Characterization of High Grafting Density Polymer Brushes Using Molecular Dynamics Simulations and Experimental Methods.

摘要

Polymer brushes have the ability to modify surface properties for numerous applications. To better understand how they can be used, thorough characterization is necessary. Polymer brushes were studied from both a computational and experimental standpoint. The structure and interactions between two layers were examined, providing an understanding of how the systems respond to situations encountered in their applications.;A coarse-grained model for molecular dynamics simulations was used to allow larger system sizes and longer simulation times. The simulations first characterized the structure of a single brush in good solvent, examining polymer and solvent density profiles, radial distribution functions, chain orientation, and brush height.;Next, a method was developed to simulate confined polymer brushes using molecular dynamics with an explicit solvent. Density profiles and normal forces were measured for several levels of compression, and features in the force-distance profile were justified by looking at the corresponding density profiles. A significant correlation was observed between the degree of interpenetration of the brushes to the measured normal force.;Experimentally, polystyrene polymer brushes were synthesized using atomic transfer radical polymerization to create durable, very high grafting density layers. They were studied using a surface force apparatus to determine both normal force and frictional properties. The shear force experiments indicate that even at a very high grafting density, the polymer brushes provide a good lubricant for the surface.