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Effect of the thermal history on the phase transition and the liquid crystalline structure of thermotropic polyesters
Author(s) -
Lee Young Jun,
Kim Sung Chul
Publication year - 1994
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1994.220050703
Subject(s) - thermotropic crystal , polyester , materials science , phase transition , liquid crystal , annealing (glass) , texture (cosmology) , polymer , crystallography , chemical engineering , composite material , liquid crystalline , thermodynamics , chemistry , physics , image (mathematics) , optoelectronics , artificial intelligence , computer science , engineering
A series of triad type thermotropic polyesters based on phenylsulfonyl hydroquinone and α,ω‐bis(4‐carboxyphenoxy)alkane was prepared, and the effect of the thermal history on the phase transition and the liquid crystalline structure of the polyesters was studied. The phase transition was significantly affected by the thermal history. When annealed at various temperatures, multiple endotherms were observed for all polyesters in DSC thermograms. A phase stability concept was employed to explain the complicated phase transitions. The time evolution of the liquid crystalline structure was investigated by optical microscopy and transmitted light intensity measurement under crossed polars during annealing. The steady decrease in the density of disclinations with accompanying increase of transmitted light intensity was observed. Depending on the surface conditions of the liquid crystal polymer film, two markedly different domain growth patterns and different textures were found on isothermal annealing; the continuous wormlike texture and the discontinuous droplet texture. The structural relaxation of the deformed texture during annealing was also studied. When shear was applied, the characteristic banded texture was formed in all polyesters.