In-Plane Movement of Isolated Poly(methacrylate) Chains on a Hydrophilic Solid Surface

A better understanding of the dynamic behavior of polymer chains on solid surfaces is indispensable for the design and construction of high-performance polymer composites. We herein visualized the in-plane movement of isolated poly(methyl methacrylate) (PMMA) and poly(tert-butyl methacrylate) (PtBMA) single chains on hydrophilic silicon wafers under ambient conditions by atomic force microscopy. Isolated PMMA chains adsorbed to the substrate, whereas PtBMA chains diffused, the degree of which was dependent on the humidity. Neutron reflectivity revealed the formation of a layer of condensed water on the substrate. All-atomistic molecular dynamics simulations implied that the diffusivity difference of the two polymers was based on the submerged depth in which a part of a chain existed. That is, the interaction of a polymer with the surface of the hydrophilic substrate primarily governs its lateral movement, or adsorption behavior, facilitated by the presence of water.