摘要
构建了两端修饰有疏水聚合物的纳米棒模型,利用布朗动力学模拟研究了其组装行为,考察了溶剂选择性、纳米棒长度和纳米棒浓度等因素对组装行为的影响.研究表明,纳米棒可发生类似于高分子聚合的组装行为,在大部分情况下,其动力学符合高分子逐步聚合原理.但是,当纳米棒浓度较高或聚合物溶解性较好时,纳米棒的增长难以用逐步聚合原理来描述.本研究工作阐明了纳米棒的类聚合组装动力学,可为一维多级有序结构的设计和制备提供思路.
Step-wise self-assembly is a promising strategy to construct assemblies with higher-level hierarchy and complexity. In this self-assembly, the primary assemblies can self-assemble into one-dimensional structures in a way similar to the synthesis of polymers. However, the questions such as whether the principle of polymerization can apply to the one-dimensional growth of the assemblies still need to be clarified. To address this question, Brownian dynamics simulation was used to investigate the self-assembly of the nanorods with two ends capped with hydrophobic polymers such as polystyrenes. In the Brownian dynamics simulation, the amphiphility was simulated by choosing different cutt-off distances of the Lennard-Jones potentials for the nanorods and polymers. It was found that the nanorods associated with each other into chain-like structures via end-to-end connection, due to the hydrophobility of the polymers. The effects of the solvent selectivity, the length of the nanorods, and the concentration of the nanorods on the self-assembly were examined. The self-assembly of the nanorods into chain-like structures resembles the covalent polymerization of the monomers. The kinetics of the polymerization follows the rule of the step-growth polymerization in most of the cases. As the length of the nanorods or the concentration of the nanorods increases, the degrees of the polymerization show a more rapid increase as a function of time. For the effect of the solvent selectivity, the nanorods are found to be "polymerized"more rapidly as the solubility of the polymers decreases. However, as the solubilty of the polymers is low enough,the "polymerization" behavior is remarkedly less influenced by the solvent selectivity. Note that the rule of the step-growth polymerization cannot apply to the one-dimensional self-assembly of the nanorods when the concentration of the nanorods or the solubility of the polymer is higher. In addition, we found that the nanorods can self-assemble into ring-like structures with various numbers of nanorods via designing nanorods with adjustable chamfers at two ends. The observations are well consistent with some available experimental findings regarding the self-assembly of gold nanorods coated with a bilayer of cetyl trimethyl ammonium bromide along its sides and thiol-terminated polystyrene at two ends. The work can help to understand the dynamics of the selfassembly and designing one-dimensional ordered microstructures in future.
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