Comparing Attachment Methods of Surface Bound Chains and Their Impact on Local Glass Transition Dynamics

How polymer chains become bound to interfaces are fundamental to surface modification, adhesion, and reinforcement mechanisms. Efforts to investigate adsorbed chains in melt films and polymer nanocomposites frequently rely on solvent washing to expose such near-surface, "bound layer" chains. By comparing and contrasting surface bound chains in melts and solutions, 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 find that the adsorbed layer thickness remaining from the solvent rinsing of melt films 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. We compare how these different populations of surface bound chains alter the local glass transition temperature of neighboring polymer chains in bulk films, and compare them to end-tethered grafted chains.