Stnthesis Of Branched Polymers By Controlled Radical Polymerization

1. Comb-like polymers with poly(N-phenyl maleimide-alt-styrene) main chain and polystyrene side chains have been synthesized by combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP). In the first step, poly(N-phenyl maleimide-alt-p-chloromethyl styrene) with controlled molecular weight and narrow molecular weight distribution was prepared by RAFT copolymerization of N-phenyl maleimide and p-chloromethyl styrene with AIBN as an initiator and 2-(ethoxycarbonyl) prop-2-yl dithiobenzoate as a chain transfer agent. This alternating copolymer had one active benzyl chlorine atom per repeating monomer unit, which can initiate ATRP of styrene. In the second step, the obtained poIy(N-phenyl maleimide-alt-p-chloromethyl styrene) was used as the macroinitiator for ATRP of styrene in the presence of CuCl/2,2'-bipyridine catalyzing system, generating comb-like polystyrenes with controlled structures.2. An asymmetric difunctional initiator 4-(2-bromo-2-methyl propionyloxy)-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-Br) was synthesized by reacting 4-hydroxyl-2,2,6,6-tetramethyl-l-piperidinyloxy with 2-bromo-2-methyl propionyl bromide. Stable free radical polymerization (SFRP) of styrene was then carried out using dibenzoyl peroxide as initiator in the presence of TEMPO-Br. The obtained polystyrene had an active bromine atom for atom transfer radical polymerization (ATRP) at the a-end of the chain and was used as the macroinitiator for ATRP of methyl acrylate, ethyl acrylate and styrene to prepare diblock copolymers. The molecular weights of the resulting block copolymers at different monomerconversions shifted to higher molecular weights without any trace of the macroinitiator, and increased linearly with monomer conversion.3. 4-(2,2-bis-(methyl cc-bromo isobutyrate)-propionyloxy)-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-(Br)2) was synthesized by reacting 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy with 2,2-bis- (methyl a-bromo isobutyrate) propanic acid. SFRP of styrene was carried in the presence of TEMPO-(Br)2. The obtained polystyrene was used as the macroinitiator for ATRP of methyl acrylate, ethyl acrylate and styrene to prepare milktoarm star copolymers. The molecular weights of the resulting copolymers at different monomer conversions shifted to higher molecular weights without any trace of the macroinitiator, and increased linearly with monomer conversion.4. A novel inimer was synthesized by the reaction of 4,4'-azobis(4-cyanovaleric acid) with 2-hydroethyl methacrylate in the presence of 4-(dimethylamino)pridine 4-methylbenzenesulfonate and dicyclohexylcarbodiimide. With the inimer as an initiator, SFRP of styrene mediated by 4-hydroxyl-2,2,6,6-tetramethyl-l-piperidinyloxy was carried out. GPC traces of polystyrenes emerged multimodel with the monomer conversion increased, showing the branch structure of the obtained polystyrene. In addition, the branch structure was also verified by ' H NMR and hydrolysized product of polystyrene.5. a-Bromoacrylate was used as a functionl monomer for preparation of graft copolymers via ATRP. In the first part, poly(ethyl acrylate)-g-poly(methyl methacrylate) was synthesized via atom transfer radical polymerization with poly(ethyl acrylate-co-ethyl 2-bromoacrylate) as the macroinitiator, which was obtained by emulsion copolymerization of ethyl acrylate and ethyl 2-bromoacrylate. The molecular weights of the graft copolymers increased linearly with the conversion of methyl methacrylate, showing that the grafting copolymerization was a living process. In the second part, comb-like poly(methyl methacrylate) was synthesized by atom transfer radical polymerization of methyl methacrylate with poly(ethyl 2-bromoacrylate) as a macroinitiator, which was prepared by conventional free radical polymerization of ethyl 2-bromoacrylate. In the third part, ethyl cc-bromoacrylate-PCL...