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6612973 
Journal Article 
Silica/polymer core-shell particles prepared via soap-free emulsion polymerization 
Ishihara, M; Kaeda, T; Sasaki, T; , 
2020 
Yes 
E-polymers
ISSN: 1618-7229 
WALTER DE GRUYTER GMBH 
BERLIN 
20 
1 
254-261 
English 
WOS:000540478400001 
In this study, core-shell particles were prepared as a hybrid material, in which a thin polymer shell was formed on the surface of the SiO2 sphere particles. The core-shell structure was successfully achieved without adding a surfactant via simple free-radical polymerization (soap-free emulsion polymerization) for various monomers of styrene, methyl methacrylate (MMA), and their derivatives. MMA formed thin homogeneous shells of polymer (PMMA) less than 100 nm in thickness with complete surface coverage and a very smooth shell surface. The obtained shell morphology strongly depended on the monomers, which suggests different shell formation mechanisms with respect to the monomers. It was found that the cross-linking monomer 1,4-divinylbenzene tends to promote shell formation, and the cross-linking reaction may stabilize the core-shell structure throughout radical polymerization. It should also be noted that the present method produced a considerable amount of pure polymer besides the core-shell particles. The glass transition temperatures of the obtained polymer shells were higher than those of the corresponding bulk materials. This result suggests strong interactions at the core-shell interface. 
core-shell particles; cross-link; glass transition; silica; soap-free polymerization