Direct observation of mobility of thin polymer layers via asymmetric interdiffusion using neutron reflectivity measurements

Megumi Ooe; Kairi Miyata; Jun Yoshioka; Koji Fukao; Fumiya Nemoto; Norifumi L Yamada

doi:10.1063/1.5132768

Direct observation of mobility of thin polymer layers via asymmetric interdiffusion using neutron reflectivity measurements

J Chem Phys. 2019 Dec 28;151(24):244905. doi: 10.1063/1.5132768.

Authors

Megumi Ooe¹, Kairi Miyata¹, Jun Yoshioka¹, Koji Fukao¹, Fumiya Nemoto², Norifumi L Yamada²

Affiliations

¹ Department of Physics, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu 525-8577 Japan.
² Neutron Science Division, Institute for Materials Structure Science, High Energy Acceleration Research Organization, 203-1 Shirakata, Tokai, Naka 319-1106, Japan.

PMID: 31893884
DOI: 10.1063/1.5132768

Abstract

In this study, we investigated the diffusion dynamics at the interface between deuterated poly(methyl methacrylate) (d-PMMA) and protonated poly(methyl methacrylate) (h-PMMA) in two-layered thin films of d- and h-PMMA layers via neutron reflectivity (NR) measurements during isothermal annealing above the glass transition temperature T_g. When T_g of d-PMMA was higher than that of h-PMMA, the d-PMMA layer thickness increased with increasing annealing time t_a and, simultaneously, the h-PMMA layer thickness decreased. However, the opposite t_a dependence of the layer thicknesses was observed, if the T_g of d-PMMA was decreased by the increase in the fraction of the low-molecular weight d-PMMA: With increasing t_a, the d-PMMA layer thickness decreased and the h-PMMA layer thickness increased when T_g of d-PMMA was lower than that of h-PMMA. This change in the t_a dependence of the layer thickness was related to the change in the mobility of the d-PMMA layer accompanied by the change in the T_g value of d-PMMA. With the decrease in the d-PMMA layer thickness from 49 nm to 13 nm, when the h-PMMA layer thickness was maintained, the t_a dependence of the layer thickness changed and the mobility of the d-PMMA layer dramatically increased. These results suggest that the mobility of thin polymer films can be determined by the observation of interfacial dynamics via NR measurements.