Studies On Preparation And Properties Of Inorganic Nano-particles/Polymer Composite

Polymer/inorganic Nanoparticle Composites (PNCs) have attracted more and more attention and given rise to their wide applications in many fields, which combine the excellent properties of inorganic compounds, organic compounds and nanometer-sized materials. In this paper, we introduced the recent research progress of PNCs. The application and achievement of polymer matrix nanometer inorganic composite were introduced firstly. The advances in the modification of inorganic nano-particles were summarized in detail. And more, the principle and technique of Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) to grow polymer from the inorganic nano-particles surface were especially reviewed. Some ideas and opinions concerning about the development of PNCs were also given.Polymer nano-microshere was one of the most important brands of the nano-materials. Polymer/inorganic nano-microshere with excellent quality has exhibited good application potential in many fields, which has become one focus in micro-cosmic material science. However, since the surfaces of inorganic particles are usually hydrophilic, while polymers are usually hydrophobic, the surfaces of inorganic particles usually need to be modified or pretreated in order to promote the compatibility between polymeric phase and inorganic phase to obtain polymer/ inorganic nano-microshere with varied kinds of morphologies. In our work, we prepared the SiO₂/polymer nano-microshere with raspberry-like morphological by a simple protocol at around ambient temperature. What's more, it will be preferable that the whole process is economical and simple without recourse to expensive, special and auxiliary comonomer or adding any surfactant. Depending on the precise formulation, the average particles size and the final silica contents of the hybrid nano-microspheres can be modulated. Both the polar monomer and the silica sol were essential for the formation of colloidally stable nanocomposite particles. The influence of other parameters was also studied. On the basis of experimental results and discussion, a possible formation mechanism of nanocomposite particles was proposed.In recent years, the modification of particles or planer surface by grafting of polymer chains has attracted much academic and industrial interest. However, conventional surface-initiated free radical polymerization, especially when confined to a thin layer, leads to a wide molecular weight distribution of the grafted polymer, largely due to termination reaction. Moreover, this approach is not suitable for preparing block copolymer. So there has been increasing research activity concerning the use Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) to grow polymer from the inorganic nanoparticles surface. In our work, a new kind of initiator, 3-(2-bromo-2-methylacryloxy)propyltriethysiliane (MPTS-Br), was prepared with a simply hydrobrominated commercial silane coupling agent (3-methacryloxy-proplytriethysilane, MPTS). It has been one-step self-assemble onto the surface of inorganic nanoparticles, and by using these initiator-modified inorganic nanoparticles as macroinitiator for SI-ATRP. Polymerization of monomer using inorganic nano-particle initiators displayed the diagnostic criteria for a controlled/"living" radical polymerization. The morphology and the dispersibility in organic solvent of the polymer-graft inorganic nanoparticles and some properties of polymer brushes were discussed in detailed.Cerium oxide (CeO₂) is an important product belonging to rare-earth family and has been widely used. In our work, Nano-CeO₂ was modified with stearic acid (SA) through one-pot boiling method to improve its dispersion and compatibility in organic phase and would provide chance for CeO₂ to be used in polymer field industrially. And then, polystyrene/cerium oxide (PS/CeO₂) nanocomposite was accomplished by in-situ emulsion polymerization in presence of modified nano-cerium oxide. GPC, FT-IR and XPS proved that nano-cerium oxide should play an important role in improving ultraviolet stability of polymer matrix. Nano-cerium oxide could adsorb ultraviolet and transmit light energy into thermal energy or sub-irradiation either of which is less harmful to polymer matrix and the effect of preventing polymer from degrading was achieved. According to DSC and TG analysis, thermal stability of PS/CeO₂ nanocomposite was increased dramatically compared with that of pure PS. When the modified CeO₂ content was below 1 wt%, it could be uniformly dispersed in PS on nanometer order as observed by SEM, and maybe strengthen and toughen material simultaneity.Some important results of my work as follows: (1) We prepared a new kind of SiO₂/polymer nano-microshere with raspberry-like morphology using cheap, commercially amorphous aqueous silica sol at ambient temperature. (2) We studied a simple method to immobilize theα-bromoester initiator on the surface of inorganic nanoparticles, which could serve as ATRP initiator. Since surface-tetheredα-bromoester initiator only underwent one-step heterogeneous process, the initiator density on the silica nanoparticles was high. Therefore, structurally well-defined, densely grafted and thick-coated polymer layer by ATRP could be obtained. (3) Polystyrene/cerium oxide (PS/CeO₂) nanocomposite was accomplished by simple one-pot boiling method and in-situ emulsion polymerization. The robustness and simplicity of this method may make large-scale manufacture of this nanocomposite possible.