Preparation of polyamides containing para-linked dimethylbiphenylene moieties

A series of wholly aromatic polyamides containing 3,3′-dimethylbiphenyl-4,4′-dicarboxylic acid (P-DMBA) and 3,4′-dimethylbiphenyl-4,3′-dicarboxylic acid (Q-DMBA) was prepared by the direct polycondensation method using triphenylphosphite and pyridine. Most of the polymers are readily soluble in polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), N,N′-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), pyridine (py), and m-cresol and could be cast into tough and flexible films. The solubilities of copolyamides containing P-DMBA and Q-DMBA as acid components were remarkably improved. These were characterized by inherent viscosity, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical spectrometry (DMS) measurements. The glass transition temperatures of these polymers were in the range of 200–300°C and the 5% weight loss temperatures were 430–470°C. Films prepared by casting from polymer solutions exhibited good tensile properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:847–853, 1998