Nanosilica particles well dispersed in ethanol were modified by 3-(trimethoxysilyl)propyl methacrylate (MPS) and then re-dispersed into methyl methacrylate (MMA) and poly(methyl methacrylate) matrix via a media replacement process and an in situ bulk polymerization process

respectively.The MPS modified status of silica particles and its effects on the dispersion of silica particles in different media and polymer matrix were systematically investigated by FTIR

TG

DLS and TEM.It was found MPS oligomer was the main form for MPS coupling on silica particles surface.Excessive MPS dosage not only resulted in the formation of MPS homo-polymeric particles in media phase

but also the MPS oligomer thick layer on silica surface

which would inevitably induce the small-scale aggregation of silica particles.There existed an appropriate MPS coupling amount for excellent silica dispersity

which is mainly related with the apparent coupling density of MPS molecules on silica particles surface.When the apparent coupling density is 1.3~5.6 mol(m2SiO2)-1

the MPS coupling efficiency is acceptable and the modification of silica particles is sufficient.Only on this state

silica particles can be dispersed in the monomer and polymer matrix at the primary particles size level

even in the case of 20% silica content.The silica/monomer dispersion prepared via the above processes exhibited high silica dispersity

high silica content

high storage stability and high grafting controllability on silica surface.All of them imply that this kind of dispersion is avail to prepare silica/PMMA composite microspheres via in situ heterogeneous polymerization

and these microspheres would possess controllable morphology and controllable graft interface.