[ChBE-Grad] UH ChBE SABIC Seminar this Friday, February 24

[Solano, Nicolette]

[William A. Brookshire Department of Chemical and Biomolecular Engineering Seminar Series]<https://www.chee.uh.edu>


Loop-in Complexation of Non-Stoichiometric Polyelectrolyte Solutions


Jian Qin
Assistant Professor
Stanford University

Friday, February 24 | 10:30am Central
Engineering, room W122



LECTURE ABSTRACT
Polyelectrolyte complexation resuls from a well-known demixing instability, which originates from sufficiently strong electrostatic correlation. The instability is difficult to model quantitatively because of its sensitivity to a variety of short-ranged features including monomeric polarity, molecular flexibility, and charge pattern. The recent theoretical advancements have enabled a consistent treatment of short-ranged interactions and long-ranged electrostatic correlations, potentially allowing for an improved description of complexation phenomena. To put the theory into test, we designed calibrated experiments using polycation and polyanion with identical backbones, and with viariable polarity and mixing stoichiometry. Aided with dual-fluorescent labeling and elemental mapping, we determined the binodal diagrams, and revealed a hitherto unexpected reentrant behavior in highly non-stoichiometric solutions, which compares favorably to theoretical predictions. The reentrant behavior, i.e., salting out in response to salt addition, is shown to be caused by the entropy of charge-neutralizing counter ions, a scenario reminiscent of the Donnan equilibrium.



SPEAKER BIOSKETCH
Jian Qin is an Assistant Professor in the Department of Chemical Engineering at Stanford University. He received B.S. and M.S. degrees in Materials Science from Tsinghua University, and his Ph.D. from University of Minnesota under the supervision of Profs. David Morse and Frank Bates. Following postdoctoral fellowships at Pennsylvania State University, with Prof. Scott Milner, and The University of Chicago, with Prof. Juan de Pablo, he joined Stanford University as a Terman Faculty Fellow in 2016. His research focuses on theoretical study of morphological and rheological behavior of polymeric fluids, electrostatic interactions in structured electrolytes, and surface charge polarization. He has held the Kadanoff-Rice Fellowship and has been recognized by the 3M Non-Tenured Faculty Award, the Hellman Faculty Award, the NSF CAREER Award, the ACS PMSE Arthur Doolittle Award, the ACS PMSE Young Investigator Award, the Tau Beta Pi (Stanford) Teaching Honor Roll, and the APS Dillon Medal.





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