Dynamics Gradient of Polymer Chains near a Solid Interface

The relaxation dynamics of polyisoprene (PI) and nitrile butadiene rubber (NBR) chains at the SiO₂ interface were directly probed as a function of distance from the SiO₂ surface using time-resolved evanescent wave-induced fluorescence anisotropy, dielectric relaxation spectroscopy, and sum-frequency generation spectroscopy. 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.