Soluble para-linked aromatic polyamides with pendent groups

Abstract

A series of para-linked aromatic polyamides having inherent viscosity of 0.51？0.91 dL/g were prepared from 2-trifluoromethyl-4,4′-diaminodiphenyl ether, 2-cyano-4,4′-diaminodiphenyl ether, 2-trifluoromethyl-4,4′- diaminodiphenyl sulfide, and 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl sulfide. The structure of the polyamides was confirmed with FTIR, 1H NMR, and 13C NMR spectroscopy. The polyamides containing trifluoromethyl or cyano pendent groups were soluble in polar aprotic solvents while the corresponding polyamides without pendent groups showed limited solubility, requiring LiCl in NMP even though they had flexible ether or thioether linkages. The polymers showed good thermal stability over 400 °C both in N2 and air, and they had a high glass transition or melting temperature. All of the synthesized polyamides have low refractive indices (n) in the range of 1.6164 to 1.6613 and low birefringence (Δ) in the range of 0.0101 to 0.0305 with slightly higher nxy than nz, indicating that the polyamides films are slightly anisotropic.[Figure not available: see fulltext.]