Metastable Polymer Adsorption Dictates the Dynamical Gradients at Interfaces

Polymer adsorption proceeds through a wide variety of metastable states due to kinetic constraints originating from the pinning of segments on solid interfaces, creating an interfacial adsorption layer composed of flattened trains, loosely adsorbed loops, and tails of chains. In this work, we show that the metastable structures of adsorption layers developed via thermal annealing at a temperature above glass-transition temperature Tg determine the length scale of interfacial mobility gradient dynamics (ξdyn). Specifically, we find that 1) the evolution of ξdyn mimics the trend in the slow kinetics of polymer absorption and 2) ξdyn grows linearly with the thickness of the overall interfacial adsorption layer. The findings reinforce the idea that the interfacial dynamical gradients are relevant to polymer adsorption and also imply that extension of the loosely adsorbed chains into the film interior could facilitate the propagation of suppressed dynamics originating at the interface.