A Vesicle-to-Worm Transition Provides a New High-Temperature Oil Thickening Mechanism.
A Vesicle-to-Worm Transition Provides a New High-Temperature Oil Thickening Mechanism.
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DOI：
10.1002/anie.201609365
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发表时间：
2017-02-06
期刊：
影响因子：
--
通讯作者：
Armes SP
中科院分区：
文献类型：
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作者：
Derry MJ;Mykhaylyk OO;Armes SP
通过RAFT分散聚合，直接在矿物油中制备了两嵌段共聚物微囊。根据透射电子显微镜和小角X射线能谱分析，这些囊泡在加热到150 °C时经历了从囊泡到虫子的转变。变温1H 核磁共振谱表明，这一转变是热溶剂对成膜嵌段进行表面增塑的结果，有效地增加了稳定嵌段的体积分数，从而降低了共聚物链的堆积参数。10 %w/w共聚物在矿物油中的分散液流变行为强烈依赖于温度：当加热超过临界凝胶化温度135时，储存模数增加五个数量级，因为不相互作用的囊泡转变为弱相互作用的蠕虫。SAXS研究表明，平均每个囊泡形成三条蠕虫。这种从囊泡到蠕虫的转变为油的高温增稠提供了一种有趣的新机制。
Diblock copolymer vesicles are prepared via RAFT dispersion polymerization directly in mineral oil. Such vesicles undergo a vesicle‐to‐worm transition on heating to 150 °C, as judged by TEM and SAXS. Variable‐temperature 1H NMR spectroscopy indicates that this transition is the result of surface plasticization of the membrane‐forming block by hot solvent, effectively increasing the volume fraction of the stabilizer block and so reducing the packing parameter for the copolymer chains. The rheological behavior of a 10 % w/w copolymer dispersion in mineral oil is strongly temperature‐dependent: the storage modulus increases by five orders of magnitude on heating above the critical gelation temperature of 135 °C, as the non‐interacting vesicles are converted into weakly interacting worms. SAXS studies indicate that, on average, three worms are formed per vesicle. Such vesicle‐to‐worm transitions offer an interesting new mechanism for the high‐temperature thickening of oils.