Slow Relaxation of Spin-Cast Poly(methyl methacrylate) Confined in Thin Films

Abstract

Although the volume relaxation of bulk homopolymer glasses is thoroughly understood, many questions remain about the volume relaxation of polymers cast from solvent. Furthermore, in polymer thin films, the possible effects of confinement, surfaces and interfaces on relaxation are largely unexplored. Measurements of the film thickness of spin-cast poly(methyl methacrylate) thin films over extended periods of time, using spectroscopic ellipsometry, reveal that the characteristic time for relaxation increases with film thickness. This result is consistent with the idea of enhanced molecular mobility in thin films, and it might reflect the conformation and a reduced extent of entanglements of the polymers when spin-cast from dilute solution.

Thickness and Substrate Dependences of the Relaxation of Spin-Coated Polymethyl Methacrylate Ultrathin Films Supported on SiO2 and SiOH Substrates

“…Since the structural relaxation proceeds slower than the glass transition, finer details of the mechanism can be deduced from the former. Despite the growing literature on the confinement effect in glass-forming thin polymer films, a comprehensive understanding of the relaxation process in polymers that are confined in a quasi-2-D geometry has not been acquired . It is thus beneficial to conduct more studies with ultrathin-film systems to understand the anomalous nature of relaxation in supported polymer systems.…”