Multivalent interactions in systems of polyelectrolytes can exhibit dramatic, non-monotonic effects, for example, switching forces from repulsive to attractive, and back to repulsive again, in some cases. The
Tirrell Group has been studying these patterns of behavior with the surface forces apparatus (SFA) and with electrochemical methods, such as cyclic voltammetry, which enables the quantitative determination of the number of multivalent ions residing in thin layers of charged polymers. At fixed ionic strength, all cause strong shrinkage and condensation of poly (styrene sulfonate) brushes over a narrow range ratio of multivalent to monovalent ions. When the multivalent ion is an oppositely charged polymer, new fluid phases can form. The Tirrell Group has clarified the quantitative aspects of the phase diagram for a simplified polyelectrolyte complex system. Charged blocks in copolymers lead to materials with new types of ordered phases. Effects of these multi-valent interactions on supermolecular and biomolecular assembly will be discussed. There are many possibilities for the creation of new materials based on electrostatic assembly involving
Professor Matthew Tirrell has been the founding Pritzker Director and Dean of the Faculty of the Institute for Molecular Engineering at the University of Chicago, and Senior Scientist at the Argonne National Laboratory since 2011. He also served as Deputy Laboratory Director for Science at Argonne from 2015 to 2018. From 2009 to 2011, he was the Arnold and Barbara Silverman Professor and Chair of Bioengineering at the University of California, Berkeley, with additional appointments in Chemical Engineering and Materials Science & Engineering, and as a Faculty Scientist at the Lawrence Berkeley National Laboratory. Professor Tirrell was Dean of Engineering at the University of California, Santa Barbara from 1999 to 2009. From 1977 to 1999, he was on the faculty of Chemical Engineering and Materials Science at the University of Minnesota, where he served as Director of the Biomedical Engineering Institute from 1993 to 1998, and Department Head from 1995 to 1999.
Professor Tirrell is a member of the National Academy of Engineering, the American Academy of Arts & Sciences, and the Indian National Academy of Engineering, and is a Fellow of: the American Institute of Medical and Biological Engineers, the American Association for the Advancement of Science, and the American Physical Society. He has received the Polymer Physics Prize from APS and the Colburn, Professional Progress, Stine, and Walker awards from AIChE. From 2001 to 2010, he was a member of the
Board of Directors of the Santa Barbara Cottage Hospital System and the University of California President’s Board for Administration of the DOE National Laboratories. From 2012 to the present, he has been a Director
and Chair of the Scientific Affairs Committee of the Dreyfus Foundation, dedicated to the support of research in the chemical sciences and engineering. He has recently been a member of C-level technical advisory
boards of Solvay Corporation, S.C. Johnson and Sons, ExxonMobil, SiO2 Medical Products, and Edwards Lifesciences. Tirrell’s technical expertise is in polymer materials, biomaterials, surfaces urfaces and interfaces, and instrumental methods of characterization.