The Glass-Transition Temperature of Supported PMMA Thin Films with Hydrogen Bond/Plasmonic Interface

The interfacial effect is one of the significant factors in the glass-transition temperature (T_g) of the polymeric thin film system, competing against the free surface effect. Herein, the T_gs of poly (methyl methacrylate) (PMMA) films with different thicknesses and substrates are studied by fluorescence measurements, focusing on the influence of interfacial effects on the T_gs. The strong interaction between PMMA and quartz substrate leads to increased T_gs with the decreased thickness of the film. The plasmonic silver substrate causes enhanced fluorescence intensity near the interface, resulting in the delayed reduction of the T_gs with the increasing film thickness. Moreover, as a proof of the interface-dependent T_gs, hydrogen bonds of PMMA/quartz and molecules orientation of PMMA/silver are explored by the Raman spectroscopy, and the interfacial interaction energy is calculated by the molecular dynamics simulation. In this study, we probe the inter-relationship between the interfacial interactions arising from the different substrates and the T_g behavior of polymer thin films.