CBE Seminar - Karen Winey

Precise Acid- and Ion-Containing Copolymers: New Morphologies and New Insights about Mechanical Properties

All dates for this event occur in the past.

130 CBEC
130 CBEC
151 W. Woodruff Ave
Columbus, OH 43210
United States

Karen Winey

Professor and TowerBrook Foundation Faculty

Materials Science and Engineering and Chemical and Biomolecular Engineering

University of Pennsylvania

Precise Acid- and Ion-Containing Copolymers: New Morphologies and New Insights about Mechanical Properties

Abstract

Acid- and ion-containing polymers have specific interactions that produce complex and hierarchical morphologies that impart remarkable ranges of tunable properties.  Renewed interest in these materials arises from various applications including as single-ion conductors in battery applications, selective membranes for water treatment, and self-healing materials.  Most of these polymers are copolymers and often random copolymers wherein the separation between the functional groups on the polymers is non-uniform and individual copolymers have distinct compositions.  This inherent structural diversity confounds the longstanding efforts to establish robust structure-property relationships.  In contrast, precise acid copolymers and their ionomers are synthesized by acyclic diene metathesis (ADMET) from macromonomers, such that the functional groups are evenly spaced along linear polyethylene.  These unique model materials provide molecular precision that imparts unprecedented morphological uniformity and control and we have identified numerous new morphologies.  Our primary experimental tool is X-ray scattering to probe the nano-scale morphology a room temperature, elevated temperature and during mechanical deformation.  At elevated temperatures, we find outstanding agreement with course grain and atomistic molecular dynamics simulations that provide new insights about acid and ionic aggregation in these materials.  In particular, the experiments and simulations suggest the presence of highly branched, stringy aggregates that can be percolated structures at high acid or ion content.  The relationships between the chemical structures of precise copolymers, their hierarchical aggregate structures and the effect on mechanical properties have been explored using in situ tensile testing with X-ray scattering.  When the acid groups are separated by 15 carbons, the precise copolymer exhibits a structural transformation from a nominally spherical to a layered aggregate morphology during tensile deformation that coincides with substantial strain hardening. This structural transformation is particularly sensitive to the strain rate, because the relaxation times of the polyethylene segments and the acid aggregates are accessible. Commensurate with this structural transformation, this particular polymer has the highest tensile strength of the precise poly(ethylene-co-acrylic acid) copolymers.

Bio
Karen I. Winey is 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.  During her recent sabbatical leave she was a Visiting Miller Research Professor at the University of California, Berkeley and a Visiting Scholar at the Materials Research Laboratory at the University of California, Santa Barbara.

Winey’s current interests include both ion-containing polymers and polymer nanocomposites.  In ion-containing polymers, including block copolymers and polymers with ionic liquids, Winey combines imaging and scattering methods to provide unprecedented insights into their morphologies.  Current efforts focus on correlating nanoscale structures with ion transport and mechanical properties.  In nanocomposites, she has designed and fabricated polymer nanocomposites containing carbon nanotubes and metal nanowires with the aim of understanding how to improve their mechanical, thermal, and especially electrical conductivity and resistive switching properties.  Polymer dynamics in the presence of nanoparticles and other types of nanoconfinement is an active area of interest.  In both areas, she couples experimental studies with simulation and theory, either within her group or with collaborators. Winey holds 12 patents and has published over 175 papers (h-index 51).

Winey 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 with Ned Thomas as her thesis advisor.  Following a postdoctoral position at AT&T Bell Laboratories with Ron Larson, she joined the faculty of the University of Pennsylvania in 1992.  Elected positions include chair of the Polymer Physics Gordon Research Conference (2010) and Chair of the Division of Polymer Physics within the American Physical Society (2013).  Winey also served as an Associate Editor for Macromolecules, the premier journal for polymer science, for four years (2010-14). Her honors include Fellow of the American Physical Society (2003), a Special Creativity Award from the National Science Foundation (2009-2011), the George H. Heilmeier Faculty Award for Excellence in Research (2012), and Fellow of the Materials Research Society (2013).

 

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