TESTING AND MEASURING Molecular-Scale Polymer Melts Response to shear in the linear and non-linear rheological Domains: Affect of molecular Weight and complex Architecture

The molecular-level response to shear of entangled polymers at interfaces and in the bulk has been of interest to un derstand the non-linear rheological res ponse of polymers. Here we focus on the molecular level response to shear strain leading non-linear rheological phenomenon, in linear and star poly mers comparing the observed response to the predictions of tube theory. We used SANS measurements of the bulk polymer response to shear in Couette geometry on melts of high molecular weight mixtures of polymers extending our previous results on interfacial res ponses with rheoNR measurements in cone-and-plate geometry. 

The problem of understanding the relati onship between the bulk rheological pro perties of entangled polymeric liquids and the polymer molecular architecture is one of the most interesting and impor tant problems of polymer science. Polymers, as non-Newtonian fluids, exhi bit a number of critical rheological pro perties from a practical and industrial perspective, as under high strain ra tes, γ (Hz), polymers show non-linear viscoelastic properties, the structural fundamentals of which are not well un derstood. Furthermore, there is interest in mixtures of linear polymers with those having complex architectures, such as stars, for producing blends with optimal properties