Two dicarboxylic acids were prepared by alkylation of 4-hydroxycinammic acid with 1,6-dibromohexane or 1,12-dibromododecane. The dichlorides of these dicarboxylic acids were polycondensed with mixtures of isosorbide and methylhydroquinone. All copolyesters then obtained showed nematic schlieren textures. Furthermore, three dicarboxylic acids were synthezised by alkylation of 4-hydroxycinammic acid with the ditosylates of di-, tri-, and tetraethylene glycol. Numerous copolyesters were prepared from the dicarboxylic acids and mixtures of isosorbide with methyl-, tert-butyl-, or phenylhydroquinone. Also 2,7-dihydroxynaphthalene was used as a comonomer. Almost all resulting copolyesters were cholesteric, and nearly 50% of them were capable of forming a Grandjean texture. The photochemical behavior of selected copolyesters was studied in solution in spin-coated films and in films with Grandjean texture. Depending on the reaction conditions, photo-cross-linking by 2 + 2 cycloaddition competed more or less successfully with the photo-Fries rearrangement and with the photoisomerization. UV irradiation (at 313 nm) of oriented films in the cholesteric melt caused disappearance of the Grandjean texture. However, irradiation below the glass-transition temperature caused stabilization of the Grandjean texture by photo-cross-linking.

SUMMARY Twenty four cholesteric and telechelic oligoesters were prepared having two maleimide or nadimide end groups. All oligoesters were synthesized by copolycondensation of isosorbide and methyl-or tertbutylhydroquinone with suitable dicarboxylic acid chlorides in 1 -chloronaphthalene at 200 "C. 4Maleimido-phenol or 4-nadimidophenol was added as terminating reagent. The isolated oligoesters had inherent viscosities in the range of 0,14-0,20 dl/g (CH$&/trifluoroacetic acid) and the presence of the imide end groups was confirmed by 'H and 13C NMR spectroscopy. Most oligoesters were non-crystalline materials with glass transition temperatures in the range of 105 130°C. Most oligoesters were capable of forming a Grandjean texture upon shearing of the cholesteric melt, and thermal crosslinking in the LC phase was possible upon heating to 250 "C. In several cases the thermal curve allowed a fixation of the Grandjean texture.

Numerous cholesteric copoly(ester-imide)s were prepared by polycondensation of N-(4-carboxyphenyl)trimellitimide (in the form of the dichloride) with isosorbide and various diphenols. 1, 6-hexanediol was incorporated as a flexibilizing component in various molar ratios. In two cases 1, 1′-decanediol was used. All copoly(ester-imide)s proved to be non-crystalline materials with glass transition temperatures ( Tgs) between 110 and 180 °C and a broad cholesteric melt. Most copoly(ester-imide)s derived from substituted hydroquinones were capable of forming a Grandjean texture upon shearing and of fixing the Grandjean texture upon cooling below Tg. However, 2, 7-dihydroxynaphthalene proved to be unfavourable for the formation of a Grandjean texture.

Numerous cholesteric copoly(ester-imide)s were prepared from mixtures of isosorbide and tert.-buthylhydroquinone (or other diphenols), on the one hand, and mixtures of adipoylchloride and N-(4-chlorocarbonylphenyl) trimellitimide chloride on the other. When the molar ratio of isosorbide/diphenol was varied, Grandjean textures were only observed for low concentrations of isosorbide (5/95 or 10/90). In the case of adipoylchloride/imide dichloride molar ratios of 30/70–50/50 favoured the formation of Grandjean textures. Most copoly(esterimide)s were non-crystalline with glass transition temperatures ( Tgs) between 90 and 190 °C. In several cases the Grandjean textures were frozen in by cooling below Tg. Such copoly(esterimide)s may be useful as pigments. All copoly(ester-imide)s containing methylhydroquinone were semicrystalline with melting temperatures in the range of 240–270 °C.

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