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Glass Transition Temperature of Cyclic Stars

机译：循环星的玻璃化转变温度

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Cyclic homo- and diblock copolymers with different topologies were synthesized using a combination of "living" radical polymerization and "click" coupling reactions. The topologies included 2- and 3-arm stars, with the arms consisting of either cyclic or linear polystyrene. In addition, a diblock consisting of a cyclic polystyrene and a cyclic poly(acrylic acid) was also made. The topologies by imposing topological constraints due to the presence of cyclic polymers and branch points had a marked influence on the glass transition temperature (T-g. It was found that for the polystyrene topology series, the T-g increased above the glass transition temperature at infinite molecular weight for a linear chain (i.e., T-g(infinity)) and correlated to the more compact nature of cyclic polymers. For the cyclic diblock of polystyrene and poly(acrylic acid), the T-g increased significantly due to separation of the blocks into their pure phases. This resulted in significant stretching of the chains and thus loss of conformation entropy.
机译：使用“活性”自由基聚合和“点击”偶联反应的组合合成具有不同拓扑的环状均嵌段和二嵌段共聚物。拓扑包括2臂和3臂星形，其中的臂由环状或线性聚苯乙烯组成。另外，还制备了由环状聚苯乙烯和环状聚丙烯酸组成的二嵌段。通过存在环状聚合物和支化点而施加拓扑约束的拓扑结构对玻璃化转变温度（Tg）有显着影响。发现对于聚苯乙烯拓扑系列，在无限大分子量下，Tg升高到玻璃化转变温度之上。对于线性链（即，Tg（无穷大）），并且与环状聚合物的更紧密的性质相关。对于聚苯乙烯和聚丙烯酸的环状二嵌段，由于嵌段分离成纯相，Tg显着增加这导致链的显着拉伸，并因此丧失构象熵。

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