Living Polymerization For Homopolymer And Copolymer Of Polyacrylonitrile

Two kinds of chain transfer agents, S, S’-Bis (a, a’-dimethyl-a"-acetic acid)-trithiocarbonate (TRIT) and Di (thiobenzoyl) Disulfide (DTBD) were synthesized firstly. Then polyacrylonitriles (PAN) with narrow molecular weight distribution (PDI) using TRIT and DTBD as chain transfer agents were prepared, and the PDI were1.10and1.19, respectively. While TRIT as chain transfer agent, the monomer conversion reached more than80%, which indicated that two chain transfer agents controlled the polymerization of acrylonitrile well, and that TRIT was a very efficient chain transfer agent. Carboxyl-terminated polyacrylonitrile and polystyrene as macro-RAFT agents were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using TRIT as the chain transfer agent. Poly (acrylonitrile)-b-poly (styrene)-b-poly (acrylonitrile)(PAN-b-PS-b-PAN) and poly (styrene)-b-poly (acrylonitrile)-b-poly (styrene)(PS-b-PAN-b-PS) triblock copolymers were synthesized by using acrylonitrile and styrene as monomers and macro-RAFT agents as the chain transfer agents, respectively. It is noteworthy that the block copolymer synthesized with this method containing carboxyl functional groups, had many potential applications. Atomic force microscope (AFM) thermogravimetric analysis (TGA), thermomechanical analysis (TMA) and Raman spectra were used to study the microphase separation structure and pyrolysis behavior of the block copolymer films. Results showed that after stabilization at250℃and pyrolysis at600℃, thin films of PS-b-PAN-b-PS block copolymer carbonized to uniform graphite structure with size of about75nm.In addition, high molecular weight polyacrylonitrile and polyacrylonitrile-methyl methacrylate random copolymer were synthesized in DMF using lithium1,2-bis (diethylamino)-2-oxoethanolate as initiator in the range-60to-10℃.1H-NMR, FT-IR and gel permeation chromatography (GPC) were used to characterize the molecular structures and molecular weights of the resulting products.13C-NMR and FT-IR were used to study effects of different reaction conditions on side reactions and tacticity of polymerization products. The results show that, polyacrylonitrile prepared by this method had less cyclization structures, and tacticity increased10percents than normal radical polymerization.