Investigate the Glass Transition Temperature of Hyperbranched Copolymers with Segmented Monomer Sequence

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• 作者：Yi Shi ; Xiaosong Cao ; Shuangjiang Luo ; Xiaofeng Wang ; Robert W. Graff ; Daqiao Hu ; Ruilan Guo ; Haifeng Gao
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：June 28, 2016
• 年：2016
• 卷：49
• 期：12
• 页码：4416-4422
• 全文大小：405K
• 年卷期：0
• ISSN：1520-5835

文摘

Hyperbranched copolymers with segmented structures were synthesized using a chain-growth copper-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization via sequential monomer addition in one pot. Three AB₂-type monomers that contained one alkynyl group (A), two azido groups (B), and one dangling group, either benzyl or oligo(ethylene oxide) (EO_x, x = 3 and 7.5), were used in these CuAAC reactions. Varying the addition sequences and feed ratios of the monomers produced a variety of hyperbranched copolymers with tunable compositions, molecular weights, segmented structures, and consequently glass transition temperature (T_g). It was found that the T_g of hyperbranched copolymers was little affected by the polymer molecular weights when M_n ≥ 5000. However, the values of T_g were significantly determined by the compositions of the terminal groups and the outermost segment of the hyperbranched copolymers. The last added AB₂ monomer in the polymerization formed an outermost “shell” and shielded the contribution of inner segments to the glass transition of the copolymers, reflecting a chain sequence effect of hyperbranched polymers on the thermal properties.