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Aromatic liquid-crystalline polyesters comprising a 2,5-thiophene unit synthesized and studied by the thin-film polymerization method

Published online by Cambridge University Press:  31 January 2011

Jingmei Xu
Affiliation:
Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602
Yan Wang
Affiliation:
Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602, and Department of Chemistry, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
Tai-Shung Chung*
Affiliation:
Department of Chemical and Environmental Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
Suat Hong Goh
Affiliation:
Department of Chemistry, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

A series of novel liquid-crystalline polymer (LCP) systems, including a heterocyclic 2,5-thiophene unit, were synthesized and studied using a modified thin-film polymerization method as part of a continuing investigation of molecular structural effects on liquid crystallinity. The monomers used in the reaction included p-acetoxybenzoic acid (ABA)/2,6-acetoxynaphtholic acid (ANA), 4,4′-biphenol (BP)/4,4′-diacetoxybiphenyl (DABP)/p-acetoxyacetanilide (AAA), and 2,5-thiophenedicarboxylic acid (TDA). Polarizing light microscopy and Fourier transform infrared spectra were used to study, in situ record the evolution of morphological change in the thin-film polymerization process, and confirm the occurrence of polymerization. Experimental results indicated that monomer structure and composition as well as temperature influence the formation of the liquid crystalline (LC) phase greatly and revealed that 2,5-thiophene structure is a viable mesogenic core unit. It is more effective than isophthalic acid (IA) in assisting in the LC formation as polymers containing TDA have a better developed LC phase and lower critical ABA content than those with IA. Stripe texture was observed in the ANA/DABP/TDA system, possibly due to the structural characteristics and matching of the monomers. The decrease of isotropic round areas in the LC phase and the annihilation between two pairs of defects with reaction time were also studied.

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Articles
Copyright
Copyright © Materials Research Society 2003

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