Role of polydispersity in the rheology of a branched polymer

点击翻译按钮获取中文摘要

Since the advent of models for entangled polymers based on the concept of a "molecule in a tube", pioneered by Doi and Edwards, there has been a steady advance in our ability to make quantitative predictions of the rheological behavior of molten polymers of known molecular structure. Originally developed for linear, monodisperse polymers, the Doi-Edward theory has been elaborated to deal with polydisperse linear polymers and monodisperse, branched systems. There has also been some progress in the modeling of branched systems with a limited degree of polydispersity. A final barrier to the use of these mean-field molecular theories to describe polymers of industrial importance is the lack of a reliable model for broadly polydisperse branched polymers having at least two branch points per molecule. Prof. R. G. Larson of the University of Michigan has developed a hierarchical approach to this problem, and it is now proposed to incorporate this model into an algorithm capable of predicting the rheological behavior of branched polymer having polydispersity in the lengths of the branches. The predictions will be compared with data for samples having branching structures and polydispersities that are precisely known. Next, an accurate rheological characterization of the samples will be carried out, the data will be compared with the predictions of the model, and any deficiencies that become apparent will be addressed. The successful completion of the project will provide information of interest to polymer scientists as well as companies wishing to develop new polymer structures for specific applications. It will also be of interest to examine how the model might be used to infer molecular structure from rheological data.