The role of short chain molecules for the rheology of polystyrene melts.

Abstract

Abstract." The influence of short chain molecules (with M < M c ) on the rheology of the melts of binary blends of long and short chain polymers was studied. For this purpose, the complex moduli as functions of circular frequency were examined for these melts and also for melts of unblended long chain samples. For pertinent blending a set of standard polystyrenes with narrow molar mass distribution was used.The short chain component causes a typical diluent effect. This is clearly revealed from the lowering of the plateau modulus of the long chain component. This lowering is found to be proportional to the square of the weight fraction w2 of the long chain component, as theoretically predicted. The reduction of the relaxation times of the long chain molecules turns out to be proportional to w~ '8, when the influence of an increased contribution of chain ends to the free volume is separately taken into account according to the results of the first paper of this series. As the power of w2 in the latter relation is not critical, one can formulate equations for the first normal-stress coefficient and for the zero-shear viscosity as functions of w2M~.~, which merge into the respective M 6'8-and M34-1aws well-established for undiluted high polymers (w2 = 1).

Chain Stiffness of Copolycarbonates Containing a Spiro Linkage

“…This dilution leads to apparently higher M e 's. It was shown by Schausberger et al that scales with the square of the volume fraction of chains with M ≥ M c .…”

Insights into the role of protein molecule size and structure on interfacial properties using designed sequences

“…For example, Kornfield et al [40] observed that short chains relax first followed by long chains in a polymer bimodal melt. Separate work by Shausberger et al [41] found that addition of the short-chain polymer to a long-chain polymer in a binary blend had the effect of lowering the plateau modulus and relaxation time of the long-chain molecule alone. As observed in previous work [38], these results further show parallels between polymer bulk mechanical behaviour and protein interfacial mechanical behaviour, and indicate the field of protein interfacial rheology could benefit from application of theoretical frameworks existing in the mature field of polymer rheology.…”

Recent progress in flow‐induced polymer crystallization

“…68 Subsequently, the discovery of shish-kebab structure and the development of advanced detection technology have triggered the upsurge in FIC research. 61,65,66,[69][70][71][72][73][74][75] Janeschitz-Kriegl et al [76][77][78][79][80] have made the most important connections between FIC and rheology. Janeschitz-Kriegl proposed the concept of specific work as a key parameter on controlling nucleation, which is the product of the external stress and the rate of deformation.…”