Photon correlation spectroscopy of crosslinked polystyrene networks in the swollen state: Influence of macromolecular polydispersity

Abstract

AbstractWe report measurements of the correlation function of light scattered from thermally excited longitudinal fluctuations in crosslinked polystyrene networks at equilibrium. In order to investigate the influence of the polydispersity of linear chain elements between successive branch points, we synthesized a network by means of anionic block copolymerization, using a mixture of two “precursor” polystyrenes of different molecular weights to initiate polymerization of a small amount of divinyl‐benzene (DVB). The correlation function for fluctuations having a wave vector K, has the form of an exponential decay, exp (−Γ). The decay rate is given by Γ = D′K2, where D′ represents the diffusion constant of longitudinal modes of the network. We also present measurements of the correlation function of light scattered from gels prepared by anionic block copolymerization of styrene and DVB with only one “precursor” polystyrene and by a free‐radical process. In the latter case, the gels should have a wide distribution of linear chain lengths between branch points.