The Preparation And Formation Mechanism Of Guava-like Poly（MMA-co-St）/SiO₂ Nanocomposite Particles Via In-situ Polymerization

Baking film formation of waterborne complex latex in the presence of inorganic particles is a common formation process in the high-temperature coating production fields of textiles, papermaking, leather, and construction. However, the migrating and clustering behavior of unrestricted inorganic functional particles often lead to forming the latex film with uncontrollable microphase structure and worse quality during conventional baking film formation process of waterborne complex latex. However, Guava-like polymer/SiO2 nanocomposite particles were prepared through in situ polymerization may have the ability to restrict the motion of inorganic functional particles in latex during film formation, and then formed a controllable microphase structure latex film. Therefore, in order to accurate study the influence rule of composite latex structure relative to the microphase structure and performance of film, a series of polymer/SiO2 grafting composite latex particles with different graft status (grafting density, grafted chain flexibility and crosslinking degree of grafted chain) need to be elaborately prepared via in situ polymerization.In this study, nanosilica particles(SiO2), methyl methacrylate(MMA) and styrene(St) have been used as the typical functional nanoparticles and monomers, respectively. The SiO2 in ethanol were modified with typical silane coupling agent 3-(trimethoxysilyl) propyl methacrylate(MPS) and octyltrimethoxysilane(OTMS) respectively, and then the solvent replacement technique was used to prepare aqueous or monomer dispersion of SiO2 nanoparticles. A series of guava-like polymer/SiO2 nanocomposite particles were prepared through in situ (mini)emulsion polymerization. Finally the formation mechanism of guava-like polymer/SiO2 NCPs in the systems of in situ (mini)emulsion polymerization were uncovered.First of all, the monomer dispersion of SiO2 modified with MPS or OTMS were prepared, then guava-like polymer/SiO2 nanocomposite particles were prepared via in situ miniemulsion copolymerization of MMA and St using high coupling density (MPS or OTMS)-modified SiO2. Formation mechanism of guava-like polymer/SiO2 nanocomposite particles in miniemulsion system is droplet nucleation by analyzing the polymerization kinetics and the change of the dispersed phase size in the polymerization process.Subsequently, guava-like polymer/SiO2 nanocomposite particles were prepared via in situ emulsion copolymerization of MMA and St using different coupling density (MPS or OTMS)-modified SiO2-And it was discovered that reactive group species of SiO2 surface, coupling density of SiO2 surface, monomer ratio and the content of SiO2 can influence the morphology of nanocomposite particles. The guava-like nanosilica cluster is a thermodynamics steady-state structures comparing with the baking film formation of mixing of inorganic functional particles and latex.Finally, the formation mechanism of guava-like polymer/SiO2 nanocomposite particles in the systems of in situ emulsion polymerization was proposed and compared with the formation mechanism in situ miniemulsion polymerization system. The morphological evolution of the polymer/SiO2 nanocomposite particles, and the role of the grafting reaction and nucleation pattern in the formation of the guava-like polymer/SiO2 nanocomposite particles were systematically investigated. A formation mechanism of guava-like polymer/SiO2 nanocomposite particles based on the enhanced homogenous nucleation through the grafting reaction to SiO2 was proposed. And the emulsion polymerization is proved to be the better system to prepare a typical guava-like polymer/SiO2 nanocomposite particles.The research mainly focus on the preparation of controllable composite microspheres morphology and its studying of formation mechanism. The results can provide raw materials for subsequently study of microphase structure formation and regulation of baking film in the presence of polymer/SiO2 complex latex, and have the guidance meaning for preparation of other special performance guava-like polymer/inorganic nanocomposite particles.