Adhesion of nanoparticles to polymer brushes studied with the ghost tweezers method.
Adhesion of nanoparticles to polymer brushes studied with the ghost tweezers method.
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DOI：
10.1063/1.4905894
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发表时间：
2015-01
期刊：
影响因子：
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通讯作者：
Jianli Cheng;A. Vishnyakov;A. Neimark
中科院分区：
文献类型：
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作者：
Jianli Cheng;A. Vishnyakov;A. Neimark
利用耗散粒子动力学模拟和模拟光学或磁性镊子实验室实验的一种独创的“幽灵镊子”方法，探索了纳米粒子(NPs)和聚合物刷子(PBS)之间的相互作用机理。采用鬼钳法计算了吸附自由能。幽灵镊子代表一个虚拟的谐波势，它用弹簧将NP系在给定的锚点上。平均弹簧力表示作为NP坐标函数的NP-PB相互作用的有效力。NP-PB相互作用的自由能图谱被计算为将NP从溶剂本体转移到距衬底表面特定距离所需的机械功。利用这一技术，我们探索了在丙酮-苯二元溶剂中，裸露的和配体功能化的球形纳米粒子与聚异戊二烯天然橡胶刷的粘附性。我们研究了NP-PB相互作用的两种基本机制，即NP在PB外部的附着和NP在PB中的浸入，这两种机制是由聚合物在NP表面的吸附和配体在衬底的吸附引起的熵排斥力和热引力之间的相互作用决定的。计算了不同接枝密度、不同NP尺寸和不同溶剂组成时，平衡粘附态的相对自由能和分离这些态的势垒。
Mechanisms of interactions between nanoparticles (NPs) and polymer brushes (PBs) are explored using dissipative particle dynamics simulations and an original "ghost tweezers" method that emulates lab experiments performed with optical or magnetic tweezers. The ghost tweezers method is employed to calculate the free energy of adhesion. Ghost tweezers represents a virtual harmonic potential, which tethers NP with a spring to a given anchor point. The average spring force represents the effective force of NP-PB interaction as a function of the NP coordinate. The free energy landscape of NP-PB interactions is calculated as the mechanical work needed to transfer NP from the solvent bulk to a particular distance from the substrate surface. With this technique, we explore the adhesion of bare and ligand-functionalized spherical NPs to polyisoprene natural rubber brush in acetone-benzene binary solvent. We examine two basic mechanisms of NP-PB interactions, NP adhesion at PB exterior and NP immersion into PB, which are governed by interplay between entropic repulsive forces and enthalpic attractive forces caused by polymer adsorption at the NP surface and ligand adsorption at the substrate. The relative free energies of the equilibrium adhesion states and the potential barriers separating these states are calculated at varying grafting density, NP size, and solvent composition.