Events

Copolymerization is the incorporation of more than one type of repeat unit into a single polymer backbone. Many plastics used by society are copolymers, whose properties are determined by composition and sequence of different repeat units. We understand the sequencing through experimentally determined reactivity ratios defined by ratios of the propagation rate constants. The copolymer-equation has formed the basis for interpreting copolymerization statistics and reactivity since it was introduced in 1944 by Mayo, Lewis and Wall. While advances in our ability to measure copolymer composition have advanced substantially over the subsequent decades, the underlying conceptual model and methods of using it have changed little. In this talk, I will answer three questions. 1. Of all the methods of determining reactivity ratios, how does one select the right model? 2. How can we use this new understanding to characterize new materials and determine the structure of complex copolymers such as degradable poly(orthoester-co-ether)s or graft architectures derived from monomers with very different steric demand? 3. How do we move beyond the copolymer-equation to understand copolymerizations that cannot even be practically represented mathematically? An important example is degradable poly(lactide-co-glycolide) (PLGA) that is produced using a reversible copolymerization subject to simultaneous transesterification. PLGA is a degradable/sustainable material and an important component in many pharmaceutical applications. To understand PLGA structure and polymers like it, we have developed new methods of extracting reaction parameters from experimental data based on numerical and probabilistic stochastic kinetic models.

Nathaniel A. Lynd is originally from Michigan and educated in the public-school system in the state. Nate started undergraduate research in polymer chemistry after a semester of organic chemistry with the late Gregory L. Baker at Michigan State University. Nate has been a polymer chemist ever since. Drawn to the subject of renewable-resource-derived polymers, Nate moved to the University of Minnesota for his graduate education under Marc A. Hillmyer where he studied the effects of molecular weight distribution on block polymer self-assembly. In late 2007, Nate moved to the west coast for postdoctoral studies at the University of California-Santa Barbara under Glenn H. Fredrickson, Craig J. Hawker, and the late Edward J. Kramer. Eventually, Nate took a position as staff scientist at Lawrence Berkeley National Laboratory in the Materials Sciences Division before joining the faculty in the McKetta Department of Chemical Engineering at The University of Texas at Austin in late 2015. Nate is currently an associate professor and the Laurence E. McMakin, Jr., Centennial Fellow in Chemical Engineering.

*Refreshments will be provided plus a chance to talk with the speaker after their seminar till 5pm.