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Sterically stabilized silica colloids: Radical grafting of poly(methyl methacrylate) and hydrosilylative grafting of silicones to functionalized silica
Author(s) -
Ketelson Howard A.,
Brook Michael A.,
Pelton Robert H.
Publication year - 1995
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1995.220060512
Subject(s) - materials science , polymer chemistry , methyl methacrylate , grafting , dispersity , hydrosilylation , colloid , colloidal silica , steric effects , methacrylate , polymer , polymerization , organic chemistry , catalysis , chemistry , nanotechnology , coating , composite material
Colloidal silica sols having a narrow dispersity, prepared by the ammonia‐catalyzed hydrolysis of Si(OEt) 4 , were functionalized by reaction with vinyltrimethoxysilane (H 2 CCHSi(OMe) 3 ) or methacryloxypropyltri‐methoxysilane (H 2 CCMeCO 2 (CH 2 ) 3 Si(OMe) 3 . The electrostatically stabilized colloids were stable in acetone and dimethylformamide. Radical polymerization of methyl methacrylate in the presence of either type of functionalized particle led to particles with surfacegrafted poly(methyl methacrylate) (PMMA). The efficiency of polymer grafting was shown to be related to the nature of the functional groups. The PMMA‐modified, sterically stabilized particles were colloidally stable in solvents ranging from acetone to toluene but unstable in water or hexane. The vinyl functionalized silica was alternatively reacted with HSiMe 2 ‐terminated silicones in a platinum‐catalyzed hydrosilylation. The resultant sterically stabilized particles were stable in hexane. It was thus possible to convert the unmodified silica to organo‐functionalized silica and finally to polymer‐grafted silica while maintaining colloidal stability. During the course of these modifications, the mechanism for colloidal stability changed from electrostatic to steric stabilization.