Structure and properties of aromatic liquid crystalline polyesteramide

Abstract

Several series of polyesteramides such as homopolymers, ABHQ copolymers and ABP copolymers with ester and amide groups in a main chain were prepared by solution polymerization and their thermal, optical, rheological and mechanical properties were investigated by differential scanning calorimetry, cross polarizing light microscope, rheometrics dynamic spectrometer, scanning electron microscope and tensile tester. Since the polymers are degraded by losing 5% weight over 380℃ it can be said that they have a thermal stability. The melting transition of polymers with p-phenylene ring between two amide or ester groups was not observed over 310℃ because of the molecular rigidity and high melting temperature but other polymers exhibited endothermic peaks of melting transition by DSC scans. When the total number of repeating methylene units in a main chain such as propylene are odd, polyesteramides showed thermotropic behaviors. Most polymers were found smectic but some polymers such as ABPHQ-φφ-6, ABPHQ-φφ-8 and ABP(50/50) nematic. All polymers were soluble in 100% sulfuric acid. Only some of them such as ABP-3-φ, ABH-6-φ and ABHQ-copolymers showed a lyotropic liquid crystalline phase. The series of ABHQ copolymer solution were nematic and showed a wider nematic region with the portion of amide groups in a main chain because the chain rigidity became higher and the polymer-solvent interaction stronger. ABP-3-φ and ABH-6-φ polymer solutions with aliphatic flexible units between ester groups formed an anisotropic phase but ABHQ-φ-6 polymer with p-phenylene group between ester groups and six methylene units between amide groups did not show an anisotropy. Specially, the ABP-3-φ solution showed a smectic phase and ABH-6-φ turned out to be shear-induced lyotropic polymer. It was recognized from a series of experiments that the liquid crystalline phase of polyesteramide appeared at higher concentration and the potentiality of an anisotropy gradually decreased when aliphatic...