Effect of the monomer structure on the dynamics of semidilute polyalkylmethacrylate solutions: A quasielastic light and neutron scattering investigation

The study of the microscopic origin of the slow relaxation modes in the autocorrelation functions of some entangled polymer solutions has recently given rise to much experimental and theoretical work. The aim is to highlight the role of concentration, molecular weight, and temperature on the slow modes and to what extent the entanglement phenomena are responsible for their appearance. The present work reports on the comparison between the dynamics of homologous polymers with different side unit lengths, by use of quasi-elastic light and neutron scattering. The investigation, carried out on both mesoscopic and microscopic scales, with different concentrations and chain lengths, evidenced different dynamical properties in the three polymer solutions. In particular, longer side chains give rise to a bigger volume excluded to the other segments, obstructing the entanglements responsible for the slow relaxation modes and favoring the mobility of segments. (C) 2002 American Institute of Physics.