Dithiocarbamate telechelic polymers: Synthesis and block copolymerization

The iniferter method of Otsu was studied for the synthesis of polyvinyl block copolymers of relatively low molecular weight using tetramethylthiuram disulfide (TD) and benzyl N,N-diethyldithiocarbamate (BDC) as initiator. Considering the low quantum yield of dissociation (?_d) of TD (2,5 · 10^?3 in cyclohexane), TD was used as thermal initiator (95°C) for the synthesis of dithiocarbamate-polystyrene (TD-PS) telechelics. ¹³C NMR analysis of this TD-PS shows two ¹³C?S signals corresponding to two different end-groups: Et₂N? CS? S? CH(C₆H₅)? CH₂? and Et₂N? CS? S? CH₂? CH(C₆H₅)? . Several styrene polymerizations were also carried out in presence of azoisobutyronitrile (AIBN) as thermal initiator and TD as chain-transfer reagent. Depending on the mole ratio AIBN/TD, mono- and difunctional TD-PS's are formed, as evidenced by NMR analysis. These TD-PS's were used for the photochemical initiations of ethyl acrylate (EA), acrylic acid (AA) and methyl methacrylate (MMA). It is assumed that the quantum yield of dissociation of the dithiocarbamate end-group is equal to that of BDC (?_d : 0,06). TD-PS nonfunctional polymers were also prepared, either photochemically by dissociation of BDC, or thermally in presence of AIBN and BDC as transfer agent. They were used for block copolymerization with MMA. Inversely, TD-PMMA's were prepared in a first step; in this case ?_d = 0,026. They were then used for the polymerization of EA. The block copolymers were fractionated; their composition and molecular weights were determined by ¹H NMR and gelpermeation chromatography, respectively.