Li Congcong, Zhang Tiancai, Yang Yingzi, Tang Ping, Qiu Feng
The State Key Laboratory of Molecular Engineering of Polymers, Key Laboratory of Computational Physical Sciences, Department of Macromolecular Science, Fudan University, Shanghai 200433, China.
ACS Omega. 2019 Jul 31;4(7):12927-12937. doi: 10.1021/acsomega.9b01800.
Polymer brushes have wide application in surface modification. We study dense, short polymer brushes immersed in a mixing solvent under athermal conditions using the classical density functional theory. The brush polymer is short so that the equilibrium behavior of the brush deviates far from the scaling laws for infinite brush chains. The excluded volume interaction is the only interaction in the system. We compare the excluded volume effect of solvent molecules of different shapes. Two types of mixing solvents are considered: solvent composed of linear oligomers and monomers, or that of spherical particles and monomers. The effects of grafting density, solvent molecular size, and solvent number density on the brush height, the density profiles, the relative excess adsorption, and the brush-solvent interface width are systematically analyzed. In the adsorption aspect, the spherical particles have stronger ability than the linear oligomers do to penetrate through the brush layer and gather at the substrate. In the screening aspect, the oligomers are more capable of screening the excluded volume interaction between the brush chains than the spherical particles. The brush-solvent interface width decreases monotonically with increasing oligomer length, but it has a minimum with the increasing spherical particle size. Our research differentiates the attractive-interaction-induced phenomenon and the volume-exclusion-induced phenomenon in dense brush systems and exhibits the difference in the antifouling properties of the brushes contacting solvent molecules of different shapes.
聚合物刷在表面改性方面有广泛应用。我们使用经典密度泛函理论研究了在无热条件下浸入混合溶剂中的致密短聚合物刷。刷聚合物很短，以至于刷的平衡行为与无限长刷链的标度律有很大偏差。排除体积相互作用是系统中唯一的相互作用。我们比较了不同形状溶剂分子的排除体积效应。考虑了两种类型的混合溶剂：由线性低聚物和单体组成的溶剂，或由球形颗粒和单体组成的溶剂。系统地分析了接枝密度、溶剂分子尺寸和溶剂数密度对刷高、密度分布、相对过量吸附以及刷 - 溶剂界面宽度的影响。在吸附方面，球形颗粒比线性低聚物更有能力穿透刷层并聚集在基底上。在屏蔽方面，低聚物比球形颗粒更能屏蔽刷链之间的排除体积相互作用。刷 - 溶剂界面宽度随低聚物长度增加单调减小，但随球形颗粒尺寸增加有一个最小值。我们的研究区分了致密刷系统中吸引相互作用诱导的现象和体积排除诱导的现象，并展示了与不同形状溶剂分子接触时刷的防污性能差异。
