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Melting Behavior of a Wholly Aromatic Liquid Crystalline Random Copolyester
Author(s) -
Bensaad Salima,
Noël Claudine
Publication year - 2001
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 - 10.1002/1521-3935(20010101)202:1<36::aid-macp36>3.0.co;2-u
Subject(s) - copolyester , crystallization , differential scanning calorimetry , thermotropic crystal , terephthalic acid , melting point , isothermal process , materials science , thermodynamics , crystallography , kinetics , polymer chemistry , chemistry , organic chemistry , polymer , polyester , liquid crystalline , composite material , physics , quantum mechanics
Abstract Differential scanning calorimetry and wide‐angle X‐ray diffraction studies were carried out to investigate nonisothermal and isothermal crystallization of a thermotropic liquid crystalline copolyester consisting of terephthalic acid (TA), p ‐hydroxybenzoic acid (HBA), 4,4′‐oxydibenzoic acid (OBBA) and methylhydroquinone (MH) with mole ratios 19.2/23.1/19.2/38.5. Different crystallization processes are observed depending on crystallization conditions (cooling rate, crystallization temperature, crystallization time). Each of these processes is associated with a different melting point, heat of transition and kinetics of crystallization. The equilibrium thermodynamic properties of the process III (nonisothermal experiments at a cooling rate below 5°C/min or isothermal experiments in the temperature region above ca. 260°C) are found to be T m 0 = 352°C, Δ H 0 = 10.4 kJ·mol –1 , and Δ S 0 = 17 J·mol –1 ·K –1 . This process is associated with (TA/OBBA‐MH) sequences which contain the “swivel” OBBA units.