Assembly of Nanodispersed Key Lock Colloids Induced by Polymeric Depletants
Date Issued
2015
Date
2015
Author(s)
Huang, Chang-Wei
Abstract
Self-assembly has become the most common term for the autonomous aggregation over the past decade. In colloidal suspensions containing large and small particles a peculiar attraction force appears, which can lead to the aggregation of large particles. Especially, if a non-adsorbing polymer (depletant) is introduced into a colloidal system flocculation has often been observed. Recently, it is possible to experimentally synthesize a lock-like particle by producing a cavity on a spherical particle. The selectivity of binding between lock nanoparticles and the corresponding key nanoparticles induced by depletion force triggers wide discussion and investigation. In this thesis, we adopt dissipative particle dynamic (DPD) method to explore the depletion-induced self-assembled behavior between key and lock particles in the nanodispersed system. It is found that the lock-lock binding can be avoided by grafting polymers onto the convex side of the lock particles. The key-lock binding increases as the concentration and size of the depletants increase. Moreover, for a temperature responsive polymeric depletant, the size of the depletant varies with temperature and thus the binding capability of lock and key particles can be manipulated by adjusting temperature. Furthermore, it is observed that the geometric compatibility between key and lock particles is a crucial factor for lock-key binding. The degree of key-lock binding increases as the compatibility grows due to the significant increase in the overlapping of the excluded volume. Furthermore, we calculate depletion forces and binding energy between one pair of key and lock particles at different distances, and the binding fraction is consistent with the binding energy trend. Also, the binding volume can be derived via equilibrium constant. This consequence demonstrates that binding volume varies with geometric shapes resulting from different degree of rotational diffusivity of the key within the cavity. As the geometric compatibility between the key-lock binding is weak, the binding volume tends to grow due to the increase in the orientational rotation. Also, binding volume depends only on geometric shapes of the lock and key irrespective of the physical characteristics of the depletants. Our simulation results are in consistent with the experimental findings.
Subjects
Self-assembly
nanoparticles
colloids
Type
thesis
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