Synthesis Of Functional Polymer Via Reversible Addition-Fragmentation Chain Transfer (RAFT)Polymerization

A series of functional polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, undergoing a living free-radical polymerization mechanism.2-Hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) were copolymerized in1,4-dioxane with2,2’-azobisisobutyronitrile as initiator and2-(ethoxycarbonyl)prop-2-yl dithiobenzoate as RAFT agent. The molecul-ar weight of poly(HEMA-co-MMA) obtained was well-controlled and the polydispersity was low. The hydroxyl group from HEMA underwent addition reaction with1,4-cyclohexanedimethanol divinyl ether in the presence of pyridinium p-toluenesulfonate, generating a copolymer network with acetal component in the crosslinking segment. The crosslinking time depended on the molar ratio of HEMA and MMA in the poly(HEMA-co-MMA). Treated in strong acid, the polymer network exhibited degradable capability due to the acetal structure, but the backbone chains of poly(HEMA-co-MMA) remained without decomposing.Acrylic acid (AA) and methyl methacrylate (MMA) were copolymerized in1,4-dioxane with2,2’-azobisisobutyronitrile as initiator and2-(ethoxycarbo-nyl)prop-2-yl dithiobenzoate as RAFT agent. The molecular weight of poly(AA-co-MMA) was well-controlled and the polydispersity was low. In the presence of pyridiniumm p-toluenesulfonate, carboxyl groups on the poly(AA-co-MMA) chains reacted with bis[4-(vinyloxy)butyl](4-methy1-1,3-phenylene)biscarbamate generating a copolymer network with hemiacetal component in the crosslinking segment. After being treated in strong acid, the polymer network exhibited degradable capability due to the hemiacetal structure, but the backbone chains of poly(AA-co-MMA) remained intact.Maleic anhydride (MAn) and styrene (St) were copolymerized in1,4-dioxane with2,2’-azobisisobutyronitrile as initiator and2-(ethoxycarbony-1)prop-2-yl dithiobenzoate as RAFT agent, synthesizing a block copolymer P(MAn-alt-St)m-b-(St)n. The molecular weight of P(MAn-alt-St)m-b-(St)n was well-controlled and the polydispersity was low. A series of block copolymers for different m/n were obtained by changing the feeding ratio of MAn and St. In alkali aqueous solution the copolymers were hydrolyzed, generating amphiphilic copolymers and performing self-assemble behavior. The hydrolyzed copolymers were used as macromolecular emulsifier and presented different capability in emulsion polymerization according to m/n.Maleic anhydride (MAn) and n-butyl vinyl ether (n-BVE) were copoly-merized in1,4-dioxane with2,2’-azobisisobutyronitrile as initiator and2-(eth-oxycarbonyl)prop-2-yl dithiobenzoate as RAFT agent, synthesizing an alterna- ting copolymer P(MAn-alt-BVE). Yet the molecular weight of copolymer was not well-controlled and the polydispersity was broad, indicating that the RAFT agent possesses an invisible capability in controlling the polymerization process of MAn and n-BVE.Diphenylmethane diisocyanate and4-hydroxybutyl vinyl ether underwent an addition reaction generating a divinyl ether bis[4-(vinyloxy)butyl](4-meth-yl-1,3-phenylene)biscarbamate (BECT) with crosslinker group (CH2=CH-O-) at both sides. The reaction was carried in mild condition with a high yield. BECT was reacted with acrylic acid/2-hydroxyethyl methacrylate, synthesiz-ing a crosslinker bis[4-(1-acryloyloxy)ethoxy butyl](methylenedi-4,1-phenyl-ene) biscarbamate (BABE)/bis{4-[1-(2-methacryloyloxy)ethoxy]ethoxy butyl}(methylenedi-4,1-phenylene)biscarbamate (BMBE) with (hemi)acetal compo-nent in the molecular structure. The solution or suspension polymerization of methyl methacrylate (MMA) was operated with the crosslinker BABE/BMBE, generating a polymer gel or gel particles that exhibited degradable capability in acid.Maleic anhydride (MAn), n-butyl vinyl ether (n-BVE) and4-hydroxybut-yl vinyl ether (HBVE) were copolymerized in tetrahydrofuran with2,2’-azo-bisisobutyronitrile as initiator, synthesizing an alternating copolymer P((MAn-alt-BVE)-co-(MAn-alt-HBVE)). In the presence of pyridinium p-toluenesul-fonate, hydroxyl groups from HBVE unit reacted with bis[4-(vinyloxy)butyl](4-methyl-1,3-phenylene)biscarbamate generating a copolymer network with acetal component in the crosslinking segment. Treated in strong acid, the polymer network exhibited degradable capability due to the acetal structure.