Diffuse versus point entanglements ― homopolymers and blends

Mechanical properties of linear polymers are frequently described via identification of the tangle of chains with an equivalent temporary network. An alternative model is presented assuming diffuse entanglements, in keeping with the tube model. This model allows entanglement molecular weights to be predicted from knowledge of conformational characteristics of the chains. Predictions of the diffuse entanglement model and of the temporary network model are compared with experimental data on critical molecular weight from viscosity and entanglement molecular weight of binary blends (PPO-PS), and on crazing properties. Both models exhibit similar trends, although quantitative description is generally better under the assumption of diffuse entanglements. 39 ref.--AA