Properties of polymer liquid crystals: choosing molecular structures and blending

Liquid crystalline polyimides: 18. Thermotropic polyimides based on biphenyl-3,3′,4,4′-tetracarboxylic anhydride

LC-polyimides: 5. Poly(ester-imide)s derived from N-(4-carboxyphenyl) trimellitimide and α,ω-dihydroxyalkanes

Poly(ester-imide)s with a regular sequence of aliphatic spacers and aromatic imide mesogens were prepared in two ways. Either aliphatic α,ω-diacids were condensed with an acetylated diphenol derived from 4-hydroxyphthalic acid and 4-aminophenol, or aliphatic α,ω-diacid dichlorides were condensed with the silylated diphenol. The resulting poly(ester-imide)s were characterized by elemental analyses, viscosity measurements, microscopy under polarized light, DSC- and WAXS measurements. All poly(ester-imide)s are crystalline materials with a layered supermolecular structure in the solid state. Above the melting point a nematic mesophase exists over a broad temperature range. A pronounced odd-even effect was found for the temperature of isotropization, but not for the melting points.

Liquid-crystalline polyimides, 1. Thermotropic poly(ester-imide)s derived from 4-hydroxyphthalic acid, 4-aminophenol and various aliphatic α,ω-diacids

The present review reports on structure-property relationships of LC-main chain polymers containing imide groups. The comments focus on the role of aromatic imide moieties as mesogenic building blocks. All the pertinent literature has been cited. This review is subdivided into six sections dealing: A) with fundamental stereochemical and conformational aspects of aromatic imide groups, B) with structure-property relationships of fully aromatic poly(ester-imide), C) with the properties of LC-poly(ester-imide)s containing regular sequences of aromatic and aliphatic building blocks, D) with synthesis and characterization of cholesteric poly(ester-imide)s, E) with structures and properties of LC-polyimides free of ester groups, and F) with the definition and characterization of layer structures in the solid state regardeless whether the pertinent polyimides form a true LC-phase or not.

Liquid-crystalline polyimides

Synthese d'homopolyesters avec des temperatures de distorsion thermique superieures a 150°C et thermiquement stables jusqu'a 350°C

New polymer syntheses. 20. Liquid-crystalline poly(ester imides) derived from trimellitic acid, .alpha.,.omega.-diaminoalkanes, and 4,4'-dihydroxybiphenyl

New polymer syntheses: 21. LC-poly(ester imide)s prepared from trimellitic acid, α,θ-diaminoalkanes and various hydroquinones or dihydroxynaphthalenes

New polymer syntheses. 24. Liquid crystal poly(ester imides) derived from benzophenonetetracarboxylic dianhydride and .omega.-amino acids

Diacids with variable spacer length were prepared by condensation of trimellitic anhydride and ω-amino acids. From these diacids, homopolyesters were prepared by thermal condensation with the acetates of hydroquinone or 4,4′-dihydroxy biphenyl and a series of copolyesters containing 4-hydroxy benzoic acid. The same LC poly(ester imide)s could also be prepared in a “one-pot procedure” from trimellitic anhydrid, lactams, and bisphenol acetates. The differential scanning calorimetry (DSC) traces of most poly(ester imide)s exhibit two endotherms representing the solid → LC phase transition (Tm1) and the LC phase → isotropic melt transition (Tm2). Observation under the polarizing microscope and wide-angle X-ray scattering (WAXS) measurements suggest that the LC phase formed immediately above the melting points (Tm1) have a smectic character. Poly(ester imide)s of 4,4′-dihydroxybiphenyl possess higher melting points and a broader temperature range of the LC phase than those of hydroquinone. The copolyesters possess a nematic melt over a broad temperature range. Thermomechanical analyses under low pressure (0.05 kg/mm2) gave heat distortion temperatures close to the melting points (Tm1), and under high pressure (1 kg/mm2), values between Tm1 and the glass transition temperatures (Tg). Thermogravimetric measurements indicate that processing from the melt is feasible up to temperatures around 340°C.

New polymer syntheses 22. LC‐poly(esterimide)s derived from trimellitic acid, ω‐amino acids and hydroquinone or 4,4′‐dihydroxybiphenyl

Six dicarboxylic acids were prepared from pyromellitic dianhydride and ω-amino acids, such as glycine, 4-aminobutyric acid, 5-aminopentanoic acid, 6-aminohexanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid. Polyesters were prepared from these dicarboxylic acids and 4,4′-biphenyldiol, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, methyl-, chloro-and phenylhydroquinone. All polyesters were characterized by elemental analyses, viscosity and differential scanning calorimetry (DSC) measurements, and by optical microscopy. Several polyesters were also characterized by wide-angle X-ray scattering (WAXS) powder patterns, by penetration measurements and thermogravimetrical analyses. Those polyesters derived from highly symmetrical diphenols and diols are highly crystalline (>90%) and form a layer structure in the solid state. An amorphous phase was not detectable and the heat distortion temperature corresponds to the melting point. Poly(ester-imide)s derived from less symmetric diphenols are semicrystalline and glass transition temperatures are detectable. However, true liquid-crystalline phases were never found.

LC‐polyimides, 10. Poly(ester‐imide)s derived from pyromellitic dianhydride and ω‐amino acids and various diphenols or α,ω‐diols

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