Colloidal system to explore structural and dynamical transitions in rod networks, gels, and glasses.
Colloidal system to explore structural and dynamical transitions in rod networks, gels, and glasses.
复制标题
用于探索棒网络、凝胶和玻璃中的结构和动力学转变的胶体系统。
作者：
G. Wilkins;P. Spicer;M. Solomon
我们介绍了一个模型系统，由自组装的聚酰胺各向异性胶体悬浮在表面活性剂水溶液中的棒状网络，凝胶和玻璃的动力学研究。该胶体颗粒通过在59至100 ℃的温度下从水性表面活性剂相中重结晶聚酰胺而形成。从T=59 ° C到T=100 ° C，纵横比随温度单调增加，并且形成纵横比r=8+/-1到r=306+/-14的杆。我们通过共聚焦激光扫描显微镜和动态光散射表明，随着体积分数的增加，从具有扩散动力学的稀棒行为到具有越来越慢的动力学的均匀网络结构的结构转变。此外，增加杆的纵横比诱导从稀杆行为到网络结构的类似结构转变，尽管在较低的体积分数下。最后，我们通过聚合物诱导的耗尽相互作用改变棒之间的对势，从而观察到意外的网络到束的转变。束是几个棒直径宽和1-2棒长度。在每一束中，视杆似乎按向列排列。成束转变导致悬浮液的储能模量降低一个数量级。研究结果可应用于复杂流体稳定化以及杆凝胶化和玻璃化的基础研究的发展战略。
We introduce a model system consisting of self-assembled polyamide anisotropic colloids suspended in an aqueous surfactant solution for studies of the dynamics of rod networks, gels, and glasses. The colloidal particles are formed by recrystallization of a polyamide from an aqueous surfactant phase at temperatures from 59 to 100 degrees C. The aspect ratio increases monotonically with temperature from T=59 degrees C to T=100 degrees C and rods with an aspect ratio r=8+/-1 to r=306+/-14 form. We show by confocal laser scanning microscopy and dynamic light scattering a structural transition from dilute rod behavior with diffusive dynamics to a homogeneous network structure with increasingly slow dynamics as the volume fraction is increased. Furthermore, increasing the aspect ratio of rods induces a similar structural transition from dilute rod behavior to a network structure, although at a lower volume fraction. Finally, we vary the pair potential between the rods by a polymer-induced depletion interaction and thereby observe an unexpected network-to-bundle transition. The bundles are several rod diameters wide and 1-2 rod lengths long. The rods appear to be ordered nematically within each bundle. The bundling transition leads to an order of magnitude decrease in the storage modulus of the suspensions. The results can be applied to develop strategies for complex fluid stabilization as well as for fundamental studies of rod gelation and vitrification.