The Department of Chemical and Biological Engineering is pleased to welcome Zhen-Gang Wang from the California Institute of Technology for a seminar titled:
Self-Assembly of End-Charged Block Copolymers and Blends: Effects of Ion Clustering
ABSTRACT: Adding ionic groups to polymer chain ends—whether within a single diblock copolymer or across two different homopolymers in a blend—offers a promising route to direct self-assembly for applications ranging from compatibilizing immiscible polymer blends to templating functional and ion-conducting nanostructures. Using self-consistent field theory that accounts for strong ion correlations, we show that under low-dielectric conditions typical for polymers, charged ends aggregate into multi-ion clusters that fundamentally alter assembly behavior. In end-charged diblock copolymers, these clusters act as compact, curvature-favoring foci, enabling complex network phases such as single primitive and single gyroid—structures that are absent in neutral diblocks. In binary blends with oppositely charged ends, electrostatic attraction suppresses macroscopic phase separation and induces microphase separation. However, the resulting phase diagram is simpler (dominated by lamellar and cylindrical phases) than the effective diblock picture would predict. This difference arises because ion clusters reside at the interface in blends, where they resist curvature, unlike in diblocks where they organize the surrounding chains. Notably, both systems form ordered microstructures at significantly lower segregation strengths than the corresponding uncharged diblock copolymers.
Zhen-Gang Wang received his B.Sc. in Chemistry in 1982 from Beijing (Peking) University, and his Ph.D. in Chemistry in 1987 from the University of Chicago. He did postdoctoral research first in Exxon Research and Engineering Company and then at UCLA. Since 1991 he has been on the Chemical Engineering faculty at the California Institute of Technology, where he is currently the Dick and Barbara Dickinson Professor. He has also served as Executive Officer (department chair) for Chemical Engineering for 6 years.
Wang’s research is the theoretical and computational study of structure, phase behavior, interfacial properties and dynamics of polymers, soft materials, and biophysical systems. His current activities revolve around three main themes: charged systems, including polyelectrolytes, salt-doped polymers, and electric double layers; nucleation or more generally barrier crossing in polymers and soft matter; and nonlinear rheology of polymer gels and entangled polymers.
Wang is a fellow of the American Physical Society and a member of the U. S. National Academy of Engineering. He is recipient of several significant awards and honors, including the Camille Dreyfus Teacher–Scholar Award (1995), the Alfred P. Sloan Award (1996), the Braskem Award from the American Institute of Chemical Engineers (AIChE) (2018), the AIChE Alpha Chi Sigma Award (2023), and the American Physical Society Polymer Physics Prize (2024). In addition, he was awarded the Richard P. Feynman Prize for Excellence in Teaching (2008), Caltech’s highest teaching honor.
Wang has served on the editorial advisory boards of Journal of Theoretical and Computational Chemistry, Macromolecules, ACS Macro Letters, Giant, Acta Physicochimica Sinica, and Science in China B (Chemistry). He is currently an associate editor for the ACS Journal Macromolecules.
Dr. Wang's seminar will be hosted by Northwestern faculty, Krishna Shrinivas.
Cost: Free
Olivia Wise
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