New soluble aromatic polyamides containing ether linkages and laterally attached p-terphenyls

Two series of new polyamides containing flexible ether linkages and laterally attached side rods (3a-i and 4a-i) were synthesized from 2′,5′-bis(4-aminophenoxy)-[1,1′;4′,1″]terphenyl (1a) and 2′,5′-bis(4-amino-2-trifluoromethylphenoxy)-[1,1′;4′,1″]terphenyl (1b), respectively, with various aromatic dicarboxylic acids by the direct phosphorylation polycondensation. The polymers were produced with high yields and moderate to high inherent viscosities (0.41–0.97 dl/g) that corresponded to weight-average molecular weights (by size exclusion chromatography) of 47,000–65,000. Except for some polyamides that derived from rigid diacids, the obtained polyamides were readily soluble in aprotic polar solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc), and could afford flexible and tough films via solvent casting. The polymer films cast from DMAc solutions possessed tensile strengths of 85–106 MPa and initial moduli of 1.82–2.96 GPa. These polyamides showed glass-transition temperatures (Tg) in the range of 206–263 °C (by DSC) and softening temperatures (Ts) in the range of 211–253 °C (by TMA). Decomposition temperatures (Td) for 10% weight loss all occurred above 400 °C (by TGA) in both nitrogen and air atmospheres. The polyamides 4a-i derived from trifluoromethyl-substituted diamine 1b generally showed a higher solubility, Tg and Ts but lower thermal stability as compared to the analogous polyamides 3a-i based on diamine 1a.