Synthesis and characterization of liquid crystalline poly(ether-ketone)s containing 1-benzyl-4-piperidone moiety as a pendent group

Abstract

A series of poly(ether-ketone)s (PEKs) having 1-benzy-4-piperidone moiety as a pendant group was successfully synthesized from 3,5-bis(3-ethoxy-4-hydroxybenzyldehyde)-1-benzyl-4-piperidone and various dibromoalkanes employing solution polycondensation method. The structures of the novel monomer, model compound, and PEKs were characterized using FT-IR, 1H NMR, and mass Spectroscopy. The thermal and liquid crystalline properties of the synthesized polymers were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The study revealed that all of the prepared polymers are thermally stable. The glass transition temperature, Tg, was in the range of 46–117 °C, and the temperature that caused a 5% weight loss was over 290 °C. DSC profiles of PEKs with aliphatic spacer lengths 4 and 8 revealed both melting transition, Tm, and isotropization transition, Ti, peaks. These results indicate that the polymers possess a thermotropic liquid crystal structure. An optical microscopy study called polarized optical microscopy (POM) confirmed that these polymers have features of liquid crystals. Threaded and droplet textures could be seen under POM.