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The effect of flow on polymer conformation and polymer adsorption
Abstract
The flow-induced birefringence of dilute polymer solutions in periodically constricted tubes and converging-diverging channels has been employed to study the dynamics of polymer chains under transient stretching stresses. Under these conditions, flexible and semi-flexible systems exhibit memories on time scales much greater than normally displayed at equilibrium. The dynamic behavior of polymer chains determines the rheological properties of polymeric solutions. A correlation has been found between molecular deformation and the excess pressure drop effect observed in porous media flows. In the case of flexible chains, the presence of centerline birefringence (which is associated with purely elongational flow) coincides with the sudden increase in pressure drop of the polymeric solution. The influence of flow on the adsorption and desorption of high molecular weight poly(styrene) on chromium has also been studied, by ellipsometry, for two solution conditions: in decalin at 22$\sp\circ$C (a slightly good solvent), and in cyclohexane at 35$\sp\circ$C (a theta solvent). Measurements of layer thickness after collapse induced by solvent removal provide adsorption levels (mass/area) in both shear (0 $<$ $\dot\gamma$ $<$ 1000 s$\sp{-1}$) and biaxial elongation (0 $<$ $\dot\varepsilon$ $<$ 25,000 s$\sp{-1}$). With decalin, the different flow environments have little influence on either adsorption or desorption processes; with cyclohexane, a greater impact is noted, although only in adsorption. It appears that flow only affects the adsorption level of a weakly attached subfraction of the bound chain population.
Subject Area
Chemical engineering|Polymer chemistry
Recommended Citation
Chin, Susana, "The effect of flow on polymer conformation and polymer adsorption" (1991). Doctoral Dissertations Available from Proquest. AAI9120861.
https://scholarworks.umass.edu/dissertations/AAI9120861