Structure of the Poly(methyl methacrylate) Adsorbed Layer Determined by the Surface Chemistry of the Substrate

The adsorbed polymer layer on the inorganic solid surface is crucial in improving the physical properties of composite nanomaterials; therefore, the properties could be tuned by altering the structure of the adsorbed layer. We investigated poly(methyl methacrylate) (PMMA) adsorbed layers on SiO2–Si substrates by varying the hydroxyl (OH) group content on the substrate surface. The results indicated that the thicknesses of the flattened layer and loosely adsorbed layer decreased with decreasing OH group content and the flattened layer disappeared when the content was ∼31%. The OH groups controlled the formation of the adsorbed layer, providing anchor points through hydrogen bonding with the carbonyl groups in PMMA. With decreasing OH group content, fewer anchor points possibly prevented train conformation and the relatively stable loosely adsorbed chains still formed, which enhanced the segmental dynamics of the ultrathin PMMA film. These results provide novel insight into the role of surface chemistry in forming adsorbed polymer layers on substrates.