Comparison of Solution Grown and Film Washed Adsorbed Layers and Their Corresponding Impact on Film Dynamics

How the conformations and dynamics of surface bound chains influence neighboring chains are fundamental to adhesion and reinforcement mechanisms in polymer films and nanocomposites. Efforts to investigate adsorbed chains in melt films rely on solvent washing conditions to expose such near-surface chains. However, we find that the adsorbed layer thickness remaining from this protocol is entirely determined by the solvent washing conditions used, with only the time in solution needed to reach this final adsorbed amount affected by prior treatment of the melt film. These observations are consistent with surface diffusion and exchange measurements of adsorbed chains in solution demonstrating that surface bound chains are highly mobile, even for the case of strong adsorption. By directly comparing solution grown adsorbed layers with those formed by solvent washing melt films, we leverage the wealth of information on polymer adsorption in solution developed over several decades to inform us about polymer conformations in the melt. We investigate how these different populations of surface bound chains alter local glass transition properties of neighboring homopolymer chains, and compare them to end-tethered grafted chains.