Synthesis And Characterization Of Hyperbranched Polymers From Non-conjugated Monomers Via RAFT

Due to the unique performances of hyperbranched polymers, there was less entanglement between molecular chains. Thus branched polymers showed special properties: good solubility, low melting point and solution viscosity, and lower mechanical properties. Besides, they containing large amount of end groups, which was considered to have highly end-group reactivity. By modifying the end groups with functional groups, it would greatly enrich the types and applications of functional polymer materials. Non-conjugate vinyl monomer is the kind of monomer refers to the double bond with electronic groups, which including vinyl acetate (VAc), N-vinylcarbazole (NVC) and N-vinylpyrrolidone (NVP). As well known, RAFT polymerization of non-conjugate vinyl monomers mediated by xanthate proceeds in a''living''/controlled way, which termed as MADIX was the best approach. In this paper we synthesized two kinds of hyperbranched polymers by self-condensing vinyl polymerization (SCVP) combing with eversible addition-fragmentation chain transfer (RAFT) polymerization. Specific works were summarized as follows:(1) Reversible addition-fragmentation chain transfer (RAFT) polymerization of VAc in the presence of ECTVA, which capable of both reversible chain transferable through a xanthate moiety and propagation via a vinyl group, led to highly branched copolymers by a method analogous to self-condensing vinyl polymerization (SCVP). The ECTVA acted as a vinyl acetate AB* inimer. It was copolymerized with vinyl acetate (VAc) in ratios selected to tune the distribution and length of branches of resulting hyperbranched poly (vinyl acetate). The degree of branching increased with chain ECTVA concentration, as confirmed by NMR spectroscopy. The polymer structure was characterized via MALDI-TOF. Retention of the xanthate compound during the polymerization was evidenced by successful chain extension of a branched (PVAc) macroCTA by RAFT polymerization. The branched PVAc led to better dissolution as compared to linear PVAc, an effect attributed primarily to an increased contribution of end groups.(2) Reversible addition-fragmentation chain transfer (RAFT) polymerization of NVC in the presence of another AB* inimer called EVBCT, led to highly branched copolymers by a method analogous to self-condensing vinyl polymerization (SCVP). It was copolymerized with N-Vinylcarbazole (NVC) in ratios selected to tune the distribution and length of branches of resulting hyperbranched poly (N-Vinylcarbazole). Retention of the xanthate compound during the polymerization was evidenced by successful chain extension of a branched (PNVC) macroCTA by RAFT polymerization. The branched PNVC led to better dissolution as compared to linear PNVC, an effect attributed primarily to an increased contribution of end groups.