A series of 3-(trimethoxysilyl)propyl methacrylate(MPS) modified silica/poly(methyl methacrylate) composites(SiO2/PMMA) with different silica content and PMMA grafting percentage were prepared via in situ bulk polymerization.The grafting and crosslinking status of the composites were analyzed by Soxhlet extraction

and three parts were found:PMMA solution with free silica in extract solvent

PMMA film with connected silica on the inner wall of filter bag

PMMA gel with crosslinked silica in the inner of filter bag.The distribution of PMMA and silica in the above three parts were obviously affected by the silica content and PMMA grafting percentage.Based on the etching of silica by HF

the PMMA grafting percentage

the molecular weight of grafted PMMA and the grafting density of PMMA chain on different silica particles were measured by gravimetric method and gel permeation chromatography (GPC).The grafting percentage

molecular weight and grafting density of PMMA in gel were more than those in film

and the grafting density of PMMA chain both in gel and in film were close with the one of MPS in silica/MMA dispersion.The above phenomena can be attributed to the grafting of PMMA from the anchored MPS on silica surface and the chemical bonding between the PMMA chains grafted on different silica.Especially

in the case of higher silica content and higher MPS coupling amount

a three-dimensional crosslinked structure with silica as crosslinking point can be easily formed in the part and even in the whole of the SiO2/PMMA composite.The regulation to the grafting and crosslinking structure was of benefit to improving the composites properties

especially to the dispersibility of the accumulated silica on the melting shear field.