Linear viscoelasticity of branched polymer melts.

TL;DRAbstract

Standard analytical techniques like chromatography and spectrometry are not sensitive enough to resolve architectural details in branched polymer melts such as metallocene-catalyzed polyethylene to industrially acceptable levels. This has led to the belief that linear rheology, which is highly responsive to subtle differences in branching structure, can be employed as an analytical technique. A major difficulty hindering the application of rheology as an analytical tool has been the inability of the current analytical theory for branched polymers, which is based on the idea of dynamic dilution, to describe the physics of branch point motion. We examine shortcomings of this theory, including the problem of branch point motion, using three case studies. We use a simulation model called the dual slip link model in which entanglements between chains are modeled as slip links that couple the dynamics of pairs of chains. First, in the late-time relaxation of symmetric stars we investigate th

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