Synthesis and characterization of (4-arm-star-PMMA)/PMMA-g-SiO2 hybrid nanocomposites

Abstract

This study provides a route to prepare 4-arm star poly(methyl methacrylate) (4sPMMA)/PMMA grafted SiO2 (PMMA-g-SiO2) hybrid nanocomposites that can be used as 3D printing material and filler for dental materials. First, 4sPMMA was synthesized via atom transfer radical polymerization with low metal catalyst concentration. Modified colloidal silica nanoparticles (MCSPs) were synthesized by grafting 3-methoxypropyl trimethoxysilane (MPS) onto the surface of colloidal silica nanoparticles (CSPs) and then dispersed in the solution of methyl methacrylate monomer in dioxane. The mixture of 4sPMMA and MCSPs solutions was degassed and replaced in an oil bath at 70-75°C; the reaction was continued with α,α′-azobis(isobutyronitrile) as an initiator for 24 h to form 4sPMMA/PMMA-g-SiO2 hybrid nanocomposites. Viscosity measurement showed that viscosity of the hybrid was increased with increasing MPS loading used in modification of CSPs, which verified that PMMA had been grafted onto MCSPs. Fourier transform infrared spectra of the hybrid nanocomposites demonstrated the strong molecular interaction between MCSPs and polymer matrix, and 1H NMR spectra confirmed the formation of PMMA-g-SiO2. Field emission scanning electron microscopy and transmission electron microscopy images revealed that MCSPs were well dispersed in polymer matrix with the size of about 20-30 nm. Thermal stability of the hybrid nanocomposites was improved compared with PMMA made from free radical polymerization.