Viscoelasticity of low molecular weight polymers and the transition to the entangled regime

摘要: The viscoelasticity of unentangled polystyrene melts has been investigated in terms terminals parameters: zero-shear viscosity, steady-state compliance and relaxation spectrum. Rouse model applies well for molecular weights lower than the average weight between entanglements, providing that one takes into account proper variations radius gyration. Moreover, local motions at scale Kuhn segments have to be considered order describe correctly modes intermediate terminal zone glassy plateau. On other hand, reptation models are commonly used describing entangled regime. We propose an expression shear modulus which accounts not only (reptation, tube length fluctuations renewal), but also responsible plateau transition A crossover region untangled regimes is located around . When increases, a shift transfer towards occurs. That leads continuity over entire range weights.