Synthesis Of Amphiphilic Multiblock Polymer

The synthesis and properties of block copolymers is always the attractive topic in polymer synthesis. In this thesis, the amphiphilic multiblock copolymers of styrene and 4-vinylpyridine have been prepared in the presence of 4,7-diphenyl-[1,3]dithiolane-2-thione (DPDTT) and the control on the block number of multiblock copolymer has been investigated.Homopolymerization of styrene and 4-vinylpyridine were carried out in the presence of DPDTT as RAFT agent. The polymers containing various trithiocarbonate groups per chain were prepared. The amphiphilic multiblock copolymers (P4VP-b-PS-b-P4VP)_n and (PS-b-P4VP-b-PS)_n were synthesized via copolymerization of styrene or 4-vinylpyridine by using obtained homopolymers as macro-RAFT agent. The polymerization process shows typical characteristics of living radical polymerization. Although the molecular weight distribution of whole polymer is broad, the molecular weight distribution of the block is narrow.In addition, the kinetics of styrene polymerization initiated by atom transfer radiacal polymerization (ATRP) in the presence of DPDTT and the effects of DPDTT concentration on styrene polymerization were also studied. The variation of molecular weight and the block number with the monomer conversion was studied for styrene polymerization initiated by 1-PEBr/CuBr/PMDETA in the presence of DPDTT. The ring-opening polymerization of DPDTT was controlled by atom transfer radiacal, and the block number of polymer kept constant throughout the whole polymerization process. The molecular weight of both polymer and the blocks are well controlled and close to predicted molecular weight when the concentration of DPDTT was low ([DPDTT]/[1-PEBr]=5). When the concentration of DPDTT was high ([DPDTT]/[1-PEBr]=10), the molecular weight of polymer was different from the calculated one based on ATRP, but the molecular weight of the blocks still fitted well with the theoretic values. The molecular weight distributions of polymer are around 2.0 and those of the blocks are less than 1.3.In general, the new method for synthesis of amphiphilic multiblock polymers hasbeen set up and the precisely preparation of multiblock polymers has been provided in this thesis.