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Comparison of the properties of thermotropic liquid crystalline copolyesters containing different disymmetrical units
Author(s) -
Kim H. D.,
Paul D. R.
Publication year - 1990
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1990.070410739
Subject(s) - thermotropic crystal , copolyester , materials science , hydroquinone , ethylene , hydroxybenzoic acid , glass transition , polymer chemistry , polymer , liquid crystalline , chemical engineering , composite material , polyester , organic chemistry , chemistry , catalysis , engineering
The effect of dissymetrical units on the properties of thermotropic liquid crystalline copolyesters based on hydroxybenzoic acid (HBA), terephthalate) acid (TPA), and poly(ethylene terephthalate) (PET) units was examined. The dissymmetrical units employed included 2,7‐dihydroxynaphthalene (2,7‐DHN),1,4‐dihydroxynaphthalene (1,4‐DHN), and bromo‐hydroquinone (Br‐HQ). All of these polymers exhibited turbid melts. The flexible PET units lower the melting and/or stick temperature, and between 10 to 20 mol % is a critical level to achieve values in the range of 250°C or lower. The copolyesters based on 2,7‐DHN have the highest glass transition temperatures and maintain stiffness to the highest temperatures. The properties of each series of copolyesters are discussed in terms of the efficiency of molecular packing. The effects of chemical and physical inhomogeneity are emphasized.