Microviscoelasticity and Viscoelastic Properties of Linear Flexible-Chain Polymers
A concept of microviscoelasticity is introduced, according to which the motion of a macromolecule among similar ones is assumed to be equivalent to its motion in a viscoelastic medium whose characteristics are not known in advance. Theoretical equations have been derived, expressing the relationship between the components of the complex modulus of a linear viscoelastic liquid with an arbitrary set of relaxation times and a low-concentration polymer solution in it.
With a view to establishing a quantitative relation between the micro-and observed macroviscoelasticity, binary mixtures of 1,4-polybutadienes with a narrow molecular-weight distribution have been investigated, their molecular weights being 10 to 100 times different. The content of the high-molecular component varied from 0.1 to 10%.
These polymer mixtures have been experimentally found to exhibit different viscoelastic behaviors in different regions of concentrations of the high-molecular component, and a narrow region of composition with a corresponding “critical” concentration has been established. The calculations of the critical concentration values corresponding to the beginning of polymer coil overlapping, agree well with the experiment.