By increasing the amount of nitrile group or adding chain extension agents or com-onomers properly

some semicompatible IPN's were obtained. Their morphology and glass transition behavior were investigated by dynamic mechanical spectroscopy and transmission electron microscopy. The phase domain sizes are about 200 A

and Tan σ values remain about 0.2-0.3 within -20℃-130℃ temperature range for PU(HTBN)/ PMMA IPN's with 24.3% acrylonitrile. Due to the strong interaction of polar groups in the PU(PCE)/PMMA IPN's

the phase domains become finer and only a single glass transition is obsered.