Rigid‐Rod Polyamides from 3,3′‐bis­(trifluoromethyl)‐4,4′‐diamino‐1,1′‐biphenyl

Abstract

A diamine monomer with trifluoromethyl groups, 3,3′‐bis(trifluoromethyl)‐4,4′‐diamino‐1,1′‐biphenyl, is synthesized from 5‐bromo‐2‐nitrobenzotrifluoride with two steps. The model reaction with monofunctional benzoyl chloride at room temperature gives the model compound with a quantitative yield. The results of the model reaction indicate that the amine groups have sufficient reactivity in spite of the presence of electron‐withdrawing and bulky trifluoromethyl group at the ortho position. The monomer is polymerized with terephthaloyl chloride and isophthaloyl chloride in N,N‐dimethylacetamide (DMAc) or DMAc containing LiCl using pyridine as an acid acceptor at room temperature. All synthesized polymers are somewhat crystalline and colorless. While the meta‐linked polyamide (PA2) shows excellent solubility in polar aprotic solvents, the para‐linked one (PA1) is dissolved in polar aprotic solvents containing LiCl and concentrated H2SO4. They show good thermal and thermooxidative stability as well as high melting temperatures. image