Sarangapani Prasad S, Yu Yanghai, Zhao Jiang, Zhu Yingxi
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 1):061406. doi: 10.1103/PhysRevE.77.061406. Epub 2008 Jun 30.
The physical mechanism of colloidal gelation remains inadequately understood, particularly for intermediate to high volume fractions. Experiments to directly probe the complex evolution of structural and viscoelastic properties of gels have been few despite their fundamental importance in elucidating the physical mechanisms responsible for gelation. In this study, we use a home-built micron-gap rheometer combined with confocal microscopy to directly investigate the coupled structural and dynamic properties of colloidal gelation transition by spatial confinement. We observe that confinement-induced gelation proceeds by a spinodal decomposition route where strongly confined colloidal suspensions evolve into "colloid-rich" and "colloid-poor" regions; the propagation of the "colloid-rich" region in three dimensions is responsible for structural arrest and strong viscoelastic enhancement when a critical film thickness approaches 16-25 particle layers.
胶体凝胶化的物理机制仍未得到充分理解，特别是对于中等至高体积分数的情况。尽管直接探测凝胶结构和粘弹性性质的复杂演变对于阐明导致凝胶化的物理机制至关重要，但相关实验却很少。在本研究中，我们使用自行搭建的微米级间隙流变仪结合共聚焦显微镜，通过空间限制直接研究胶体凝胶化转变过程中的结构和动力学耦合特性。我们观察到，限制诱导的凝胶化通过旋节线分解途径进行，其中强限制的胶体悬浮液演变为“富胶体”和“贫胶体”区域；当临界膜厚度接近16 - 25个颗粒层时，“富胶体”区域在三维空间中的传播导致结构停滞和强粘弹性增强。
