Use Particle-Tracking Velocimetric Observations to Guide Evidence-Based Investigations of PolymerDynamics in Presence of Chain Entanglement

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TECHNICAL SUMMARYThe proposed research aims to achieve three objectives: (A) carefully examining the previous results to identify potential sources of technical error and scientific ambiguity; (B) removing experimental difficulties to verify whether the new emerging picture would still hold in absence of any artifacts that have caused controversies in the literature; (C) building on the newly available understanding to further probe the nature of disintegration of chain entanglement network due to external deformation. Specifically, many current findings have not been proved to beyond doubt and cannot form the new phenomenological foundation for polymer rheology unless improved experiments are carried out. These experiments include (i) interrogation of strain-induced chain disentanglement under circumstances where the sample at the edge of a shear cell would not suffer fracture and (ii) flow birefringence measurements in absence of any inclusions such as solid particles that have been suspected by de Gennes to be the source of shear banding. Single-molecule imaging velocimetry is proposed as an effective method to probe velocity field in entangled systems without any foreign particles and to directly determine whether shear inhomogeneity would arise from flow-induced polymer migration or from non-uniform chain disentanglement. Finally, in anticipation of potential implications for polymer processing, particle-tracking velocimetric technique will be applied to examine effect of chain disentanglement in pressure-driven flow and related phenomena.NON-TECHNICAL SUMMARY:Each year, more than two hundred billion pounds of plastic and rubber materials are made into consumer products in this country. Such a huge volume typically flows in a manner similar to pouring honey or squeezing tooth paste. How the various polymeric materials flow under different processing conditions is a subject of both academic and economic importance. The fruits of the proposed studies could alter our long-held knowledge about polymer flow and transform the contents of existing textbooks on the subject. Current scientific findings and proposed research offer new hope that could eventually give the domestic market a cutting edge in the global competition and innovation for more efficient production of petroleum-based consumer goods of higher quality. Ultimately, the outcome of the proposed work could directly impact the R&D directions in the plastic and rubber industries. The impact of this investigation is clearly going beyond the border of the United State, as the emerging new picture begins to be discussed in classroom and recorded for video streaming on the world wide web at http://eres.avs.uakron.edu/eres/coursepass.aspx?cid=647. The visualization-intensive nature of the research also makes it attractive materials for youngsters in middle and high schools, making science intuitive, observational and straightforward to perceive.