thanks to the solubilizing properties of the alkyl chains and pyrene unit present in the two different monomers, that with a strong - interaction interacts with the MWCNTs. The formulation of a stable solution and the choose of the spray coating give the chance to prepare homogenous films that are characterized by several techniques. The morphological and electrochemical characterizations of the films prove the direct correlation between the homogeneity of the films and the performances of the devices, that in our case are associated to the switching times (.sub.red) and the endurance (number of cycles). Moreover the performances of the device are improved by adding a certain percentage of MWCNTs, corresponding to the 7.5% w with respect to copolymer 1. The reason for the outstanding stability of the devices with MWCNTs may be connected with secondary electrochemical processes (e.g., degradation of electrolyte layer) which are prevented by MWCNTs. For the electrochemical stability of the devices, the difference in the total charge in the oxidation and reduction cycles (Q.sub.ox and Q.sub.red) is also important. By adding 7.5% MWCNTs, the difference in terms of the total charge values during the redox process is very small. The most plausible explanation is that MWCNTs will scavenge the excess electric charges injecting them back to the ITO layer. Through the systematical studies, which has been made possible only by the formulation of a stable blend of copolymer 1 and MWCNTs, we have found that the characteristics to obtain the best ECD are the following: 9 layers of the blend on PET-ITO containing the 7.5% w of MWCNTs with respect to copolymer 1 with an applied voltage of 1.5 V.