Synthesis and characterization of new soluble polyaspartimides derived from bis(3-ethyl-5-methyl-4-maleimidophenyl)methane and various diamines

A series of new linear polyaspartimides was obtained via a Michael addition reaction from bis(3-ethyl-5-methyl-4-maleimidophenyl)methane (BEMM) with various aromatic diamines in m-cresol in a 1:1 molar ratio. The molecular weight and yield of these polymers tend to increase with increasing monomer concentration. It was observed that a maximum molecular weight was reached at around 0.72 mol l−1 of monomer concentration. Both the yield and the molecular weight of the polymers increased with reaction times up to around 100 h. The inherent viscosities of the polymers varied from 0.42 to 0.70 dl g−1. The polymers had number-average molecular weight and weight-average molecular weight in the range of 9400–20 000 and 24 000–68 000, respectively. All polymers are amorphous and soluble in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, DMF, dimethyl sulfoxide, pyridine, m-cresol, cyclohexanone and tetrahydrofuran. The polymers had high glass transition temperatures in the range of 242–308°C and good thermal stability — 10% weight loss temperatures in the range of 408–459°C in air and 396–421°C in nitrogen.