Chain dynamics in spin-coated films of poly(methyl methacrylate) in a solvent annealing process

The dynamics of poly(methyl methacrylate) chains in spin-coating films during solvent annealing was studied. The neutron reflectometry (NR) measurement revealed that the absorbed solvent molecules homogeneously distributed in the spin-coated film and the solvent fraction increased to 0.35 in toluene vapor. From the real-time NR measurement for a stacked film of deuterated and hydrogenated PMMA in thermal annealing, the diffusion dynamics of the PMMA chain was strongly dependent on the distance from the surface: the polymer chain at the substrate was restricted. On the other hand, the depth dependence of the chain dynamics was weak in the spin-coated film in the solvent annealing process. Whereas the ratio of the diffusion constants of the PMMA chain at the surface and substrate was 50 in thermal annealing, the ratio in toluene vapor was as small as 2. Therefore, the solvent annealing provides sufficient mobility to the polymer chain near the substrate. This result indicates that the solvent annealing method enables the equilibration of a spin-coated polymer film from the surface to the substrate interface.