Synthesis and characterization of thermo-responsive PNIPAm-grafted silica microparticles using MOP-modified mesoporous silica micro-spheres prepared by emulsion-gel method

Abstract

The composites of poly(N-isopropylacrylamide) (PNIPAm) and mesoporous silica micro-spheres were synthesized using 3-(trimethoxysilyl) Pr methacrylate (MOP) as a silane coupling agent. First, MOP-modified silica particles were prepd. by the sequential addn. of tetra-Et orthosilicate (TEOS) and MOP into W/O emulsion consisting of aq. soln. of SDS or Tween 20 and n-octanol of hydroxypropyl cellulose (HPC) and Span 80. The effect of MOP on the formation of the silica particles was investigated by the variation of the reaction time of TEOS before the addn. of MOP. Second, PNIPAm-grafted mesoporous silica micro-spheres were synthesized by radical copolymn. of MOP-modified silica particles and NIPAm monomers. N,N`-methylene bisacrylamide (MBA) and N,N,N`,N`-tetramethylethylenediamine (TEMED) were used as the crosslinking agent and the accelerator. The formations of MOP-silica and PNIPAm-silica composites were characterized by IR, BET, SEM and TGA. The phase transition of synthesized thermo-responsive polymers was characterized by DSC.