(600c) Molecular Dynamics Characterization of End Grafted Polymer Brushes: Equilibrium and Confined Brushes

Molecular dynamics simulations of a polar polymer brush in a polar solvent are presented using a coarse-grained approach. Chain extension is heavily influenced by temperature as expected. Chains extend far from the surface at high temperature, while surface adsorption at a weakly attractive surface dominates at low temperature. Increasing grafting density leads to greater chain extension due to excluded volume effects under all conditions, consistent with previous findings. Polymer depletion regions are found near the surface even at very high grafting densities indicating a chain orientation normal to the surface close to the grafting points. Radial distribution functions reveal that the grafting pattern does not affect the overall brush configuration beyond the first five monomers of each chain as long as the surface is homogeneously covered. Results will be presented for both a single unperturbed brush and two opposing brushes. The opposing brushes are examined under different degrees of static compression, beginning far enough away from each other such that they mimic the single brush structure. The separation distance between the two surfaces is subsequently decreased until the brushes substantially interact with one another. To examine the effect of compression mechanisms, a single brush is also compressed to the same degree by a bare surface and compared to the compression by a polymer brush.