A novel poly(methyl methacrylate-co-vinyl acetate) / poly(ethylene-co-vinyl acetate) (poly(MMA-co-VAc)/EVA) alloy with temperature dependent optical properties was prepared by radical copolymerization induced spinodal decomposition(SD) in the mixture of MMA/VAc/EVA. The structural development during copolymerization was investigated by time resolved light scattering(TRLS) and scanning electron microscopy (SEM). As the copolymerization of MMA and VAc proceeded

phase separation took place via SD. This was supported by the characteristic change in light- scattering profiles with recation time. SEM photographs show that the phase separated structure is isolated poly(MMA-co-VAc) rich domains dispersed in EVA rich matrix.The optothermal properties of poly(MMA-co-VAc)/EVA alloy were abserved by transmittivity measurement

which the increase of temperature and vice varsa.Hence

poly(MMA-co-VAc)/EVA alloy is of potential use in applications such as temperature-controlled optical devices.