Space-Dependent Dynamics in 1,4-Polybutadiene Nanocomposite

Abstract

Understanding the dynamics of the glass transition of polymers and molecular liquids has been a goal of physicists for more than a half-century. The nature of this transition is directly linked to the heterogeneity of the dynamics, reflected in spatial and temporal correlations of molecular motions, as well as a distribution of relaxation times. 1−4 The former can be quantified by a dynamic correlation length that grows on approaching the glassy state and the latter from the breadth of the relaxation function or dynamic susceptibility. The majority of experimental studies of this topic rely on dielectric spectroscopy, which provides relaxation spectra over many decades of frequency. However, the higher order susceptibilities involving both spatial and temporal correlations cannot be obtained from linear relaxation measurements without assumptions. 5 Characterizing the spatial distribution of the dynamics requires other methods. Since the 1990s quasi-elastic neutron scattering (QENS) has been widely employed to obtain space-specific information on the dynamic properties, providing momentum (Q )a nd frequency dependences from the double differential scattering function of protons. 6 The Q-dependent scattering from glassforming materials can be described using the Kohlrausch− Williams−Watts (KWW) equation 7−11 τ Φ∝