Theory of Viscoelasticity in Temporarity Crosslinked Polymers (IV) Relaxation Spectrum and Molecular Weight Dependence of Viscocity

Abstract

The viscoelastic behavior of concentrated polymer solutions is studied by using the network model composed of the Rouse models which have the viscoelastic interactions with medium in contrast with the case of usual network model. The medium is considered to behave as a viscoelastic medium in the phenomena having long relaxation times in which the effect of entanglement participates in the molecular motion. On the other hand, the medium is regarded as a simple viscous medium in the case of shorter relaxation times, as is done in usual treatment for the Rouse model.
The relaxation spectrum covering the both relaxation time ranges is predicted from the unified rheology equation. It is of the wedge type with a slope −1⁄2 for the shorter relaxation times than the critical value, while for the longer ones of the box type.
The viscosity is proportional to the molecular weight when lower than the critical value, and is proportional to the 3.5th power of molecular weight for sufficiently high molecular weights.