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Glass transitions of thermotropic aromatic copolyesters
Author(s) -
Bensaad Salima,
Noël Claudine
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980801)199:8<1501::aid-macp1501>3.0.co;2-l
Subject(s) - thermotropic crystal , differential scanning calorimetry , glass transition , annealing (glass) , amorphous solid , materials science , nucleation , liquid crystal , polymer chemistry , isophthalic acid , crystallography , terephthalic acid , polymer , chemical engineering , chemistry , organic chemistry , polyester , composite material , thermodynamics , liquid crystalline , physics , optoelectronics , engineering
Abstract Three thermotropic copolyesters consisting of terephthalic acid (TA), p ‐hydroxybenzoic acid (HBA), 4,4′‐oxydibenzoic acid (OBBA) and methylhydroquinone (MH), and two copolyesters made from HBA, isophthalic acid (IA) and p ‐hydroquinone (H) were investigated by differential scanning calorimetry and optical microscopy. Amorphous isotropic samples were obtained either by rapid precipitation or by film casting. For all investigated polymers, the glass transition temperature in the nematic state ( T gN ) was found to be higher than that of samples in the isotropic state ( T gl ). Annealing of initially amorphous isotropic samples at temperatures above T gl resulted in the systematic development of order. The ordering process does not seem to be restricted to ordered nucleation sites which grow to encompass the whole sample, but appears rather global, the chains ordering more or less uniformly throughout the sample.