Synthesis of the Silica Particles Grafted with Poly(ionic liquid) and its Application in Polystyrene Supercritical Carbon Dioxide Foaming

Poly[2-(methacryloyloxy)ethyl]trimethylammonium tetrafluoroborate(P),as a novel poly(ionic liquid) with the strong carbon dioxide(CO2) absorption ability,was grafted onto silica particles(SiO2) by using the method of surface-initiated atom transfer radical polymerization(ATRP).The modified SiO2 was introduced into polystyrene(PS) matrix by the aid of polyacrylic acid and polystyrene diblock copolymer(PAA-b-PS) as compatibilizer,and its influences on PS foaming by supercritical CO2 were investigated.The results of Fourier transform infrared spectroscopy(FT-IR),thermo-gravimetric analysis(TGA),and transmission electron microscopy(TEM) show that P could be grafted to the surface of SiO2 by ATRP,and the resultant modified SiO2(SiO2-P) could be well-dispersed in the PS matrix.The SiO2 modified by(3-aminopropyl)triethoxysilane(KH-550)(SiO2-NH2) was also synthesised in the same manner for comparison.The cell morphology characterization obtained by using scanning electron microscopy(SEM) indicates that the morphology of PS/SiO2-NH2 composite foam has no significant difference from that of pure PS foam.However,PS/SiO2-P composite foam possesses higher cell density,smaller cell size and narrower size distribution than those of pure PS foam and PS/SiO2-NH2 composite foam.Compared with SiO2-NH2,SiO2-P exhibits a much higher heterogeneous nucleation efficiency in the foaming process.