Radical Polymerization Of Chloroprene: Reversible-Deactivation Radical Polymerization And Irreversible Addition-Fragment Chain Transfer Polymerization

This dissertation was mainly focused on the reversible-deactivation radical polymerization and irreversible addition-fragment chain transfer polymerization for choroprene. The main contents are as follows:1. Reversible addition-fragmentation chain transfer (RAFT) polymerization of the reactive monomer chloroprene (2-chloro-1,3-butadiene, CP) mediated by ethyl 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate (EPDTB), 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPDTB), dibenzyl trithiocarbonate (DBTTC) and S-1-dodecyl-S’-(a,a’-dimethyl-a"-acetic acid)trithiocarbonate (DDAT) was investigated. The well-defined PCP homopolymers were synthesized, employing EPDTB and CPDTB as the RAFT-CTAs. However, DBTTC and DDAT were shown to be ineffective in RAFT polymerization of CP. We have demonstrated that the successful synthesis of PCP-based block copolymers by RAFT polymerization. The dithioester end-capped polystyrene was employed as a macro-CTA for the synthesis of diblock copolymer, PSt-b-PCP, employing EPDTB as the initial RAFT agent. Also, well-defined diblock copolymer PMMA-b-PCP has been successfully prepared through the RAFT polymerization using 2-cyano-2-propylbenzodithioate (CPDB) as the initial RAFT agent. Then, employing DBTTC as the molecular-weight regulator, chloroprene rubber (CR) was obtained through emulsion polymerization according to the reaction conditions of adhesive type CR-244. The performance of CR achieved a variety of standard industrial products.2. Degenerative transfer radical polymerization (DTRP) of CP mediated by iodoform (CHI3) and cyanopropyl iodide (CP-I) was investigated. The well-defined PCP homopolymers were synthesized. Also, well-defined diblock copolymers of PCP-b-PMMA, PCP-b-PSt, and PCP-b-PBA have been successfully prepared through the DTRP using CHI3 as the chain transfer agent.3. The reversible-deactivation radical polymerization (RDRP) of CP has been described using reverse iodine transfer polymerization (RITP) technique. Homopolymerization of CP was successfully performed in benzene at 50℃ using ABVN as radical initiator, where a molar ratio ABVN/I2= 1.7 was used. GPC and 1H NMR techniques were used to analyze the structure of the polymers. It was observed that RITP of CP proceed with controlled characteristics, so that products with predetermined molecular weight and a relatively narrow molecular weight distribution can be synthesized. Diblock copolymers of PCP-b-PSt and PCP-b-PMMA can also be successfully synthesized by sequential RITP of chloroprene followed by ITP of St and MMA, respectively.4. Two kinds of chain transfer agent, ethyl a-benzenesulfonyl-methylacrylate (EBSA), ethyl a-p-toluenesulfonyl-methacrylate (ETSA), were synthesized according to the literature. The chain transfer constants (Ctr) of EBSA and ETSA were determined in the bulk polymerization of CP. The emulsion polymerization of CP with EBSA and ETSA based on irreversible addition-fragmentation chain transfer (IAFCT) mechanism was carried out at 9 ℃. The effect of CTAs on the kinetics in the CP emulsion polymerization can be attributed to desorption of chain-transfered radicals from the polymer particles. EBSA decreased the reaction rate, which was attributed to serious desorption of chain-transfered radicals from the polymer particles. It has been described that ETSA with high Ctr provides the better balance between the rate of polymerization and the efficiency for molecular weight control than EBSA.