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

• Published in: Macromolecular chemistry and physics Vol. 216; no. 12; pp. 1341 - 1347
• Main Authors: Kim, Sun Dal, Byun, Taejoon, Lee, Byungyong, Kim, Sang Youl, Chung, Im Sik
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.06.2015; Wiley Subscription Services, Inc
• Subjects: aromatic polyamides; Chlorides; Diamines; high performance polymers; Jewelry; Melting; Monomers; Polyamide resins; Solubility; Solvents; trifluoromethyl groups
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.201500013

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. A series of rigid‐rod polyamides with trifluoromethyl pendant groups are prepared via polycondensation of the diamine monomer and diacid chlorides. Synthesized polyamides are colorless and possess good thermal stabilities owing to the incorporation of trifluoromethyl pendant groups. The meta‐linked polyamide shows good solubility in organic solvent whereas the para‐linked one exhibits limited solubility.