Observing Thermal Motion for Isolated Poly(tert-butyl methacrylate) Chains on Solid Surfaces

A better understanding of the hierarchical dynamics of polymers on a solid surface is of pivotal importance for improving the material designs of polymer nanocomposites.  Here, we examined the thermal molecular motion of isolated poly(tert-butyl methacrylate) (PtBMA) chains on solid surfaces based on atomic force microscopy.  While the center-of-mass diffusion of chains was not clearly observed on the hydrophobic hydrogen-passivated silicon substrate, it was on the hydrophilic hydroxy-terminated silicon substrate.  The diffusion coefficient for chains on the hydrophilic substrate was (1.35 ± 0.08) x 10^-14 cm²•s^-1.  The mobility difference of PtBMA chains on the two substrates might be explained in terms of the presence or absence of adsorbed water molecules in addition to the interaction with the substrate.