Park Jun Dong, Ahn Kyung Hyun, Lee Seung Jong
School of Chemical and Biological Engineering, Institute of Chemical Process, Seoul National University, Seoul, 151-744, Korea.
Soft Matter. 2015 Dec 28;11(48):9262-72. doi: 10.1039/c5sm01651g.
The dynamics and rheological behavior of colloidal gels under oscillatory shear flow have been studied by using the Brownian dynamics simulations. The dynamics is studied under the oscillatory shear of small, medium, and large amplitudes. In the small amplitude oscillatory shear (SAOS) regime, the colloidal gel retains a rigid-chain network structure. The colloidal gel oscillates with small structural fluctuations and the elastic stress shows a linear viscoelastic response. In the medium amplitude oscillatory shear (MAOS) regime, the rigid network structure is ruptured, and a negative correlation between the absolute value of strain and the average bond number is observed. The elastic stress shows a transient behavior in between the SAOS and LAOS responses. In the large amplitude oscillatory shear (LAOS) regime, the colloidal gel shows a soft chain structure. Contrary to the negative correlation in the MAOS regime, the colloidal gel shows an oscillating dynamics with a positive correlation between the absolute value of strain and the average bond number. The soft chain structure exhibits no elasticity at small strain, while it shows strong elasticity at large strain. The oscillating dynamics and the rheological behavior are discussed in terms of the microstructural change from the rigid to soft chain structure.
通过布朗动力学模拟研究了胶体凝胶在振荡剪切流作用下的动力学和流变行为。在小、中、大振幅的振荡剪切作用下对动力学进行了研究。在小振幅振荡剪切（SAOS）区域，胶体凝胶保持刚性链网络结构。胶体凝胶以小的结构波动振荡，弹性应力表现出线性粘弹性响应。在中振幅振荡剪切（MAOS）区域，刚性网络结构破裂，观察到应变绝对值与平均键数之间存在负相关。弹性应力在SAOS和LAOS响应之间表现出瞬态行为。在大振幅振荡剪切（LAOS）区域，胶体凝胶呈现软链结构。与MAOS区域的负相关相反，胶体凝胶呈现振荡动力学，应变绝对值与平均键数之间存在正相关。软链结构在小应变时无弹性，而在大应变时表现出强弹性。从刚性到软链结构的微观结构变化方面讨论了振荡动力学和流变行为。
