MSE Colloquium: Karen Winey, Precise Polyethylenes that Control Nanoscale Morphologies & Properties

Professor and Chair, Department of Materials Science and Engineering, Un of Pennsylvania

Abstract

Acid- and ion-containing polymers have specific interactions that produce both acid- or ion-rich aggregates arranged in hierarchical nanoscale morphologies and remarkable bulk properties.  Untangling the correlations between the primary structure of such associating polymers and their morphologies and properties has long been a challenge in polymer physics, because most acid- and ion-containing polymers have random sequences of polar and non-polar monomeric units.  New synthetic methods increasingly produce polymers with greater molecular precision that provide greater uniformity of and control over the hierarchical morphologies and even yield new morphologies.  Specifically, we have studied a series of precise polyethylenes synthesized by acyclic diene metathesis (ADMET) chemistry that have functional groups evenly spaced along linear polyethylenes.  We have established design rules connecting these precise polymers to particular hierarchical morphologies and have discovered a variety of new morphologies.  This talk will focus on how one of these structures exhibits well-controlled chain folding in a precise sulfonated polyethylene to produce a highly uniform morphology with high proton conductivity.  The linear polyethylene contains sulfonic acid groups pendant to precisely every 21st carbon atom, and the acid groups induce tight chain folds upon crystallization of the alkyl segments.  Many consecutive alternating layers of crystalline alkyl segments and hydrated acid groups are formed, with periodicity ~ 2.5 nm.  The proton conductivity through these layers is on par with Nafion 117, the industry standard for fuel cell membranes.  The polymer architecture, namely the placement of the acid groups, is paramount is dictating the morphology and controlling the desired properties.

 

Bio

 

Karen I. Winey is Department Chair, Professor and TowerBrook Foundation Faculty Fellow of Materials Science and Engineering at the University of Pennsylvania with a secondary appointment in Chemical and Biomolecular Engineering.  Karen received her B.S. from Cornell University in materials science and engineering and her Ph.D. in polymer science and engineering from the University of Massachusetts, Amherst.  Following a postdoctoral position at AT&T Bell Laboratories, she joined the faculty of the University of Pennsylvania in 1992.  Karen characterizes and manipulates nanoscale structures in ionomers and associating polymers to develop materials with improved mechanical and transport properties.  Recently, she discovered new structures in several acid- and ion-containing precise polyethylenes.  Karen also designs and fabricates polymer nanocomposites to understand and improve their mechanical, thermal, and electrical properties, particularly transparent conductors.  Polymer motion in the presence of nanoparticles and in nanoconfinement are currently areas of interest.  Across these research areas, Karen couples experimental studies with simulation and theory, either within her group or with collaborators.  Karen has served the research community as Chair of the Division of Polymer Physics within the American Physical Society (2013).  Winey also served as an Associate Editor for Macromolecules (2010-14), the leading journal in the field.  Karen has numerous honors including Fellow of the American Physical Society (2003), George H. Heilmeier Faculty Award for Excellence in Research (2012), Fellow of the Materials Research Society (2013), Visiting Miller Research Professor at the University of California, Berkeley (2014), and Fellow of the PMSE Division within the American Chemical Society (2016).