A micellar sphere-to-cylinder transition of poly(ferrocenyldimethylsilane-b-2-vinylpyridine) in a selective solvent driven by crystallization
A micellar sphere-to-cylinder transition of poly(ferrocenyldimethylsilane-b-2-vinylpyridine) in a selective solvent driven by crystallization
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DOI：
10.1021/ma702852j
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发表时间：
2008-06-24
期刊：
影响因子：
5.5
通讯作者：
Winnik, Mitchell A.
中科院分区：
文献类型：
--
作者：
Shen, Lei;Wang, Hai;Winnik, Mitchell A.
一个poly(ferrocenyldimethylsilane)-b-poly(2-vinylpyridine)(PFS23-b-P2VP230)的样品具有较短的PFS嵌段和聚合度高10倍的P2VP嵌段，当溶解在乙醇中时，形成球形胶束。随着时间的推移(几小时、几天和几周)，这些溶液经历胶束球体到圆柱体的转变，最终形成相当坚硬、均匀的纤维状胶束，其芯宽为10 nm，长度在20至50微米之间，每个螺母长度约为4个聚合物分子。在这里，我们报告了结合透射电子显微镜、广角X射线散射(WAXS)以及静态和动态激光光散射测量的结果，以跟踪结构的演变。一个关键的观察结果是，在最初的诱导期(小时)之后，球形胶束开始部分聚集，因此，随着时间的推移，体系由自由球形胶束、胶束聚集体和具有高纵横比的细长结构的混合物组成。另一个重要的观察结果是，随着柱状胶束的数目和均匀性的增加，结晶PFS结构域的WAXS峰特征的强度和锐度也随之增加。这种结晶域的形成可能是结构转变的驱动力。
A sample of poly(ferrocenyldimethylsilane)-b-poly(2-vinylpyridine) (PFS23-b-P2VP(230)), with a short PFS block and a P2VP block 10-fold higher in degree of polymerization, forms spherical micelles when dissolved in ethanol. Over time (hours, days, and weeks), these solutions undergo a micelle sphere-to-cylinder transition eventually forming rather stiff, uniform fiber-like micelles with a core width of 10 nm, lengths between 20 and 50 mu m, and approximately four polymer molecules per nut length. Here, we report the results of a combination of transmission electron microscopy, wide-angle X-ray scattering (WAXS), as well as static and dynamic laser light scattering measurements to follow the structural evolution. One key observation is the onset of partial aggregation of spherical micelles after an initial induction period (hours), so that the system as it ages consists of mixtures of free spherical micelles, micelle aggregates, and elongated structures with a high aspect ratio. Another important observation is the growth in intensity and sharpness of the WAXS peak characteristic of crystalline PFS domains as the number and uniformity of the cylindrical micelles increases. This formation of crystalline domains is the likely driving force for the structural transformation.