Preparation of PDMS-ormosil and its application in miniemulsion polymerization

With the assistance of ultrasound, octamethylcyclotetrasiloxane (D4) and slight silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) were sufficiently mixed with silica sol, and the in situ ring-opening polymerization of D4 on the surface of silica nanoparticles, catalyzed by dodecylbenzene sulfonic acid (DBSA), was enhanced as well. Thus, polydimethylsiloxane (PDMS)-modified silica (PDMS-ormosil) mixture was obtained. A slight addition of silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) could significantly enhance the modified efficiency. The PDMS-ormosil mixtures were directly dispersed in the mixed monomer methyl methacrylate and butyl methacrylate. Then, miniemulsion polymerizations of acrylate monomers containing PDMS-ormosils were carried out, with free PDMS as hydrophobe and neutralized DBSA as emulsifier, both preexisted in the PDMS-ormosil mixture. Thus, the troubles of separation, purification, and redispersion in the traditional techniques can be omitted. Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscope, scanning electron microscope, and water contact angle tests were utilized to demonstrate that nanocomposite particles with a core–shell structure were synthesized; when the silica content was 3 wt% of the monomers, the average particle size was 97 nm, and the generated PDMS improved the hydrophobicity of the nanocomposite latex.