Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, Staten Island, New York 10314, USA.
Soft Matter. 2018 May 23;14(20):4194-4203. doi: 10.1039/c8sm00080h.
The glassiness of polymer melts is generally considered to be suppressed by small dimensions, added solvent, and heat. Here, we suggest that glassiness persists at the nanoscale in worm-like micelles composed of amphiphilic diblock copolymers of poly(ethylene oxide)-polystyrene (PS). The glassiness of these worms is indicated by a lack of fluorescence recovery after photobleaching as well as micron-length rigid segments separated by hinges. The coarse-grained molecular dynamics studies probe the dynamics of the PS in these glassy worms. Addition of an organic solvent promotes a transition from hinged to fully flexible worms and to spheres or vesicles. Simulation demonstrates two populations of organic solvent in the core of the micelle-a solvent 'pool' in the micelle core and a second population that accumulates at the interface between the core and the corona. The stable heterogeneity of the residual solvent could explain the unusual hinged rigidity, but solvent removal during shear-extension could be more effective and yield - as observed - nearly straight worms without hinges.
聚合物熔体的玻璃态通常被认为受到小尺寸、添加溶剂和热量的抑制。在这里，我们提出在由两亲性嵌段共聚物聚（氧化乙烯）-聚苯乙烯（PS）组成的蠕虫状胶束中，纳米尺度上仍然存在玻璃态。这些蠕虫的玻璃态表现为光漂白后荧光恢复的缺乏以及由铰链分隔的微米长度的刚性段。粗粒分子动力学研究探测了这些玻璃状蠕虫中 PS 的动力学。添加有机溶剂会促进从铰链到完全柔性的蠕虫以及到球体或囊泡的转变。模拟表明，在胶束的核心中有两种有机溶剂的存在——一种是胶束核心中的溶剂“池”，另一种是在核心和冠之间的界面处积累的第二溶剂池。残留溶剂的稳定异质性可以解释异常的铰链刚性，但在剪切-拉伸过程中去除溶剂可能更有效，并产生——如观察到的——没有铰链的几乎笔直的蠕虫。
