Sprakel Joris, van der Gucht Jasper, Cohen Stuart Martien A, Besseling Nicolaas A M
Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, HB Wageningen, The Netherlands.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 1):061502. doi: 10.1103/PhysRevE.77.061502. Epub 2008 Jun 3.
We discuss the thermal motion of colloidal particles in transient polymer networks. For particles that are physically bound to the surrounding chains, light-scattering experiments reveal that the submillisecond dynamics changes from diffusive to Rouse-like upon crossing the network formation threshold. Particles that are not bound do not show such a transition. At longer time scales the mean-square displacement (MSD) exhibits a caging plateau and, ultimately, a slow diffusive motion. The slow diffusion at longer time scales can be related to the macroscopic viscosity of the polymer solutions. Expressions that relate the caging plateau to the macroscopic network elasticity are found to fail for the cases presented here. The typical Rouse scaling of the MSD with the square root of time, as found in experiments at short time scales, is explained by developing a bead-spring model of a large colloidal particle connected to several polymer chains. The resulting analytical expressions for the MSD of the colloidal particle are shown to be consistent with experimental findings.
我们讨论了瞬态聚合物网络中胶体粒子的热运动。对于物理上与周围链结合的粒子，光散射实验表明，在跨越网络形成阈值时，亚毫秒动力学从扩散转变为类Rouse运动。未结合的粒子则不会出现这种转变。在更长的时间尺度上，均方位移（MSD）呈现出一个笼蔽平台，最终是缓慢的扩散运动。较长时间尺度上的缓慢扩散可能与聚合物溶液的宏观粘度有关。对于此处给出的情况，发现将笼蔽平台与宏观网络弹性相关联的表达式并不适用。在短时间尺度实验中发现的MSD随时间平方根的典型Rouse标度，通过建立一个连接到几条聚合物链的大胶体粒子的珠簧模型得到了解释。所得到的胶体粒子MSD的解析表达式与实验结果一致。
