Two maleimido end-capped poly(ethylene glycol) (m-PEG) of different molecular weights were synthesized and blended at various proportions with bismaleimide resin (4,4Ј-bismaleimido diphenylmethane) (BDM). The curing behavior and the thermal properties of the m-PEG/BDM blends were studied and presented here. It was found that the addition of m-PEG enhanced the processability of the BDM resin significantly. The processing window of the BDM resin was increased from approximately 20 to 80°C. The addition of m-PEG modified resins, however, resulted not only in the reduction in the thermal stability of the blended BDM resin but also elevation of the coefficients of thermal expansion. The changes in thermal/mechanical properties of the blends were found to be proportional to the amounts of m-PEG incorporated. It was observed that the curing behavior, and thermal and mechanical properties, of the blends were independent of the molecular weight of the PEG segment.

Two maleimido-end-capped poly(ethylene glycol) (m-PEG)-modified bismaleimide (BMI) resins [4,4Ј-bismaleimido diphenylmethane (BDM)] were synthesized from poly(ethylene glycol) (PEG) of two different molecular weights. A series of m-PEGs and unmodified BDM were blended and thermally cured. The effect of incorporating m-PEG side chains on the morphology and mechanical behaviors of BMI polymer were evaluated. The mechanical properties of these m-PEG-modified BMIs that were evaluated included flexural modulus, flexural strength, strain at break, fracture toughness, and fracture energy. The morphology of these blends was studied with scanning electron microscopy. All the m-PEG-modified BMI polymers showed various degrees of phase separation depending on the molecular weights and concentrations of the m-PEG used. The effects of these morphological changes in the m-PEG-modified BMI polymers were reflected by the improved fracture toughness and strain at break. However, there was a reduction in the flexural moduli in all m-PEG-modified BMI polymers.