English Abstract

Dynamics of Rubbery Chains at a Model Filler Interface

Department of Applied Chemistry, Kyushu University, Nishi-ku Fukuoka, Japan
Nippon Gomu Kyokaishi,(2019),92(9),357-362 General Review in Japanese

The rotational relaxation time of a fluorescent molecule dispersed in rubbery polymers was characterized by time-resolved fluorescence anisotropy (TRFA) measurement and an attempt was made to quantitatively combine it with the segmental relaxation time of the corresponding polymer obtained by dielectric relaxation spectroscopy. Then, we show that the segmental relaxation time extrapolated to higher temperatures using the Vogel-Fulcher-Tammann law could be superimposed on the rotational relaxation time, resulting in a single curve. This behavior was common for polyisoprene and acrylonitrile/butadiene copolymer, implying that the rotational dynamics of a fluorescence probe is a useful tool for the characterization of polymer dynamics. Once this was established, TRFA was applied to a model filler interface combining with the evanescent wave excitation. Also, sum-frequency generation spectroscopy, which provides the best depth resolution among available techniques, was used. We found the presence of the dynamics gradient of chains in the interfacial region with the SiO2 surface and tried to assign it to the two kinds of adsorbed chains, namely loosely and strongly adsorbed, at the interface. The segmental relaxation of chains in the strongly adsorbed layer at the interface could be slower than that of bulk chains by more than 10 orders.

Keywords: Segmental Dynamics, Interface, Interfacial Sensitive Spectroscopy, Dielectric Relaxation Spectroscopy