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Thermotropic copolyesters of 4‐hydroxybenzoic acid
Author(s) -
Kricheldorf Hans R.,
Conradi Arnd,
Pakull Ralf,
Schwarz Gert
Publication year - 1989
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19890260105
Subject(s) - thermotropic crystal , hydroxybenzoic acid , liquid crystal , condensation polymer , polymer chemistry , chemistry , glass transition , phase (matter) , materials science , hydroxybenzoate , organic chemistry , polymer , liquid crystalline , optoelectronics
Copolyesters of 4‐hydroxybenzoic acid were prepared by thermal polycondensation of 4‐acetoxybenzoic acid with various acetylated comonomers, such as 4‐mercaptobenzoic acid, 3‐hydroxybenzoic acid, N‐(4‐carboxyphenyl)4‐hydroxyphthalimide or hydroquinone in combination with 1,12‐dodecane bistrimellitimide. The copolyesters were characterized by elemental analyses, inherent viscosities, 1 H‐ or 13 C NMR spectroscopy, DSC‐measurements, WAXS‐measurements at temperatures between 25 and 425°C, microscopic observation, thermomechanical and thermogravimetrical analyses. Copolyesters containing 4‐mercaptobenzoic acid or N‐(4‐carboxyphenyl)4‐hydroxyphthalimide possess a reversible first order phase transition which represent a change of modifications and not a melting process. Both classes of copolyesters adopt the same kind of high temperature modification as poly(4‐hydroxybenzoate), namely a pseudo‐hexagonal chain packing. In contrast, copolyesters of 3‐hydroxybenzoic acid or copoly(ester imide)s with aliphatic spacer containing more than 50% 4‐hydroxybenzoic acid form a nematic phase over a broad temperature range. However, in the case of copolyesters derived from 3‐ and 4‐hydroxybenzoic acid the homogeneous nematic melt is thermodynamically unstable and gradually turns into a heterogeneous more or less crystalline material with blocks of 4‐hydroxybenzoate units.