|Time:||July 8, 2021|
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Prof. Robert Hoy
University of South Florida
Donnerstag, 8. Juli 2021, 16:00 Uhr
“Relating the entanglement of semiflexible polymer melts to their local inter- and intra-chain structure”
Predicting the rheological properties of polymer melts from their microscopic structure has been a longstanding challenge. Several theories developed over the past 50 years accurately predict how quantities such as the plateau modulus G N0 scale with dimensionless parameters such as the ratio of Kuhn length to packing length (l K/p ). However, these theories have limited ranges of validity and are mutually incompatible. We will discuss our efforts to resolve this issue by developing a unified theory for polymer entanglement that reduces to three previous scaling theories (Lin/Noolandi, Edwards/de Gennes, and Morse) in the regimes for which they were designed. Our theory also treats the crossovers between these regimes, and has been made quantitative by obtaining the relevant chemistry-independent prefactors using molecular dynamics simulations and topological analyses. It is consistent with the theory developed simultaneously and independently by Milner and Bobbili; the two theories are complementary in the sense that each explains things that the other does not. Finally, it agrees well with experiment, and is applicable to recently developed conjugated polymers which possess a melt rheology that cannot be explained by either the L/N model or the Morse model.