Synthesis and characterization of a series of thermotropic liquid crystalline copolyester nanocomposites

Abstract

A series of aromatic thermotropic liquid crystalline copolyester (TLCP) nanocomposites were prepared by the in situ intercalation polymerization of p-acetoxybenzoic acid (ABA), terephthalic acid (TPA), and diacetoxynaphthalene (DAN) isomers in the presence of the organoclay. The DAN isomers used in this study were 2,3- and 2,7-naphthylene. We examined the variation of the liquid crystallinity, morphology, and thermal properties of the nanocomposites with organoclay content in the range 0-10 wt %. All the polymer nanocomposites were fabricated with a molar ratio of ABA:TPA:DAN = 2:1:1; they were shown to consist of a nematic liquid crystalline phase for low organoclay contents (<= 5 wt %), whereas the hybrids with a higher concentration of organoclay (>= 10 wt %) were found not to be mesomorphic. By using transmission electron microscopy, the clay layers in the 2,3-DAN copolyester hybrids were found to be better dispersed in the matrix polymer than those in the 2,7-DAN copolyester hybrids. The introduction of an organoclay into the matrix polymer was found to improve the thermal properties of the 2,3-DAN copolyester hybrids. However, the thermal properties of the 2,7-DAN copolyester hybrids were found to be worse than those of the pure matrix polymer for all organoclay compositions tested. (c) 2005 Wiley Periodicals, Inc.