Synthesis and characterization of novel polyaspartimides derived from 2,2?-dimethyl-4,4?-bis(4-maleimidophenoxy)biphenyl and various diamines

A novel bismaleimide, 2,2′-dimethyl-4,4′-bis(4-maleimidophenoxy)biphenyl, containing noncoplanar 2,2′-dimethylbiphenylene and flexible ether units in the polymer backbone was synthesized from 2,2′-dimethyl-4,4′-bis(4-aminophenoxy)biphenyl with maleic anhydride. The bismaleimide was reacted with 11 diamines using m-cresol as a solvent and glacial acetic acid as a catalyst to produce novel polyaspartimides. Polymers were identified by elemental analysis and infrared spectroscopy, and characterized by solubility test, X-ray diffraction, and thermal analysis (differential scanning calorimetry and thermogravimetric analysis). The inherent viscosities of the polymers varied from 0.22 to 0.48 dL g−1 in concentration of 1.0 g dL−1 of N,N-dimethylformamide. All polymers are soluble in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, pyridine, m-cresol, and tetrahydrofuran. The polymers, except PASI-4, had moderate glass transition temperature in the range of 188°–226°C and good thermo-oxidative stability, losing 10% mass in the range of 375°–426°C in air and 357°–415°C in nitrogen.