Study On The Preparation Of Polymer/Silica Hybrid Materials

In this paper, silica-based macromonomer and macroinitiator were synthesized through the silica surface modifications. Polymer/silica hybrid materials were prepared by conventional radical copolymerization of silica-based macromonomer with styrene and methyl methacrylate, respectively. In addition, silica surface-grafted polymers were prepared using atom transfer radical polymerization (ATRP) initiated by silica-based macroinitiator. The main contents were as follows: Two-stage process has been developed to synthesize the macromonomer through surface-modification of silica with polymerizable vinyl groups. Firstly, the silica surface was treated with excess toluene-2,4-diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). The main effecting factors on the reaction of silica with TDI were studied by determining the reaction extent of hydroxyl groups at the surface of silica particles. FTIR spectroscopy was employed to characterize the macromonomer. TEM images showed that the silica particles remained unaggregated after surface modification. The macromonomer have been used to copolymerize with vinyl monomers, i.e., styrene or methylmethacrylate, to prepare hybrid materials. The main effecting factors, such as ratios of vinyl monomer to the macromonomer together with the polymerization time, were studied by determining the extent of copolymerized vinyl monomer. The FTIR, TGA and DSC spectra were employed to characterize the hybrid materials. DSC results revealed that the glass transition temperatures (Tgs) of the hybrid materials were higher than that of the corresponding homopolymers. The distribution of silica particles in the hybrid materials was investigated by SEM, which showed that the silica particles were uniformly dispersed in the polystyrene matrix. Immobilization of the ATRP initiator on the silica surface was achieved in three consecutive steps. Poly(glycerol methyacrylate) and polystyrene chains were grafted from silica nanoparticles surface by ATRP, which was initiated by the as-synthesized silica-based macroinitiator. TEM was used to observe the morphology of the poly(glycerol methyacrylate)/silica hybrid particles. FTIR, 1H NMR and GPC were employed to characterize the surface grafted-polystyrene.