MONO-AZIDE COMPOUND FOR PHOTO-INDUCED CROSS-LINKING POLYMER STRANDS

Abstract

The present invention relates to the use of a mono-azide compound for cross-linking polymer strands, wherein said mono-azide compound has a structure of the formula (I): (I), wherein Q.sup.1 and Q.sup.2 are each independently from another a halogen and wherein R.sup.1, R.sup.2 and R.sup.3 are each independently from another any not comprising an azido moiety. Further, the present invention relates to a method for cross-linking polymer stands and to a cross-linked polymer composition obtainable from said method and an electronic device comprising such composition.

##STR00001##

Claims

1-15. (canceled)

16. A method for cross-linking polymer strands, the method comprising: providing a composition comprising (A) the polymer strands, (B) a mono-azide compound of the formula (I): ##STR00006## wherein: Q.sup.1 and Q.sup.2 are each independently from another each a halogen, and R.sup.1, R.sup.2 and R.sup.3 are each independently from another any residue not comprising an azido moiety, and (C) optionally one or more solvent(s); (ii) irradiating said composition of step (i) with light of a wavelength in the range of from 200 nm to 450 nm; (iii) optionally removing one or more solvents from the sample; and (iv) obtaining a cross-linked polymer composition.

17. The method according to claim 16, wherein Q.sup.1 and Q.sup.2 are both F.

18. The method according to claim 16, wherein: R.sup.1, R.sup.2 and R.sup.3 are each an electron withdrawing and/or water-soluble group; R.sup.a, R.sup.b and R.sup.e are each independently from another selected from hydrogen, halogen, or an unsubstituted or substituted residue of not more than 20 carbon atoms selected from the group consisting of alkyl, alkenyl, alkinyl, heteroalkyl, heteroalkenyl, heteroalkinyl, aryl, alkaryl, arylalkyl, heteroaryl, heteroarylalkyl, and heteroalkaryl; R.sup.d is a bivalent residue of not more than 20 carbon atoms; and X.sup.− is a counter ion.

19. The method according to claim 16, wherein at least one of R.sup.1, R.sup.2 and R.sup.3 is an electron withdrawing residue.

20. The method according to claim 16, wherein at least two of R.sup.1, R.sup.2 and R.sup.3 are each independently from another a halogen.

21. The method according to claim 16, wherein the polymer strands are selected from the group consisting of poly(vinylpyridine), poly(vinylbenzyl chloride), polyvinyltoluene, poly(2-vinylnaphtalene), polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polyacrylonitrile, poly(vinylphenol), polyethylene, polypropylene, polymethylpentene, polybutadiene, polybutene-1, polyisobutylene, ethylene propylene rubber, and ethylene propylene diene monomer rubber, polyethalene oxide, polyethylene glycol methyl ester, poly(methacrylate), poly(methyl methacrylate) polycaprolactone, polylactic acid, polymalic acid, polystyrene, poly(alpha-methyl styrene), polystyrene-co-maleic anhydrate, poly(ethylene oxide), and copolymers of two or more thereof.

22. The method according to claim 16, wherein the step (ii) of irradiating is excitation with light of a wavelength in the range of from 200 nm to 400 nm.

23. The method according to claim 16, wherein prior to step (ii) of irradiating, the composition of step (i) is brought into a laminar extension of a thickness of less than 1 mm.

24. The method according to claim 23, wherein the composition of step (i) is brought into a laminar extension by means of spin coating, solution casting, spraying, slot die coating and/or printing.

25. The method according to claim 16, wherein the step (ii) of irradiating is excitation an amount of irradiation energy in the range of from 100 mJ/cm.sup.2 to 100 J/cm.sup.2.

26. The method according to claim 16, wherein said method further comprises: (v) removing: residual mono-azide compound of the formula (I); reaction products of the mono-azide compound of the formula (I); and/or polymer strands cross-linked to a low degree or non-cross-linked.

27. A cross-linked polymer composition obtainable from the method according to claim 16.

28. An electronic device, comprising the cross-linked polymer composition according to claim 27.

Description

FIGURES

[0097] FIG. 1 shows an .sup.19F-NMR of the azido pentafluorobenzene (PFPA): main peaks are located at −151.6 ppm, −159.8 ppm, and −161.6 ppm at signal intensities 2:1:2. Herein, the following parameters were set: frequency (MHz): (f1) 375.638, original points count: (f1) 131072, acquisition time (sec): (f1) 1.0000, spectral width (ppm): (f1) 207.980, temperature: 25°, number of scans: 16.

[0098] FIG. 2 shows a representative example of the cured PVPyr/PFPA film on Si/SiO.sub.2 prior to rinsing.

[0099] FIG. 3 shows a representative example of the cured PVPyr/PFPA film on Si/SiO.sub.2 after the rinsing test.

[0100] FIG. 4 shows a diagram of k over frequency for cured PVPyr/PFPA films on ITO. The indexes give the content of PFPA (wt-%).

[0101] FIG. 5 shows a representative example of output (FIG. 5B) and transfer curves (FIG. 5A) for a BGTC device using a cured PVPyr/PFPA dielectric at V.sub.d=−30 V (W/L=50).

EXAMPLES

Example 1

[0102] Synthesis of Azido pentafluorobenzene (PFPA):

##STR00005##

[0103] In a 250 mL three-neck round bottom flask equipped with thermometer, magnetic stirrer bar and cooling bath, 2,3,4,5,6-pentafluoroaniline (4.2 g, 23.1 mmol) was dissolved in trifluoroacetic acid (50 mL) at −10° C. Sodium nitrite (3.15 g, 45 mmol) was added slowly in small portions and the mixture was stirred for 2 h, while keeping the temperature constant. Then sodium azide (3.15 g, 48 mmol) was added to the solution within 10 min and the solution was stirred for 1 h. Subsequently, water (100 mL) was poured into the reaction mixture, which was allowed to warm to room temperature. The product was obtained by extraction with n-hexane (3×50 mL). The combined organic phases were washed with sodium bicarbonate (saturated solution) in order to neutralize the remaining trifluoroacetic acid. Subsequently, the solution was washed with water (50 mL) and dried over sodium sulfate. After evaporation of the solvent (rotary evaporator), 1-azido-2,3,4,5,6-pentafluorobenzene was obtained as a dark red to brown oil, pure by .sup.19F-NMR (3.54 g, 16.9 mmol, 73%). (TLC in DCM/hexanes 1:1 shows R.sub.f of product: 0.75, R.sub.f of starting material: 0.55). A respective .sup.19F-NMR spectrum is depicted in FIG. 1 herein. A suitable synthesis for obtaining PFPA is also depicted in U.S. Pat. No. 3,238,230.

Example 2

Formulation of PFPA and Poly(vinylpyridine) (PVPyr)

[0104] Poly-4-vinylpyridine (Mn=60,000, 2.60 g) was dissolved in c-pentanone (36.0 mL) to give a slightly yellow solution with a concentration of c=72.2 mg/mL=1.20.Math.10.sup.−6 mol/mL=1.2 mM. The polymer solution was split into samples of 4 mL each and treated with neat PFPA as follows. After stirring for 60 sec, homogenous solutions of the PVPyr/PFPA were obtained:

TABLE-US-00001 TABLE 1 Representative example for the preparation of PVPyr/PFPA solutions (I). amount of mono-azide (PFPA) sample type V.sub.sol. [μL] C.sub.PVPyr. final [mg/mL] neat PVPyr 0 72.2  10 mol-% PFPA (0.04 wt-%) 20 71.8  30 mol-% PFPA (0.12 wt-%) 60 71.1  50 mol-% PFPA (0.18 wt-%) 100 70.4 100 mol-% PFPA (0.36 wt-%) 200 68.8

[0105] To further improve film thicknesses (c. p. below) and reproducibility, PVPyr/PFPA solutions with a constant polymer concentration were prepared by mixing varying amounts of PFPA with a polymer stock solution of c C.sub.PVPyr=90.0 mg/mL=1.50.Math.10.sup.−6 mol/mL=1.5 mM as follows:

TABLE-US-00002 TABLE 2 Representative example for the preparation of PVPyr/PFPA solutions (II). amount of mono-azide amount of (PFPA) PVPyr solution Sample type m.sub.PFPA [mg] C.sub.PVPyr = 90 mg/mL  100 mol-% PFPA (0.36 wt-%) 5 15.4 1000 mol-% PFPA (3.60 wt-%) 20 6.2 3000 mol-% PFPA (11.3 wt-%) 60 6.2 6000 mol-% PFPA (21.6 wt-%) 120 6.2

Example 3

Preparation and Characterization of the Thin Film Samples

[0106] All preparation steps were conducted under ambient air. Si/SiO.sub.2 wafer samples (2×2 cm) and ITO samples (2×2 in) were cleaned by immersing them in isopropanol and acetone and subsequent blow-drying in a N.sub.2 stream (55 psi). The procedure was repeated three times before drying the substrates at 90° C. for 5 min. The obtained solutions were spin coated at 1500 rpm, (255 asc, 22° C.) for 30 sec onto the cleaned Si/SiO.sub.2 wafer and ITO samples, respectively. 150 μL of polymer solution was used for the Si/SiO.sub.2 wafer sample, 200 μL for the ITO samples. After drying at 90° C. for 30 sec, smooth, transparent and hard films were obtained.

[0107] Photocuring was done using a 254 nm monochromatic UV lamp at a constant output of 2.97 mW/cm.sup.2 for 10 min, equaling an energy input of 1,785 mJ/cm.sup.2. Film thicknesses were obtained using a profile meter device. The rinsing tests were performed by immersing the samples in c-pentanone for 60 sec, followed by blow-drying in a N.sub.2 stream (55 psi) and further drying the substrates at 90° C. for 5 min. The retention factor was determined by comparison of the measured film thicknesses prior to and after the rinsing step. For each PFPA loading, at least two identical samples were prepared and characterized. A representative example is given as follows:

TABLE-US-00003 TABLE 3 Comparison of films before and after rinsing sample: 100 mol-% PFPA film thicknesses [nm] (0.36 wt-%) measurement no. C.sub.PVPyr = 68.8 mg/mL 1 2 3 avg. retention factor before rinsing A 313 317 310 313 B 303 306 314 308 after rinsing A 292 295 299 295 94% B 292 286 294 291 94%

[0108] An exemplary microscopic image of the PVPyr/PFPA film on the Si/SiO.sub.2 wafer before rinsing is depicted in FIG. 2 herein. An exemplary microscopic image of the PVPyr/PFPA film on the Si/SiO.sub.2 wafer after rinsing is depicted in FIG. 3 herein.

Example 4

[0109] Determination of k-Values and Device Characteristics

[0110] Dielectric constants were obtained by capacitance measurements on the spin-coated ITO substrates. Evaporated Au (d≈70 nm) dots with an area of 7.85×10.sup.−7 m.sup.2 were used as counter electrodes. Five datapoints were recorded for every substrate, and two substrates were characterized for every of the abovementioned PFPA concentrations. Film thicknesses were optimized to be at least 500 nm by using a polymer concentration of 90.0 mg/mL (cp. above). FIG. 4 and Table 4 show the representative k-values for PVPyr/PFPA films in a frequency range from 1 kHz to 1 MHz.

TABLE-US-00004 TABLE 4 k over frequency for cured PVPyr/PFPA films on ITO. k over frequency sample 1 kHz 10 kHz 100 kHz 1 MHz avg. PFPA-0.4 4.68 4.54 4.45 4.24 4.48 PFPA-4.0 4.42 4.32 4.24 4.16 4.29 PFPA-11 4.58 4.48 4.39 4.32 4.44 PFPA-22 4.45 4.33 4.23 4.09 4.28

[0111] Representative data for the determination of k-values for a sample containing 100 mol-% PFPA (0.36 wt-%) is given herein.

TABLE-US-00005 TABLE 5 Data for the determination of k-values for two samples each containing 100 mol-% PFPA. SAMPLE 1 Dielectric: PVPyr-PFPA Area (m.sup.2) 7.85E−07 Thickness (nm) 572 ε0 8.85E−12 C.sub.Point 1 C.sub.Point 3 C.sub.Point 4 C.sub.Point 5 Average f (Hz) (pF) C.sub.Point 2 (pF) (pF) (pF) (pF) (pF) ε 20 39.5 19.1 39.7 38.9 39.0 35.2 2.90 40 57.4 58.3 57.6 56.7 58.3 57.7 4.75 120 64.4 65.4 64.9 63.7 64.8 64.6 5.32 350 57.6 57.2 57.8 56.7 57.9 57.4 4.73 1000 59.9 56.9 57.2 56.2 57.2 57.5 4.73 4000 56.2 56.3 56.4 55.4 56.4 56.1 4.62 10000 55.7 55.7 55.9 54.9 55.9 55.6 4.58 100000 54.7 54.6 54.7 53.9 54.8 54.5 4.49 1000000 53.9 52.0 52.4 51.2 52.7 52.4 4.32 Mean Dissipation f (Hz) D1 D2 D3 D4 D5 factor 20 4.73E−01 1.02E+02 4.46E−01 4.87E−01 4.68E−01 2.08E+01 40 4.60E−02 1.63E+01 5.11E−02 4.80E−02 4.70E−02 3.30E+00 120 4.40E−02 5.17E+00 4.70E−02 4.30E−02 4.70E−02 1.07E+00 350 1.20E−02 2.06E+00 1.60E−02 1.50E−02 1.30E−02 4.23E−01 1000 1.50E−02 7.39E−01 1.70E−02 1.70E−02 1.70E−02 1.61E−01 4000 1.40E−02 2.12E−02 1.60E−02 1.50E−02 1.60E−02 1.64E−02 10000 1.40E−02 9.70E−02 1.70E−02 1.60E−02 1.60E−02 3.20E−02 100000 1.80E−02 4.00E−02 3.70E−02 3.10E−02 2.90E−02 3.10E−02 1000000 5.60E−02 1.95E−01 1.79E−01 1.80E−01 1.62E−01 1.54E−01 SAMPLE 2 Dielectric: PVPyr-PFPA Area (m.sup.2) 7.85E−07 Thickness (nm) 577 ε0 8.85E−12 C.sub.Point 3 C.sub.Point 4 C.sub.Point 5 Average f (Hz) C.sub.Point 1 (pF) C.sub.Point 2 (pF) (pF) (pF) (pF) (pF) ε 20 39.8 38.6 39.0 37.6 37.6 38.5 3.197635 40 57.4 56.1 56.5 56.0 55.7 56.3 4.676915 120 63.8 62.5 62.9 62.5 62.6 62.9 5.218156 350 56.8 55.6 55.7 55.4 55.6 55.8 4.633749 1000 56.2 54.9 55.1 54.7 54.9 55.2 4.578961 4000 55.4 54.0 54.3 54.0 54.1 54.4 4.512551 10000 54.9 53.6 53.8 53.5 53.6 53.9 4.472705 100000 53.8 52.5 52.8 52.4 52.3 52.8 4.379731 1000000 52.5 51.8 51.8 50.3 40.2 49.3 4.094169 Mean Dissipation f (Hz) D1 D2 D3 D4 D5 factor 20 4.73E−01 1.02E+02 4.46E−01 4.87E−01 4.68E−01 2.08E+01 40 4.60E−02 1.63E+01 5.11E−02 4.80E−02 4.70E−02 3.30E+00 120 4.40E−02 5.17E+00 4.70E−02 4.30E−02 4.70E−02 1.07E+00 350 1.20E−02 2.06E+00 1.60E−02 1.50E−02 1.30E−02 4.23E−01 1000 1.50E−02 7.39E−01 1.70E−02 1.70E−02 1.70E−02 1.61E−01 4000 1.40E−02 2.12E−02 1.60E−02 1.50E−02 1.60E−02 1.64E−02 10000 1.40E−02 9.70E−02 1.70E−02 1.60E−02 1.60E−02 3.20E−02 100000 1.80E−02 4.00E−02 3.70E−02 3.10E−02 2.90E−02 3.10E−02 1000000 5.60E−02 1.95E−01 1.79E−01 1.80E−01 1.62E−01 1.54E−01

TABLE-US-00006 TABLE 6 Summary of the results. Dielectric Constant Dissipation Factor f (Hz) S1 S2 S3 mean error S1 S2 S3 mean error 20 2.90 3.20 2.90 3.00 0.17 20.755 20.755 20.755 20.755 0.000 40 4.75 4.68 4.75 4.72 0.04 3.298 3.298 3.298 3.298 0.000 120 5.32 5.22 5.32 5.29 0.06 1.070 1.070 1.070 1.070 0.000 350 4.73 4.63 4.73 4.70 0.05 0.423 0.423 0.423 0.423 0.000 1000 4.73 4.58 4.73 4.68 0.09 0.161 0.161 0.161 0.161 0.000 4000 4.62 4.51 4.62 4.58 0.06 0.016 0.016 0.016 0.016 0.000 10000 4.58 4.47 4.58 4.54 0.06 0.032 0.032 0.032 0.032 0.000 100000 4.49 4.38 4.49 4.45 0.06 0.031 0.031 0.031 0.031 0.000 1000000 4.32 4.09 4.32 4.24 0.13 0.154 0.154 0.154 0.154 0.000

Example 5

Fabrication of the Bottom-Gate-Top-Contact OFET Devices

[0112] All preparation steps were conducted under ambient air. Si/SiO.sub.2 wafer samples (1×1 cm) were cleaned by immersing them in isopropanol and acetone and subsequent blow-drying in a N.sub.2 stream (55 psi). The procedure was repeated three times before drying the substrates at 90° C. for 5 min. The obtained solutions were spin coated at 1500 rpm, (255 asc, 22° C.) for 30 sec onto the cleaned Si/SiO.sub.2 wafer samples. After drying at 90° C. for 30 sec, smooth, transparent and hard films were obtained. Photocuring was done using a 254 nm monochromatic UV lamp at a constant output of 2.97 mW/cm.sup.2 for 10 min, equaling an energy input of 1,785 mJ/cm.sup.2. Afterwards, the samples were immersed in c-pentanone for 60 sec, followed by blow-drying in a N.sub.2 stream (55 psi) and further drying the substrates at 90° C. for 5 min. The P1100 polymeric semiconductor (0.75 wt-% in o-xylene) was spin-coated on top of the dielectric at 1000 rpm (255 asc, 22° C.) for 30 sec, followed by drying at 90° C. for 30 sec. Evaporated Au (d≈70 nm) was used as source and drain electrodes. Characterization was performed using a typical three electrode setup. Table 7 gives an overview of the obtained figures of merit for a representative BGTC device.

TABLE-US-00007 TABLE 7 Merit for a representative BGTC device (W/L = 50, Id = −30 V). μ [cm.sup.2/Vsec] 2.5 × 10.sup.−1 I.sub.ON/OFF [A] 6.6 × 10.sup.3   I.sub.leak [A] 7.2 × 10.sup.−9

[0113] These results are further depicted in FIG. 5 herein.

Example 6

Comparison of the Cross-Linking of a Varienty of Polymers

[0114] The following (co)polymers were tested for their ability to be cross-linked by PFPA:

poly(vinylpyridine) (PVPyr), M.sub.w=60 k;
poly(2-vinylnaphthalene) (PVN), M.sub.w=175 k;
poly(vinylbenzyl chloride) (PVBC), M.sub.w=40.5 k;
polyvinyltoluene (PVT), M.sub.w=72 k;
poly(alpha-methylstyrene) (PαMS), M.sub.n=1,300;
polycaprolactone (PCL), M.sub.n=45 k;
poly(vinylphenol)/poly(methyl methacrylate) copolymer (PVP/PMMA);
polystyrene-co-maleic anhydrate copolymer (PS/MA);
polybutadiene (PBD), M.sub.w=20 k;
poly(methyl methacrylate) (PMMA), M.sub.w=996 k;
polyethylene glycol methyl ether 5,000 (PEGME); and
poly(ethylene oxide) (PEO), M.sub.v=300 k.

[0115] Samples of these polymers were dissolved in a solvent. Then, 4% (w/w) PFPA were added to such solutions. The solutions were irradiated for 10 min at 254 nm by means of a monochromatic UV lamp at a constant output of 2.97 mW/cm.sup.2. Subsequently, the formed immersions were maintained in the original solvent for 1 min and the retention was determined via filtration. The results are depicted below:

TABLE-US-00008 TABLE 8 Comparative results og the cross-linking of a varienty of polymers polymer Solvent c [mg/mL] d.sub.cured [nm] d.sub.rinsed [nm] retention [%] PVPyr c-pentanone 70 303, 306, 314, 292, 286, 93-97% (±2) 294 (±2) PVPyr c-pentanone 90 736, 733, 731 733, 728,  98-100% (±1) 719 (±2) PVN c-pentanone 70 450, 426, 406 332, 266, 61-74% (±1) 246 (±2) PVBC c-pentanone 90 875, 568, 389 686, 453, 77-78% (±1) 386 (±1) PVT c-pentanone 90 1054, 1000, 866, 858, 82-87% 958 (±2) 835 (±2) PαMS c-pentanone 90 629, 574, 532 NO RETENTION (±2) PCL c-pentanone 90 940, 870, 735 NO RETENTION (±2) PVP/PMMA c-pentanone 90 658, 644, 633 NO RETENTION (±2) PS/MA c-pentanone 90 693, 688, 685 NO RETENTION (±1) PBD c-pentanone 90 N/A (no solid film formed, resinous polymer) PMMA c-pentanone 45 234, 225, 220 NO RETENTION (±2) PMMA NMP 45 535, 515, 500 477, 440, 85-89% (±2) 422 (±5) PEGME NMP 90 N/A (no film formed, low viscosity) PEO NMP <30 (sat.)** 99, 68, 57 104, 82, 54 79-82%

[0116] This experiment provides evidence that a large variety of polymers show significant retention upon cross-linking initialized by the compound of the present invention. As the reaction conditions were so far not finally optimized, also the polymers showing no significant retention herein may be cross-linked by means of a compound of the present invention to a certain degree upon modifying the reaction conditions.

REFERENCES

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