Universal properties of polymer networks

Abstract

The use of thermodynamics of irreversible processes allows one to describe time dependent deformation phenomena of polymer networks. It is shown that linear relaxation modes are coupled to the network ("global level"). The constitutive van der Waals equation is characterized by a strain, strain-type and a strain-rate independent memory function. Stress-strain cycles in the glass-transition regime can be described.The dynamics of networks can be characterized by introducing the concept of conformons. Conformons are shown to be Bosons with a photon statistics. Conformons in equilibrium have a self-energy- and self-entropy-term. They can be excited or emitted. Conformons also decay spontaneously. In the stationary limit a broad conformon spectrum results which is typical for glass forming liquids (including polymers). Relaxation-and retardation-time spectra are shown to be related to the conformon spectrum. Mechanical and dielectric relaxation measurements (even of low molecular weight glass formers) are fairly well reproduced. The dynamical structure factors of the incoherent neutron scattering can also be computed.