Core cross-linked star-shaped poly(N-isopropylacrylamide) (PNIPAAm), which was prepared via an arm-first method by reversible addition-fragmentation chain-transfer polymerization, was shown to exhibit unique thermoresponsive behavior in water. Star polymers with ~20–35 arms with narrow molecular weight distributions apparently had a more hydrophilic nature compared with that of linear PNIPAAm, judging from their thermoresponsive behavior. Most importantly, an aqueous solution of the star PNIPAAm with carboxy ends remained transparent even at 70 °C.

中文翻译：

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热响应核心交联星形聚（N-异丙基丙烯酰胺）可逆和可控聚集纳米级分子单元

核心交联星形聚（N-异丙基丙烯酰胺）（PNIPAAm）是通过可逆加成-断裂链转移聚合通过臂优先方法制备的，在水中表现出独特的热响应行为。与线性 PNIPAAm 相比，具有约 20-35 个臂和窄分子量分布的星形聚合物显然具有更亲水的性质，从它们的热响应行为来看。最重要的是，即使在 70°C 下，具有羧基末端的星形 PNIPAAm 水溶液仍保持透明。