COMPOSITIONS COMPRISING FUNCTIONALIZED POLYVINYL ALCOHOL AND NANOCAPSULES CONTAINING A LIQUID-CRYSTALLINE MEDIUM

Abstract

The use of functionalized polymerizable polyvinyl alcohol as a binder or matrix for a dispersion of nanoparticles, wherein the nanoparticles respectively comprise a polymeric shell and a core containing a liquid crystalline medium. Composites comprising the functionalized polymer and the nanocapsules, methods for preparing the composites and electro-optical devices containing such composites.

Claims

1. A method for preparing a composite, wherein the method comprises (i) providing nanocapsules which respectively comprise a polymeric shell and a core containing a liquid crystalline medium, and (ii) mixing the nanocapsules with a polymer comprising one or more of the repeating units A and/or B ##STR00243## and one or more of the repeating units C and/or D ##STR00244## wherein Sp.sup.1 and Sp.sup.2 respectively represent a spacer group, X.sup.11 represents CH.sub.2, CO, SCO or NHCO, y is, independently in each occurrence, 0 or an integer from 1 to 10, X.sup.12 represents, independently in each occurrence, O, S, CO, NH or an ester group, X.sup.13 represents, independently in each occurrence, O, S, CO, NH or single bond, and R.sup.11 is a polymerizable group.

2. The method according to claim 1, wherein the polymer which is mixed with the nanocapsules in step (ii) has an average molecular weight within the range of 5,000 g/mol to 250,000 g/mol.

3. The method according to claim 1, wherein the amount of the repeating unit A in the polymer as a whole is in the range from 0 to 90 mol %, and/or the amount of the repeating unit B in the polymer as a whole is in the range from 1 mol % to 98 mol %, and/or the amount of the repeating unit C in the polymer as a whole is in the range from 0 mol % to 80 mol %, and/or the amount of the repeating unit D in the polymer as a whole is in the range from 0 mol % to 80 mol %, wherein at least one of the repeating units C and D is present, and wherein the combined amounts of the repeating units A, B, C and D, if respectively present, in the polymer as a whole are 100 mol % or less.

4. The method according to claim 1, wherein R.sup.11 is an acryloyl group or a methacryloyl group.

5. The method according to claim 1, wherein di- or multireactive monomeric or oligomeric polymerizable compounds are further comprised in the composite.

6. The method according to claim 1, wherein in step (ii) the nancapsules are dispersed in the polymer, and wherein subsequently the dispersion is arranged as a layer supported on a substrate or as a layer between two opposing substrates.

7. The method according to claim 1, wherein the method further comprises polymerization of the polymerizable groups of the prepared composite.

8. A composite obtained by carrying out the method according to claim 1.

9. A composite, comprising nanocapsules which respectively comprise a polymeric shell and a core containing a liquid crystalline medium, and a polymer containing the nanocapsule dispersed therein comprising one or more of the repeating units A and/or B and one or more of the repeating units C and/or D: ##STR00245## wherein Sp.sup.1 and Sp.sup.2 respectively represent a spacer group, X.sup.11 represents CH.sub.2, CO, SCO or NHCO, y is, independently in each occurrence, 0 or an integer from 1 to 10, X.sup.12 represents, independently in each occurrence, O, S, CO, NH or an ester group, X.sup.13 represents, independently in each occurrence, O, S, CO, NH or single bond, and R.sup.11 is a polymerizable group.

10. The composite according to claim 9, wherein the liquid crystalline medium comprises one or more compounds of formula I
R-A-Y-A-R(I) wherein R and R denote, independently of one another, a group selected from F, CF.sub.3, OCF.sub.3, CN, and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or mono- or polysubstituted by halogen and wherein one or more CH.sub.2 groups may be, in each case independently of one another, replaced by O, S, CO, COO, OCO, OCOO or CC in such a manner that oxygen atoms are not linked directly to one another, A and A denote, independently of one another, a group selected from -Cyc-, -Phe-, -Cyc-Cyc-, -Cyc-Phe-, -Phe-Phe-, -Cyc-Cyc-Cyc-, -Cyc-Cyc-Phe-, -Cyc-Phe-Cyc-, -Cyc-Phe-Phe-, -Phe-Cyc-Phe-, -Phe-Phe-Phe- and the respective mirror images thereof, wherein Cyc is trans-1,4-cyclohexylene, in which one or two non-adjacent CH.sub.2 groups may be replaced by O, and wherein Phe is 1,4-phenylene, in which one or two non-adjacent CH groups may be replaced by N and which may be substituted by one or two F, and Y denotes single bond, COO, CH.sub.2CH.sub.2, CF.sub.2CF.sub.2, CH.sub.2O, CF.sub.2O, CHCH, CFCF or CC.

11. The composite according to claim 10, wherein one or more compounds of the formula I are selected from the compounds of formulae Ia, Ib, Ic and Id ##STR00246## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 denote, independently of one another, straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or mono- or polysubstituted by halogen and wherein one or more CH.sub.2 groups may be, in each case independently of one another, replaced by O, S, CO, COO, OCO, OCOO or CC in such a manner that oxygen atoms are not linked directly to one another, X.sup.1 and X.sup.2 denote, independently of one another, F, CF.sub.3, OCF.sub.3 or CN, L.sup.1, L.sup.2, L.sup.3, L.sup.4 and L.sup.5 are, independently of one another, H or F, i is 1 or 2, and j and k are, independently of one another, 0 or 1.

12. A switching layer, comprising nanocapsules which respectively comprise a polymeric shell and a core containing a liquid crystalline medium, wherein the nanocapsules are dispersed in a polymeric binder which comprises a polymer obtained by polymerizing a polymer comprising one or more of the repeating units A and/or B and one or more of the repeating units C and/or D: ##STR00247## wherein Sp.sup.1 and Sp.sup.2 respectively represent a spacer group, X.sup.11 represents CH.sub.2, CO, SCO or NHCO, y is, independently in each occurrence, 0 or an integer from 1 to 10, X.sup.12 represents, independently in each occurrence, O, S, CO, NH or an ester group, X.sup.13 represents, independently in each occurrence, O, S, CO, NH or single bond, and R.sup.11 is a polymerizable group.

13. A light-modulation element which comprises a composite according to claim 8.

14. A light-modulation element which comprises a switching layer according to claim 12.

15. An electro-optical device, comprising a composite according to claim 8.

16. An electro-optical device, comprising ae switching layer according to claim 12.

17. A method which comprises dispersing nanoparticles which respectively comprise a polymeric shell and a core containing a liquid crystalline medium, with a polymer comprising one or more of the repeating units A and/or B ##STR00248## and one or more of the repeating units C and/or D ##STR00249## wherein Sp.sup.1 and Sp.sup.2 respectively represent a spacer group, X.sup.11 represents CH.sub.2, CO, SCO or NHCO, y is, independently in each occurrence, 0 or an integer from 1 to 10, X.sup.12 represents, independently in each occurrence, O, S, CO, NH or an ester group, X.sup.13 represents, independently in each occurrence, O, S, CO, NH or single bond, and R.sup.11 is a polymerizable group.

18. The composite of claim 9, wherein the polymer has an average molecular weight within the range of 5,000 g/mol to 250,000 g/mol.

19. The composite of claim 9, wherein the amount of the repeating unit A in the polymer as a whole is in the range from 0 to 90 mol %, and/or the amount of the repeating unit B in the polymer as a whole is in the range from 1 mol % to 98 mol %, and/or the amount of the repeating unit C in the polymer as a whole is in the range from 0 mol % to 80 mol %, and/or the amount of the repeating unit D in the polymer as a whole is in the range from 0 mol % to 80 mol %, wherein at least one of the repeating units C and D is present, and wherein the combined amounts of the repeating units A, B, C and D, if respectively present, in the polymer as a whole are 100 mol % or less.

20. The composite of claim 9, wherein R.sup.11 is an acryloyl group or a methacryloyl group.

21. The composite of claim 9, wherein R.sup.11 is one of the following groups: CH.sub.2CW.sup.1COO, ##STR00250## CH.sub.2CW.sup.2(O).sub.k1, CH.sub.3CHCHO, (CH.sub.2CH).sub.2CHOCO, (CH.sub.2CHCH.sub.2).sub.2CHOCO, (CH.sub.2CH).sub.2CHO, (CH.sub.2CHCH.sub.2).sub.2N, HOCW.sup.2W.sup.3, HSCW.sup.2W.sup.3, HW.sup.2N, HOCW.sup.2W.sup.3NH, CH.sub.2CW.sup.1CONH, CH.sub.2CH(COO).sub.k1-Phe-(O).sub.k2, Phe-CHCH, HOOC, OCN, with W.sup.1 being H, Cl, CN, phenyl or alkyl with 1 to 5 C atoms, W.sup.2 and W.sup.3 being independently of each other H or alkyl with 1 to 5 C atoms, Phe being 1,4-phenylene and k.sub.1 and k.sub.2 being independently of each other 0 or 1.

Description

EXAMPLES

[0359] In the Examples, [0360] V.sub.o denotes threshold voltage, capacitive [V] at 20 C., [0361] n.sub.e denotes extraordinary refractive index at 20 C. and 589 nm, [0362] n.sub.o denotes ordinary refractive index at 20 C. and 589 nm, [0363] n denotes optical anisotropy at 20 C. and 589 nm, [0364] .sub. denotes dielectric permittivity parallel to the director at 20 C. and 1 kHz, [0365] .sub. denotes dielectric permittivity perpendicular to the director at 20 C. and 1 kHz, [0366] denotes dielectric anisotropy at 20 C. and 1 kHz, [0367] cl.p., T(N,I) denotes clearing point [ C.], [0368] .sub.1 denotes rotational viscosity measured at 20 C. [mPa.Math.s], determined by the rotation method in a magnetic field, [0369] K.sub.1 denotes elastic constant, splay deformation at 20 C. [pN], [0370] K.sub.2 denotes elastic constant, twist deformation at 20 C. [pN], [0371] K.sub.3 denotes elastic constant, bend deformation at 20 C. [pN],

[0372] The term threshold voltage for the present invention relates to the capacitive threshold (V.sub.0), unless explicitly indicated otherwise. In the Examples, as is generally usual, the optical threshold can also be indicated for 10% relative contrast (V.sub.10), for 50% relative contrast (V.sub.50), and for 90% relative contrast (V.sub.90).

Preparation of Modified Polymer

Synthesis Example 1

[0373] The compound of interest is prepared according to the following Scheme:

##STR00240##

[0374] The compound is prepared based on a method known from the literature, see P. Martens, T. Holland, K. S. Anseth, Polymer 43 (2002), pp. 6093-6100. To a 40 ml anhydrous dichloromethane solution of the succinic acid mono-(2-acryloyloxy-ethyl) ester (3.59 ml; 20.43 mmol) N,N-dicyclohexylcarbodiimide (2.11 g; 10.21 mmol) is slowly added, while cooling at ice bath. After stirring at room temperature for 1 h under nitrogen, the precipitate is filtered off. The filtrate is evaporated, and the residue is dissolved in anhydrous DMSO (5 ml), and a solution of poly(vinyl alcohol) (M.sub.w 9,000-10,000, 80 mol % hydrolyzed) (9.00 g) in 50 ml dimethyl sulfoxide, which is prepared by heating at 60 C. for 1 h, is added at room temperature. Triethylamine (2.85 ml; 20.43 mmol) is added and the solution is stirred overnight at room temperature. The mixture is precipitated in 600 ml aceton:ether (1:1 ratio). The precipitate is collected and dried under reduced pressure overnight (8 g).

[0375] .sup.1H NMR (D.sub.2O): acrylate group; 6.37 ppm (d, J=17.8 Hz), 6.13 ppm (dd, J=11.5 Hz, J=17.8 Hz), 5.93 ppm (d, J=11.5 Hz)

Synthesis Example 2

[0376] The compound of interest is prepared according to the following Scheme:

##STR00241##

[0377] Anhydride of acrylic acid (1.47 g) is added to pre-dissolved Mowiol 4-88 (9.0 g) from Sigma-Aldrich (PVA, M.sub.w31,000 (in short 31 k), 88 mol % hydrolyzed) in 50 ml DMSO. The mixture is stirred overnight at room temperature. A filterable solid is obtained by adding to MeOH (300 ml), and precipitating is carried out by addition of ether (300 ml). The product is dried in vacuo at room temperature. 9.12 g of a yellow solid is obtained.

[0378] .sup.1H NMR (D.sub.2O): acrylate group; 6.36 ppm (d, J=17.6 Hz), 6.13 ppm (dd, J=10.69 Hz, J=17.6 Hz), 5.88 ppm (d, J=10.69 Hz)

Synthesis Example 3

[0379] The compound of interest is prepared according to the following Scheme:

##STR00242##

[0380] Anhydride of succinic acid mono(2-acyloyloxyethyl)ester (4.42 g) is added to pre-dissolved Mowiol 4-88 (9.0 g) from Sigma-Aldrich (PVA, M.sub.w31,000, 88 mol % hydrolyzed) in 50 ml DMSO. A filterable solid is obtained by adding to MeOH (300 ml), and precipitating is carried out by addition of ether (300 ml). The product is dried in vacuo at room temperature. 10.63 g of a solid is obtained.

[0381] .sup.1H NMR (D.sub.2O): acrylate group; 6.34 ppm (d, J=17.4 Hz), 6.09 ppm (dd, J=10.2 Hz, J=17.4 Hz), 5.88 ppm (d, J=10.2 Hz)

Synthesis Example 4

[0382] Anhydride of succinic acid mono(2-acyloyloxyethyl)ester (4.42 g) is added to pre-dissolved PVA (9.0 g) (M.sub.w9000-10000, 80 mol % hydrolyzed) in 50 ml DMSO. A filterable solid is obtained by adding to MeOH (300 ml), and precipitating is carried out by adding the reaction mixture to 375 ml of methanol:ether (1:2 ratio). The product is dried in vacuo at room temperature. 7.94 g of a solid is obtained.

[0383] .sup.1H NMR (D.sub.2O): acrylate group; 6.35 ppm (d, J=17.4 Hz), 6.08 ppm (dd, J=10.2 Hz, J=17.4 Hz), 5.89 ppm (d, J=10.2 Hz)

Synthesis Example 5

[0384] 4.5 g of PVA (M.sub.w9,000-10,000, 80 mol % hydrolyzed) is solubilized in 35 ml DMSO. The solution is added to 4.42 g of anhydride of mono (2-acyloyloxylethyl) succinate). The mixture is then stirred for 2 days. Methanol (40 ml) is added. Then ether (100 ml) is added slowly with vigorous stirring to produce a gum. The supernatant liquors are decanted and the solid is washed with 2:1 ether:methanol. The solid is redigested into DMSO (30 ml) over 5 minutes, then ether (100 ml) is added. The supernatant liquors are decanted and the residual solid is redissolved in methanol (20 ml) over 5 minutes. Ether (50 ml) is added. The supernatant liquors are decanted, washed with ether, then dried in vacuo at room temperature to give a pale yellow solid (6.13 g).

[0385] .sup.1H NMR (D.sub.2O): acrylate group; 6.38 ppm (d, J=17.4 Hz), 6.11 ppm (dd, J=11.5 Hz, J=17.4 Hz), 5.91 ppm (d, J=11.5 Hz)

Synthesis Example 6

[0386] 4.5 g of Mowiol 4-88 from Sigma-Aldrich (PVA, M.sub.w31,000, 88 mol % hydrolyzed) is solubilized in 35 ml DMSO. The solution is added to 4.42 g of anhydride of mono (2-acyloyloxylethyl) succinate). The mixture is stirred for 2 days. Methanol (40 ml) is added, then ether (100 ml) is added slowly with vigorous stirring to produce a solid. The crude product is partially redigested into methanol (50 ml) over 20 minutes forming a gelatinous slurry. Ether (60 ml) is added to give a cream-coloured particulate solid. The solid is filtered, washed with 1:1 methanol:ether and then ether to yield the product (5.08 g) as a tan-coloured solid after drying in vacuo at room temperature.

[0387] .sup.1H NMR (D.sub.2O): acrylate group; 6.35 ppm (d, J=17.6 Hz), 6.12 ppm (dd, J=11.4 Hz, J=17.6 Hz), 5.91 ppm (d, J=11.4 Hz)

Preparation of Nanocapsules

Reference Example 1

[0388] A liquid-crystal mixture B-1 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00007 Base Mixture B-1 CPGP-5-2 5.00% Clearing point [ C.]: 102.0 CPGP-5-3 5.00% n: 0.249 PGUQU-3-F 6.00% n.sub.e: 1.761 PGUQU-5-F 8.00% : 14.2 PGU-3-F 8.00% .sub.: 18.3 PUQU-3-F 17.00% K.sub.1 [pN]: 16.8 CP-3-O1 10.00% K.sub.3 [pN]: 16.8 PGIGI-3-F 6.00% .sub.1 [mPa .Math. s]: 282 PPTUI-3-2 10.00% V.sub.0 [V]: 1.13 PPTUI-3-4 15.00% PTP-1-O2 5.00% PTP-2-O1 5.00% 100.00%

[0389] LC mixture B-1 (1.00 g), hexadecane (175 mg), methyl methacrylate (100 mg), hydroxyethyl methacrylate (40 mg) and ethylene glycol dimethacrylate (300 mg) are weighed into a 250 ml tall beaker.

[0390] Brij L23 (50 mg) (from Sigma Aldrich) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated in an ultrasound bath for 10 minutes.

[0391] The Brij L23 aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.

[0392] The mixture is charged into a flask and fitted with a condenser, and after adding AIBN (35 mg) is heated to 70 C. for three hours. The reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.

[0393] The obtained capsules have an average size of 213 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).

[0394] The particle suspension is then concentrated by centrifugation, wherein the centrifuge tube is placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and then at 15,000 rpm for 20 minutes. The resulting pellet is redispersed in 1 ml of the supernatant.

Reference Example 2

[0395] A liquid-crystal mixture B-2 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00008 Base Mixture B-2 APUQU-3-F 8.00% Clearing point [ C.]: 128 CPU-3-F 15.00% n: 0.206 CCGU-3-F 8.00% n.sub.e: 1.711 CPGP-5-2 4.00% : 42.7 CPGP-5-3 4.00% .sub.: 48.2 CPGU-3-OT 8.00% DPGU-4-F 4.00% PGU-2-F 10.00% PGU-3-F 11.00% PGUQU-3-F 8.00% PGUQU-4-F 10.00% PGUQU-5-F 10.00% 100.00%

[0396] LC mixture B-2 (1.0 g), ethylene dimethacrylate (0.34 g), 2-hydroxy ethylmethacrylate (0.07 g) and hexadecane (0.25 g) are weighed into a 250 ml tall beaker.

[0397] This mixture is treated and investigated as described above in Reference Example 1.

Reference Example 3

[0398] A liquid-crystal mixture B-3 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00009 Base Mixture B-3 DGUQU-4-F 3.00% Clearing point [ C.]: 85.5 DPGU-4-F 2.00% n: 0.208 PGUQU-3-F 8.00% n.sub.e: 1.705 PGUQU-4-F 9.00% : 24.0 PGUQU-5-F 10.00% .sub.: 28.4 PGU-3-F 5.00% PPTUI-3-2 11.00% PPTUI-3-4 15.00% PUQU-3-F 13.00% CC-3-O1 15.00% CP-3-O1 9.00% 100.00%

[0399] LC mixture B-3 (2.00 g), methyl methacrylate (165 mg), hydroxyethyl methacrylate (75 mg) and ethylene glycol dimethacrylate (660 mg) are weighed into a 250 ml tall beaker.

[0400] Brij L23 (150 mg) is weighed into a 250 ml conical flask and water (150 g) is added. This mixture is then sonicated for 5 to 10 minutes.

[0401] The Brij L23 aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.

[0402] The mixture is charged into a flask and fitted with a condenser, and after adding AIBN (35 mg) is heated to 70 C. for three hours. The reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.

[0403] The obtained capsules have an average size of 167 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).

[0404] The particle suspension is then concentrated by centrifugation, wherein the centrifuge tube is placed in a centrifuge (ThermoFisher Biofuge Stratos) and centrifuged at 6,500 rpm for 10 minutes and at 15,000 rpm for 20 minutes. The resulting pellet is redispersed in 0.7 ml of the supernatant.

Reference Example 4

[0405] A liquid-crystal mixture B-4 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00010 Base Mixture B-4 CPGP-5-2 3.00% Clearing point [ C.]: 98.5 PUQU-3-F 15.00% n: 0.252 PGUQU-3-F 6.00% n.sub.e: 1.76 PGU-3-F 8.00% : 19.8 PGUQU-5-F 8.00% .sub.: 24.0 CP-3-O1 15.00% PPTUI-3-2 15.00% PPTUI-3-4 20.00% PTP-1-O2 5.00% GUUQU-3-N 5.00% 100.00%

[0406] LC mixture B-4 (2.00 g), hexadecane (100 mg), methyl methacrylate (100 mg), hydroxyethyl methacrylate (130 mg) and ethylene glycol dimethacrylate (198 mg) are weighed into a 250 ml tall beaker.

[0407] Brij L23 (300 mg) is weighed into a 250 ml conical flask and water (100 g) is added. This mixture is then sonicated for 5 to 10 minutes.

[0408] The Brij L23 aqueous surfactant solution is poured directly into the beaker containing the organics. The mixture is turrax mixed for 5 minutes at 10,000 rpm. Once turrax mixing is complete, the crude emulsion is passed through a high-pressure homogenizer at 30,000 psi four times.

[0409] The mixture is charged into a flask and fitted with a condenser, and after adding AIBA (20 mg) is heated to 70 C. for three hours. The reaction mixture is cooled, filtered, and then size analysis of the material is carried out on a Zetasizer (Malvern Zetasizer Nano ZS) instrument.

[0410] The obtained capsules have an average size of 129 nm, as determined by dynamic light scattering (DLS) analysis (Zetasizer).

Preparation of Binder

Comparative Example 1

[0411] Preparation of a 30% Solid Content PVA Binder

[0412] The PVA (molecular weight M.sub.w of PVA: 31 k; 88% hydrolysed) is first washed to remove ions in a Soxhlet apparatus for 3 days.

[0413] Deionized water (46.66 g) is added to a 150 ml bottle, a large magnetic stirrer bar is added and the bottle is placed on a 50 C. stirrer hotplate and allowed to come to temperature. 20.00 g of the solid washed 31 k PVA are weighed into a beaker. A vortex is created in the bottle and gradually the 31 k PVA is added over approximately 5 minutes, stopping to allow the floating PVA to disperse into the mixture. The hotplate is turned up to 90 C. and stirring is continued for 2-3 hours. The bottle is placed in oven at 80 C. for 20 hours. The mixture is filtered whilst still warm through a 50 m cloth filter under an air pressure of 0.5 bar. The filter is replaced with a Millipore 5 m SVPP filter and the filtration is repeated.

[0414] The solid content of the filtered binder is measured 3 times and the average is calculated by weighing an empty DSC pan using a DSC microbalance, adding approximately 40 mg of the binder mixture to the DSC pan and recording the mass, placing the pan on a 60 C. hotplate for 1 hour followed by 110 C. hotplate for 10 min, removing the pan from the hotplate and allowing to cool, recording the mass of the dry pan, and calculating the solid content.

Reference Examples 5, 6, 7, 8, 9 and 10

[0415] Preparation of 30% Solid Content Acrylate-Modified PVA Binders

[0416] The products of Synthesis Examples 1, 2, 3, 4, 5 and 6 are respectively dissolved in water to give 30% solutions of the respective modified PVA binders.

Preparation of Composite Systems

Comparative Example 2

[0417] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the PVA as prepared in Comparative Example 1, wherein the 30% washed 31 k PVA mixture is added in 2.5 ml vials, and then the nanocapsules are added to the vials. The weight ratio of PVA to capsules is 60:40. Deionized water is added to give a total solids content of 20%. The mixture is stirred using a vortex stirrer and leaving the mixture on a roller (Ratek RM5 Heavy Duty Roller) overnight to allow the PVA to disperse.

[0418] Film Preparation on Substrate

[0419] The substrate used is IPS (in-plane switching) glass having indium tin oxide (ITO) coated interdigitated electrodes with an electrode width of 4 m and a gap of 8 m. Prior to use the substrate is washed with deionised water and placed in a sonicator for 10 minutes, then washed with acetone, 2-propanol (IPA) and finally water for ion-chromatography. The substrate is then dried using a compressed air gun. The substrate is then treated with UV-ozone for 10 minutes.

[0420] The composite system comprising the nanocapsules and the binder are then coated on the substrate. 40 L of the mixture is coated as a film using a coating machine (K Control Coater, RK PrintCoat Instruments, bar coating with k bar 1, coating speed of 7). The sample is dried at 60 C. for 10 minutes on a hotplate. The appearance of the film is recorded. The prepared film is stored in a dry box between measurements.

[0421] Film thickness is measured by removing a small area of the film from above the electrical contacts with a razor blade. The film thickness is measured in the region of the middle electrode using a profilometer (Dektak XT surface profiler, Bruker) with a stylus force of 5 mg and a scan length of 3000 nm and a time of 30 s.

[0422] Measurement of Electro-Optical Properties

[0423] The appearance of the respective films is checked by eye for uniformity and defects. Wires are soldered onto the ITO electrodes of the substrate. Voltage-transmission curves are measured using a display measurement system (Autronic-Melchers DMS-301) with applying a field of 1 kHz.

[0424] Images of the dark and light state are also recorded using a microscope, in the absence of an electric field for the dark state and with an applied electric field at the required voltages for respectively 10% and 90% transmission.

[0425] Switching speeds are measured at 40 C. and 25 C. at 150 Hz modulation frequency, and also at 10 Hz as appropriate.

[0426] The measured electro-optical parameters for the prepared film comprising the nanocapsules and the binder are given in the following Table. In this Comparative Example and the following Examples hysteresis is determined at V.sub.50.

TABLE-US-00011 film thickness 3.8 m dark state transmission 1.17% bright state transmission 16.2% V.sub.90 30.5 V hysteresis 3.25 V

Working Example 1

[0427] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 5 containing the acrylate-modified PVA binder as prepared in Synthesis Example 1. The weight ratio of PVA to capsules is 60:40. To the mixture photoinitiator Irgacure 2959 (2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone, from Sigma-Aldrich) (5% by weight relative to the weight of the solid modified PVA polymer) is added.

[0428] The mixture is then treated and measured as described in Comparative Example 2.

[0429] After measuring the electro-optical properties of the prepared film, the film is cured using broad band UV light (UVACUBE 2000, Dr. Hnle AG) at 80 mW/cm.sup.2 with an exposure time of 3 minutes.

[0430] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Table.

TABLE-US-00012 before curing after curing film thickness 3.5 m dark state transmission 1.02% 0.28% bright state transmission 14.9% 8.4% V.sub.90 35.0 V 30.0 V hysteresis 4.75 V 0.50 V

[0431] Among other advantages, in particular an improved dark state and a reduced hysteresis are obtained.

Working Example 2

[0432] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 5 containing the acrylate-modified PVA binder as prepared in Synthesis Example 1. The weight ratio of PVA to capsules is 60:40. To the mixture photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from Sigma-Aldrich) (5% by weight relative to the weight of the solid modified PVA polymer) is added.

[0433] The mixture is then treated and measured as described in Comparative Example 2.

[0434] After measuring the electro-optical properties of the prepared film, the film is cured using broad band UV light (UVACUBE 2000, Dr. Hnle AG) at 80 mW/cm.sup.2 with an exposure time of 30 seconds.

[0435] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Table.

TABLE-US-00013 before curing after curing film thickness 2.8 m dark state transmission 0.32% 0.18% bright state transmission 11.1% 8.4% V.sub.90 33.0 V 36.0 V hysteresis 0.75 V 0.75 V

[0436] Among other advantages, in particular an improved dark state and a reduced hysteresis are obtained.

Working Example 3

[0437] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 5 containing the acrylate-modified PVA binder as prepared in Synthesis Example 1. The weight ratio of PVA to capsules is 60:40. To the mixture photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from Sigma-Aldrich) (5% by weight relative to the weight of the solid modified PVA polymer) is added.

[0438] The mixture is then treated and measured as described in Comparative Example 2.

[0439] After measuring the electro-optical properties of the prepared film, the film is cured using an LED (365 nm, 80 mW/cm.sup.2, Delolux) with an exposure time of 1 minutes.

[0440] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Table.

TABLE-US-00014 before curing after curing film thickness 2.9 m dark state transmission 0.3% 0.16% bright state transmission 11.2% 9.0% V.sub.90 35.0 V 40.0 V hysteresis 0.50 V 0.50 V

[0441] Among other advantages, in particular an improved dark state and a reduced hysteresis are obtained.

Working Example 4

[0442] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 5 containing the acrylate-modified PVA binder as prepared in Synthesis Example 1. The weight ratio of PVA to capsules is 60:40. To the mixture 5% by weight, relative to the solid weight of the binder, of initiator AIBN (2,2-azobis(2-methylpropionitrile), from Sigma-Aldrich) is added.

[0443] The mixture is then treated and measured as described in Comparative Example 2.

[0444] After measuring the electro-optical properties of the prepared film, the film is cured on a hotplate at 75 C. for 2 h under nitogen.

[0445] The measured electro-optical parameters for the prepared film before and after thermal curing are given in the following Table.

TABLE-US-00015 before curing after curing film thickness 3.3 m dark state transmission 0.96% 0.65% bright state transmission 16.3% 17.6% V.sub.90 34.5 V 37.5 V hysteresis 3.75 V 2.50 V

[0446] Among other advantages, in particular an improved dark state, a favourable bright state transmission and a reduced hysteresis are obtained.

Working Example 5

[0447] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 6 containing the acrylate-modified PVA binder as prepared in Synthesis Example 2. The weight ratio of PVA to capsules is 60:40. To the mixture 5% by weight, relative to the solid weight of the binder, of photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from Sigma-Aldrich) is added.

[0448] The mixture is then treated and measured as described in Comparative Example 2.

[0449] After measuring the electro-optical properties of the prepared film, the film is cured using an LED (Delolux from DELO, wavelength 365 nm) initially using an exposure time of 20 seconds at 60 mW/cm.sup.2, followed by an exposure at 80 mW/cm.sup.2 for 60 seconds.

[0450] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Tables.

TABLE-US-00016 before curing after curing film thickness 3.4 m dark state transmission 0.72% 0.41% bright state transmission 14.6% 12.1% V.sub.90 25.5 V 37.5 V hysteresis 0.75 V 0.50 V

[0451] Among other advantages, in particular an improved dark state and a reduced hysteresis and similar transmission are obtained.

Working Example 6

[0452] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 7 containing the acrylate-modified PVA binder as prepared in Synthesis Example 3. The weight ratio of PVA to capsules is 60:40. To the mixture 5% by weight, relative to the solid weight of the binder, of photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from Sigma-Aldrich) is added.

[0453] The mixture is then treated and measured as described in Comparative Example 2.

[0454] After measuring the electro-optical properties of the prepared film, the film is cured using an LED (Delolux from DELO, wavelength 365 nm) using an exposure at 80 mW/cm.sup.2 for 60 seconds.

[0455] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Table.

TABLE-US-00017 before curing after curing film thickness 3.8 m dark state transmission 0.47% 0.27% bright state transmission 9.4% 6.8% V.sub.90 27 V 34 V hysteresis 0.75 V 0.50 V

[0456] Among other advantages, in particular an improved dark state and a reduced hysteresis are obtained.

Working Example 7

[0457] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 8 containing the acrylate-modified PVA binder as prepared in Synthesis Example 4. The weight ratio of PVA to capsules is 60:40. To the mixture 5% by weight, relative to the solid weight of the binder, of photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from Sigma-Aldrich) is added.

[0458] The mixture is then treated and measured as described in Comparative Example 2.

[0459] After measuring the electro-optical properties of the prepared film, the film is cured using an LED (Delolux from DELO, wavelength 365 nm) using an exposure at 80 mW/cm.sup.2 for 60 seconds.

[0460] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Table.

TABLE-US-00018 before curing after curing film thickness 3.0 m dark state transmission 0.3% 0.15% bright state transmission 6.8% 5.8% V.sub.90 29 V 21 V hysteresis 0.75 V 0.50 V

[0461] Among other advantages, in particular an improved dark state and a reduced hysteresis are obtained.

Working Example 8

[0462] A concentrated nanocapsule sample as prepared in Reference Example 1 is added to the binder formulation as prepared in Reference Example 10 containing the acrylate-modified PVA binder as prepared in Synthesis Example 6. The weight ratio of PVA to capsules is 60:40. To the mixture 5% by weight, relative to the solid weight of the binder, of photoinitiator TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from Sigma-Aldrich) is added.

[0463] The mixture is then treated and measured as described in Comparative Example 2.

[0464] After measuring the electro-optical properties of the prepared film, the film is cured using an LED (Delolux from DELO, wavelength 365 nm) initially using an exposure time of 3 seconds at 80 mW/cm.sup.2, followed by an exposure at 60 mW/cm.sup.2 for 30 seconds.

[0465] The measured electro-optical parameters for the prepared film before and after curing with UV light are given in the following Table.

TABLE-US-00019 before curing after curing film thickness 3.4 m dark state transmission 0.73% 0.34% bright state transmission 14.7% 15.8% V.sub.90 34 V 44.5 V hysteresis 1.25 V 1.25 V

[0466] Among other advantages, in particular an improved dark state is obtained.

Working Examples 9, 10 and 11

[0467] Concentrated nanocapsule samples as prepared respectively in Reference Example 2, Reference Example 3 and Reference Example 4 are respectively added to the binder formulation as prepared in Reference Example 5 containing the acrylate-modified PVA binder as prepared in Synthesis Example 1. The mixtures are then treated as further described in Working Example 4.

[0468] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0469] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.