Synthesis and properties of copolyesters having an ordered comonomer sequence: copolyesters prepared from naphthylene bis(4-hydroxybenzoate)s and α,ω-bis(4-carboxyphenoxy)alkanes

Abstract

A series of sequentially ordered copolyesters were prepared from isomeric naphthylene bis(4-hydroxybenzoate)s (NBHBs) and α,ω-bis(4-carboxyphenoxy)alkanes (BCPAs) with varying length of α,ω-alkylene units. All of the copolyesters were composed of naphthalenediol (NAPH), BCPA and p-hydroxybenzoic acid (POB) (1:1:2 molar ratio). The polymer chains were made up of POBNAPHPOBBCPA segments. The naphthalene units were derived from 1,5-, 1,6-, 2,6- and 2,7-naphthalenediols. The BCPAs employed were 1,4-butane, 1,5-pentane and 1,10-decane derivatives. The melting points and crystallizability of these copolyesters were found to be much higher than those of the corresponding random copolyesters having the same overall compositions. All of the polymers, with the exception of the polyester derived from 2,7-naphthalenediol and 1,5-pentane spacers, formed nematic phases in melts. The ordered sequence copolyesters were found to undergo a rapid sequence randomization at temperatures higher than their melting points. A model compound of a copolyester, 2,7-naphthylene bis[4-(4-n-butoxybenzoyloxy)-benzoate], was also synthesized and its thermal behaviour and liquid crystal properties were studied.