Facile Synthesis of Hyperbranched and Star-Shaped Polymers by RAFT Polymerization Based on a Polymerizable Trithiocarbonate

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• 作者：Chengbo Zhang ; Yuan Zhou ; Qiang Liu ; Shixian Li ; Se虂bastien Perrier ; Youliang Zhao
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：April 12, 2011
• 年：2011
• 卷：44
• 期：7
• 页码：2034-2049
• 全文大小：1175K
• 年卷期：v.44,no.7(April 12, 2011)
• ISSN：1520-5835

文摘

Facile synthesis of hyperbranched and star polymers on the basis of S-(4-vinyl)benzyl S鈥?propyltrithiocarbonate (VBPT) was described. RAFT copolymerization of VBPT with vinyl monomers such as methyl methacrylates (MMA), styrene (St), methyl acrylate (MA), and tert-butyl acrylate (tBA) afforded hyperbranched copolymers with variable branch length and degree of branching. Hyperbranched copolymers obtained at a low feed ratio of vinyl monomers to VBPT usually possessed repeat units per branch higher than the expected values due to the presence of VBPT unit with pendant trithiocarbonate group and side reactions resulting in partial loss of CTA functionality. RAFT copolymerization at various feed ratios afforded poly(VBPT-co-MA) branched copolymers with weight-average CTA functionality up to 107 or more, which were further used to generate star PSt and PtBA with adjustable molecular weight and variable polydispersity (1.12 < PDI < 1.88). The approach based on two successive RAFT processes is general and versatile to synthesize multiarm star polymers with controllable arm length. The resultant polymers were characterized by ¹H NMR, GPC-MALLS, DSC, and TGA. The intrinsic viscosities of branched and star-shaped polymers were lower than those of their linear analogues with the same molecular weights; both Mark鈭扝ouwink鈭扴akurada exponent and contractor factor of branched copolymers were observed to increase with decreasing degree of branching, thus confirming a branching nature. The single glass transition temperature in DSC traces indicated branched copolymers obtained at various feed ratios had good compatibility.