Grafting Amphiphilic Block Copolymers Onto HNTs Via RAFT Living Polymerization

RAFT living polymerization technology is a powerful tool to produce functional polymers and it has wide applicable monomers, remarkable molecular design ability and strong compatibility with other methods. Nanomaterials have shown excellent properties in optical, thermal, electrical, magnetic, mechanical and chemical aspects. Grafting functional polymer onto nanoparticle surface can not only overcome its aggregation, but also endow them with more features. In this paper, amphiphilic block copolymers were grafted onto halloysite nanotubes (HNTs) via RAFT living polymerization. The main research contents and results are as following:1. Firstly, trithiocarbonate chain transfer agent DDMAT was synthesized and applied to control homopolymerization behavior of4-vinylpyridine (4VP) and styrene (St). The results showed that DDMAT can effectively control the polymerization of4VP and St. Termination at the appropriate time (6h for4VP,19h for St) can get more active P4VP macromolecular chain transfer agent and PS macromolecular chain transfer agent. Then block copolymers were synthesized and the results showed that the macromolecular chain transfer agents P4VP and PS can effectively control polymerization of St and P4VP respectively. The obtained P4VP-b-PS and PS-b-P4VP block copolymers had narrow molecular weight distribution (PDI<1.5). The kinetics of homopolymerization and copolymerization showed that chain length of macromolecular chain transfer agents had a great influence on the polymerization rate. The polymerization rate decreased as the chain length of macromolecular chain transfer agents increased.2. In the second section, P4VP and PS polymer brushes were grafted onto the surface of HNTs via R approach. The results showed that when PS brush was grafted, additional "free" chain transfer agent was necessary to control living behavior of polymerization. In order to endow HNTs with amphiphilicity, the polymer brushes of HNTs-P4VP and HNTs-PS were extended to form P4VP-b-PS and PS-b-P4VP block copolymers, TGA, TEM and GPC were used to confirm the grafting of amphiphilic block copolymers. The results showed that well-defined amphiphilic brushes were successfully grafted onto HNTs.3. To characterize amphiphilicty of HNTs grafted with block copolymers, the dispersion behavior of modified HNTs in water/oil diphase was studied. The results showed that modified HNTs can form emulsion through self-assembly in water/oil diphase and emulsion stability depended on the hydrophilic/hydrophobic segement ratio and sequence.4. The application HNTs grafted with amphiphilic brushes was attempted. Epoxidation of soybean oil with H2O2was chosen as fundermental diphase reaction. Methyltrioxorhenium(MTO) as high efficiency catalyst was immobilized onto copolymers or brushes through coordination between MTO and P4VP segment and the obtained supported catalysts were used to catalyze epoxidation of soybean oil. When amphiphilic block copolymers acted as support, catalytic efficiency increased gradually as increased. When modified HNTs acted as support, the hydrophobic chain segment in amphiphilic brushes had a great influence on the catalytic efficiency and therefore it can adjust the hydrophobicity of polymer chain segment length in amphiphilic brushes to achieve good catalytic effect.