Preparation Of Ormosil Via Ultrasonic Irradiation And In-situ Miniemulsion Polymerization For Nanocomposites

The monomer droplet with the size of50-500nm can be used as nanoreactor, due tothe feature that droplet nucleation is the main nucleation in miniemulsionpolymerization, thus, miniemulsion polymerization is suitable for preparation oforganic-inorganic nanocomposites. The bad compatibility between inorganic particlesand organic monomers leads to the agglomeration of inorganic nanoparticles whendispersed in organic matrix, which decreases the properties of the composites. Itposses theoretical and practical importance to study the surface modification ofinorganic nanoparticles.In present study, due to the multieffects of ultrasound such as activation ofinorganic nanoparticles、 dispersion、 initiation of polymerization, encapsulatingpolymerization of monomers on the surface of silica was applied to modify silica.And the tests by nanosizer、 Thermogravity(TG)、 Fourier-transffer InfraredSpectroscopy(FTIR) and Transmission electon microscopy(TEM) et al showed thatorganic encapsulated silica was successfully prepared. The modified silica could bewell dispersed in monomers, by miniemulsion polymerization, Polyacrylates/silicananocomposite latex was prepared. The TEM test showed that multicore-shellnanocomposite particle was prepared and the Scanning electron microscopy(SEM)image of frature surface of latex film demonstrated that the modified silica could bewell dispersed in matrix without any aggregation. The tensile tests of latex filmsshowed that the tensile strength increased with the increase of silica content, usingpolymer with high Tg to modify silica nanopariticles, these particles could enhancethe tensile strength of nanocomposites, while using polymer with lower Tg to modifysilica nanoparticles, the modified silica could improve the toughness ofnanocomposites.Based on the above study, with the assistance of ultrasonic, Octamethylcyclo-tetrasiloxane(D4) and a little of silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) were sufficiently mixed with silica sol and thein-situ ring-opening polymerization of D4and co-condensation with KH560on thesurface of silica nanoparticles, catalyzed by dodecylbenzene sulfonic acid (DBSA),were enhanced as well. The polydimethylsiloxane (PDMS) modified silica was obtained. The PDMS-modified silica sol was dispersed in the mixed monomers ofmethylmethacrylate(MMA) and butylmethacrylate(BA). Then miniemulsionpolymerizations of the acrylate monomers containing PDMS-modified silica sol werecarried out, with PDMS as hydrophobe to inhibit the Ostwald ripening of themonomer droplets and neutralized DBSA as emulsifier, both preexisted in the PDMS-modified silica sol. The composite latex was obtained via miniemulsionpolymerization. FTIR, TGA, TEM, Malvern Nanosizer and water contact angle testswere utilized to characterize the modified silica and the composite latex. The resultsshow that silica is grafted and encapsulated by PDMS and KH560with chemicalbonds and is well dispersed in monomers, and the generated PDMS improves thehydrophobicity of the film of nanocomposite latex. The average size ofnanocomposite particles with a (multi)core-shell structures is98nm when the silicamass ratio is3%of the monomers.