It is well-recognized that block copolymer self-assembly in solution typically produces spheres, worms or vesicles, with the relative volume fraction of each block dictating the copolymer morphology. Stimulus-responsive diblock copolymers that can undergo either sphere/worm or vesicle/worm transitions are also well-documented. Herein we report a new amphiphilic diblock copolymer that can form spheres, worms, vesicles or lamellae in aqueous solution. Such self-assembly behavior is unprecedented for a single diblock copolymer of fixed composition yet is achieved simply by raising the solution temperature from 1 °C (spheres) to 25 °C (worms) to 50 °C (vesicles) to 70 °C (lamellae). Heating increases the degree of hydration (and hence the effective volume fraction) of the core-forming block, with this parameter being solely responsible for driving the sphere-to-worm, worm-to-vesicle and vesicle-to-lamellae transitions. The first two transitions exhibit excellent reversibility but the vesicle-to-lamellae transition exhibits hysteresis on cooling. This new thermoresponsive diblock copolymer provides a useful model for studying such morphological transitions and is likely to be of significant interest for theoretical studies.

中文翻译：

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热敏性二嵌段共聚物的独特水性自组装行为

众所周知，嵌段共聚物在溶液中的自组装通常会产生球形，蠕虫或小泡，每个嵌段的相对体积分数决定了共聚物的形态。可以经历球形/蠕虫或囊泡/蠕虫转变的刺激响应性二嵌段共聚物也有详细记录。本文中，我们报道了一种新的两亲性二嵌段共聚物，它可以在水溶液中形成球形，蠕虫，囊泡或薄片状。这种自组装行为对于单一的固定组成的二嵌段共聚物来说是前所未有的，但只需将溶液温度从1°C（球形）提高到25°C（蠕虫）到50°C（囊泡）再提高到70°C（薄片）。加热会增加成芯块的水合度（并因此增加有效体积分数），该参数仅负责驱动球体到蠕虫，蠕虫到囊泡以及囊泡到薄片的转变。前两个跃迁表现出出色的可逆性，但囊泡到薄片的跃迁在冷却时表现出滞后作用。这种新的热敏性二嵌段共聚物为研究这种形态转变提供了有用的模型，并且可能对理论研究具有重大意义。