Lyotropic Liquid Crystalline Polyamides Containing Aromatic, Heterocyclic Structures: Preparation and Properties

Abstract

A series of novel lyotropic liquid crystalline polyamides derived from l,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)]-phthalazinone (DHPZ-DA), p-phenylene diamine (PPD) and terephthaloyl dichloride (TPC) have been successfully synthesized by the low temperature solution polycondensation method. The copolymers obtained with inherent viscosity of ≈1.21 to 3.29 dl·g -1 , determined in NMP (1 wt.-% LiCI) or concentrated H 2 SO 4 at 25°C, were confirmed to be amorphous by WAXD and differential scanning calorimetry (DSC). Their solubility was improved by the introduction of non-coplanar, twisted phthalazinone moieties and ether linkages into the main chain with the result that they can be soluble in some polar solvents containing a small amount of LiCI. Their T g s were all above 310°C and 10% weight loss temperatures in nitrogen above 500°C. Most of these polyamides can form an anisotropic phase in concentrated H 2 SO 4 , NMP (1 wt.-% LiCI) and DMAc (1 wt.-% LiCI) solutions, observed on a polarizing light microscope.