Dynamics of glass-forming polymers

At large length scales, polymers show typical soft matter properties, whereas glass-forming system features prevail at local scales. An intriguing dynamical complexity is thus inherent to these materials. With space-time resolution in a wide momentum transfer range, neutron scattering (NS) is a specially well-suited technique for unraveling dynamical processes in glass-forming polymers, since three correlation functions are accessible: the self motion of hydrogens, the collective motion involving deuterons and carbons and the single chain dynamic structure factor. In this work, we show how NS techniques have allowed to gain insight in the processes taking place at different length scales, like the entropy-driven dynamics and the structural relaxation, through the investigation of these correlators. In particular, the dynamical behavior in the unexplored intermediate length scales region, i.e., spatial scales of several times the typical interchain distances, is addressed. There, the microscopic details of the polymer begin to play a decisive role and induce deviations from the purely entropy-determined evolution of the single-chain dynamic behavior at large length scales. (C) 2004 Elsevier B.V. All rights reserved.