Cross-linking of Grafted Copolymer on Colloidal Silica and Introduction of Surface Amino Group

To obtain polymer-modified silica (550 nm diameter), trimethoxysilyl-terminated poly(glycidyl methacrylate-co-methyl methacrylate) with epoxy ring (to prevent the formation of carboxyl group) was successfully synthesized. Then, the cross-linking of the grafted copolymer on silica was made using ethylenediamine or hexamethylenediamine of varying alkyl chain lengths, and the stability of cross-linked silica particles was investigated in alkaline aqueous solution. Cross-linked polymer-modified silica based on diamines exhibited much lower reduction rate (in wt %) of the attached polymer to silica than uncross-linked polymer-modified silica. In particular, cross-linked silica composites by ethylenediamine had more stability than cross-linked silica composites by hexamethylenediamine. Finally, the cross-linking reaction of grafted-polymer on silica particles by diamines was confirmed by the 13C CP/MAS NMR spectra measured on polymer-modified silica composites.