Synthesis And Characteristics Of PVAc-containing Polymers By RAFT Polymerization

In this thesis, a novelω-azido-functionalized RAFT reagent, O-(2-azido-ethyl) S-benzyl dithiocarbonate (AEBDC), was firstly synthesized and subsequently employed to mediate the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc). Subsequently, theω-azido-terminated polymers (PVAc-N3) were coupled by"click"chemistry with a fluorescent alkyne to prepare fluorescent PVAc; and with other alkyne to modify PVAc. Furthermore, graft copolymers P (St-co-(p-CMS))-g-PVAc with controlled molecular weights and well-defined structures were synthesized by the combination of Stable Free Radical Polymerization (SFRP) with RAFT polymerization. Subsequently, the copolymers P(St-co-(p-CMS))-g-PVAc were hydrolyzed to obtain amphiphilic graft copolymers P(St-co-(p-CMS))-g-PVA. The obtained polymers were characterized by various techniques. The details were shown as follows:(1): Theω-azido-functionalized RAFT reagent (AEBDC) was employed to mediate the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc). The polymerization results showed that the RAFT polymerizations of VAc could be well controlled using AEBDC as the RAFT agent and a functional poly (vinyl acetate) (PVAc) with azido end-groups was obtained. Then theω-azido-terminated polymers were coupled by"click"chemistry with a fluorescent alkyne, 7-propinyloxy coumarin, to prepare fluorescent PVAc catalysted by a CuBr /PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) complex. The fluorescence properties of the PVAc homopolymers before and after coupling with 7-propinyloxy coumarin were investigated and showed that the fluorescence intensity of PVAc-1,2,3-triazole was higher than that of the 7-propinyloxy coumarin with the same concentration of coumarin moiety, indicating a strategy that the fluorescence intensity of polymers can be enhanced by"click"chemistry method. Moreover, theω-azido-terminated polymers were coupled by"click"chemistry with 1-Prop-2-ynyloxy-4-vinyl-benzene to prepare macromonomer.(2): Stable Free Radical Polymerization (SFRP) of styrene (St) and p-chloromethylstyrene (p-CMS) were firstly carried out using benzoyl peroxide (BPO) as the initiator to obtain the random copolymers of P(St-co-(p-CMS)). Subsequently, the random copolymers were converted into macro-RAFT agents through a simple method. Finally the macro-RAFT agents were used in the RAFT polymerization of vinyl acetate (VAc) to prepare graft copolymers P(St-co-(p-CMS))-g-PVAc with controlled molecular weights and well-defined structures. Furthermore, amphiphilic graft copolymers P(St-co-(p-CMS))-g-PVA were prepared by hydrolyzation of graft copolymers P(St-co-(p-CMS))-g-PVAc, and self-assembly behaviors of the obtained amphiphilic graft copolymers were primarily investigated .