Synthesis and Characterization of Flexible Meta‐Aramid Modified with 4,4′‐Methylenedianiline.

Meta‐aramids (poly(m‐phenylene isophthalamide), PMIA) have excellent flame, heat resistance, and electrical insulation. However, the rigid molecular backbone of PMIA and the strong hydrogen bonding force between its molecular chains make it poorly flexible, soluble, and processed. In this study, a series of modified PMIA containing methylene groups on the main chain (APMIA‐n, where n is the molar fraction of 4,4′‐methylenedianiline (MDA) in m‐phenylenediamine, and n = 0, 5, 10, 15, 20) is synthesized by introducing different ratios of MDA into PMIA by copolymerization. APMIA‐n films are prepared by the solution casting method. The results show some improvement in the solubility of APMIA‐n in polar organic solvents such as N,N‐dimethylformamide and dimethyl sulfoxide. With the increase of the molar fraction of MDA, the tensile modulus of obtained APMIA‐n films decrease from 4.62 to 2.98 GPa, indicating that the flexibility of the films is evidently increased. APMIA‐n films are self‐extinguishing which suggests that the addition of MDA during copolymerization has a slight influence on the flame resistance of the synthesized PMIA. Moreover, APMIA‐n films containing MDA components exhibit good optical transparency, which may expand the application of PMIA in more fields such as packaging and screen display. [ABSTRACT FROM AUTHOR]