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

• Published in: The Journal of chemical physics Vol. 151; no. 24; p. 244905
• Main Authors: Ooe, Megumi, Miyata, Kairi, Yoshioka, Jun, Fukao, Koji, Nemoto, Fumiya, Yamada, Norifumi L
• Format: Journal Article
• Language: English
• Published: United States 28.12.2019
• ISSN: 1089-7690
• DOI: 10.1063/1.5132768

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 . When T of d-PMMA was higher than that of h-PMMA, the d-PMMA layer thickness increased with increasing annealing time t and, simultaneously, the h-PMMA layer thickness decreased. However, the opposite t dependence of the layer thicknesses was observed, if the T of d-PMMA was decreased by the increase in the fraction of the low-molecular weight d-PMMA: With increasing t , the d-PMMA layer thickness decreased and the h-PMMA layer thickness increased when T of d-PMMA was lower than that of h-PMMA. This change in the t 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 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 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.