Synthesis Of Four-arm Star-Shaped Triblock Copolymers Based On PEO

In the field of polymer science, it is always attractive for polymer scientists to design and synthesize the copolymers with well-defined structures and investigate their physico-chemical properties.Thanks to the development of living polymerization, combining the living radical polymerization with ionic polymerization, some linear and nonlinear (such as star, comb-like, dendritic, hyperbranch) copolymers are synthesized. In these amphiphilic copolymers, poly(ethylene oxide) (PEO) is an important composition for its good solubility in both water and most organic solvents.That's why PEO was always considered as one of the blocks when polymer scientists design new copolymers.In this thesis, on the basis of reversible addition-fragmentation chain transfer polymerization, a series of four-arm star-shaped triblock copolymers were synthesized by combination RAFT with other living polymerization techniques,The main results have been obtained as follows:1.A serises of well-difined water-soluble four-arm star-shaped triblock copolymers poly(ethylene oxide)-b-poly(N-isopropyl-acrylamide)-b-poly(2-(dimethylamino) ethyl methacrylate) (PEO4-b-PNIPAAm4-b-PDAMEMA4) was designed and synthesized. First, the four-arm star-shaped PEO4 was prepared by anionic ring-opening polymeration (AROP) of EO.Second, the star-shaped polymer (PEO4) was esterified by reaction with S-1-Dodecyl-S'-(α,α'-dimethyl-α"-acetic acid)trithio-carbonate)(DDAT), Third, AIBN as initiator at 80℃,sequential RAFT of NIPAAm and DMAEMA.The final product and intermediate were characterized by1H-NMR and GPC in details, The structure and molecular weights of every segment of the star-shaped triblock copolymer were controllable, and the polydispersity was small.2.The amphiphilic four-arm star-shaped triblock copolymers poly(ethylene oxide)-b-polystyrene-poly(acrylic acid) (PEO4-b-PS4-b-PAA4) was successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and reversive addition-fragmentation chain transfer polymerization(RAFT).used (PEO-DDAT)4 as macro-RAFT agent, AIBN as initiator at 80℃,sequential RAFT of St and AA. The final product and intermediate were characterized by1H-NMR and GPC in details, The structure and molecular weights of every segment of the star-shaped triblock copolymer were controllable, and the polydispersity was low.