The Preparation Of Polymer/Silica Nanocomposite Latex And Properties Of The Film

In recent years,the strategy to fabricate polymer/silica nanocomposites is of burgeoning interest,not only because such materials have the strength of organic and inorganic materials,but also because such materials can display novel and enhanced properties(e.g.mechanical,chemical,electrical,thermal and optical).In this study,polymer/silica nanocomposite spheres with raspberry-like were obtained via surfactant-free methods,and properties of the films were investigated. Also Poly(St-BA-AA)/SiO₂ nanocomposite emulsions were prepared via in suit or blending method.Some ordered porous structures were observed after the latex was coated on the substrate and dried at a high temperature;or some ordered colloid crystals were obtained at room temperature.Temperature,monomer composites, nanosilica content,particle size and etc were studied on the influence of the morphology of the ordered structure.And the properties of the films were investigated by TEM,SEM,XPS and Reflection spectra,etc.All the research contents and results are as follows:(1) We used Poly(vinyl acetate)(PVAc) as the monomer and successfully synthesized a series of long-stand stable raspberrylike PVAc/SiO₂ nanocomposite particles via a "surfactant-free" heterophase polymerization in the presence of an ultrafine aqueous silica sol and water as the continuous phase.Since the surface of silica particle is surrounded by hydroxyl group,the hydrogen-bond between PVAc and silica should promote the compatibility between polymeric phase and nanosilica phase.Some influencing parameters such as initial silica varieties,silica content were investigated in detail,and a possible formation mechanism of raspberrylike nanocomposite particles was also discussed.And properties of the films such as water resistance and hardness were investigated.(2)This part presents a novel and facile method for the fabrication of nanocomposite films with ordered porous structures.In this approach,a water-borne poly(styrene-co-butyl acrylate-co-acrylic acid) / silica nanocomposite emulsion was synthesized in situ emulsion polymerization.When this latex was dried to form a film at a high temperature(above 100℃),an ordered porous structure could be directly obtained in the nanocomposite film.This was probably during a fast evaporation rate of water,silica particles transform into hard silica framework via the condensation of silianol groups.Meanwhile,soft polymer particles can easily collapseand immigrate into the voids existing in silica framework to form ordered porous structure in the nanocomposite film.SEM,TEM were employed to observe the morphology,XPS and particle analyzer were used to analyze the surface composition of the ordered porous nanocomposite film and the particle size,respectively.(3) An one-step strategy to fabricate large-scale ordered colloid crystals has been proposed,in which a nanocomposite emulsion composed of polymer latex and colloidal silica is blended first,and then drying on a substrate under room temperatures to directly obtain a robust film with three-dimensionally array of colloid spheres.This strategy is really simple and inexpensive:Neither complex processes nor special equipments are needed,as large as several square meters colloid crystal can be fabricated on any substrates without any templates.This technique presents a new paradigm in the preparations of colloid crystals.The particle size of polymer particles,morphology and optical properties of colloid crystal films were investigated by TEM,SEM,Reflection spectra and particle analyzer.The films have very beautiful iridescence phenomena and regular periodicity.