Synthesis and Properties of Thermotropic Copolyesters Based on Poly(ethylene terephthalate) and 4'-Acetoxy-4-biphenyl-carboxylic Acid.

Pavel A Mikhaylov,Boris Kh Strelets,Marina P Filatova,Valery G Kulichikhin,Kirill V Zuev

doi:10.3390/polym13111720

Pavel A Mikhaylov, Boris Kh Strelets + Show 3 more

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https://doi.org/10.3390/polym13111720

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Abstract

A series of novel copolyesters based on polyethylene terephthalate (PET) and 4′-hydroxy-biphenyl-4-carboxylic acid (HBCA) was obtained by melt polycondensation of bis(2-hydroxyethyl) terephthalate and 4′-acetoxybiphenyl-4-carboxylic acid (ABCA) as co-monomers with Sb2O3 as a catalyst. Using this synthetic procedure, a set of copolymers containing 20–80 mol% of HBCA units was prepared. According to NMR spectroscopy, the copolymers were of random composition. Copolyesters comprising 60–80 mol% of HBCA possessed increased heat resistance and formed nematic melts at 270 °C and higher. The liquid crystal (LC) phase formation was accompanied by transition to non-Newtonian characteristics of the melt flow, as well as an equalization of storage and loss moduli values. According to XRD and polarizing microscopy, the LC glassy phase of the copolyesters coexists with crystalline regions of poly-(4′-hydroxy-4-biphenylcarboxylate), non-melting up to 400 °C and above. The mechanical characteristics of these LC copolyesters showed similar or better values than those of well-known LC polymers. These novel copolyesters can be useful in obtaining heat-resistant materials with an ordered structure and, as a consequence, improved performance.

Highlights

The route for the synthesis of polyethylene terephthalate (PET)/hydroxybiphenyl-4-carboxylic acid (HBCA) copolyesters is shown in Scheme 1
A series of new copolyesters of PET and 40 -hydroxy-4-biphenylcarboxylic acid containing 20–80 mol% of HBCA units was successfully synthesized by melt polycondensation
Introduction of 60 mol% and more HBCA resulted in the production of copolyesters forming in melts the liquid crystal (LC) phase beginning with 270 ◦ C

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Among the wide range of melt-processed polymers, polyethylene terephthalate (PET). Is one of the most important large-scale polyesters due to a number of valuable characteristics: relative cheapness, excellent mechanical properties, chemical resistance, and so on [1]. PET processing can be difficult because of a high rate of crystallization and limited heat resistance characterized by a low glass transition point. The thermal and mechanical properties of PET can be improved by physical and chemical modifications:. (1) mixing with other polymers and (2) copolymerization [2].

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