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(g)s 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(g)s. The strong interaction between PMMA and quartz substrate leads to increased T(g)s 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(g)s with the increasing film thickness. Moreover, as a proof of the interface-dependent T(g)s, 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.