Bio-based thermosetting resins composed of aliphatic polyol-derived polymaleimides and allyleugenol

Bio-based bismaleimide (2MPD), trismaleimide (3MGC) and tetramaleimide (4MDG) were synthesized by reactions of 4-isocyanatophenylmaleimide with 1,3-propanediol, glycerol and α,α′-diglycerol, respectively. Although 2MPD did not melt until the temperature where thermal decomposition starts, 3MGC and 4MDG exhibited broad melting temperatures with onset points at 165 °C and 124 °C, respectively. 3MGC and 4MDG were homogeneously prepolymerized at 170 °C with 2,4-diallyl-6-methoxyphenol (rAEG) which was prepared by the Claisen rearrangement of allyl-etherified eugenol (AEG). The prepolymers were compression-molded at 250 °C to produce cured rAEG/3MGC (A3Mxy) and rAEG/4MDG (A4Mxy) with the allyl/maleimide ratio of x/y = 1/1, 1/2 or 1/3. The FT-IR analysis revealed that the ene reaction of allyl and maleimide groups and subsequent addition copolymerization occurred for the cured resins. The thermal and mechanical properties of the cured resins were compared with those of the cured rAEG/4,4′-bismaleimidodiphenylmethane (BMI) (ABMxy) with the same allyl/maleimide ratio. A3M13 and A4M13 showed no inflection point of thermal expansion due to glass transition until 300 °C, which is a little lower than the thermo-degradation temperature. Flexural strengths and flexural strains at break for A3Ms and A4Ms increased with the polymaleimide contents, and those of A3M13 and A4M13 were much higher than those of ABM13.