CBE Spring Seminar Series Speaker: Jan Genzer

Description

Tuning the properties of surface-anchored networks in a one-pot reaction

We investigate the properties of surface-anchored polymer networks created via one-pot synthesis using thermally active 6-azidosulfonyl hexyltriethoxy silane (6-ASHTES). 6-ASHTES is a bi-functional gelator that undergoes crosslinking and surface-anchoring reactions when annealed above 100°C. We employ a polyvinylpyrrolidone (PVP) with different molecular weights (10 - 1,300 kDa) as a model system to examine the effect of 6-ASHTES concentration, annealing time, and annealing temperatures on gel formation. A thin film of PVP/6-ASHTES mixture is deposited on a clean silicon wafer and annealed to form network layers. Spectroscopic ellipsometry measures the film thickness of the crosslinked layers from which the gel fraction and swelling ratio are determined. The gel fraction of PVP in the network can be "dialed in" by varying the annealing time, temperature, and concentration of 6-ASHTES in the PVP/6-ASHTES mixture. We describe a simple Monte Carlo simulation model to characterize crosslinking as a function of crosslinker concentration, reaction rate, reaction time, and polymer length. The trends obtained from the model simulations are in qualitative agreement with the experimental data. We will also describe a versatile one-pot synthesis method for creating surface-anchored orthogonal gradient networks using a small bi-functional gelator 4-azidosulfonyl phenethyltrimethoxy silane (4-ASPTMS), which can be activated thermally and by UV light. Finally, we will discuss our efforts to control the adhesion of the elastomer/hydrogel interfaces using sulfonyl azide moieties.
 

Bio: 
Jan Genzer received Dipl.-Ing. in Chemical and Materials Engineering from the University of Chemistry and Technology in Prague, the Czech Republic, in 1989 and a Ph.D. in Materials Science and Engineering from the University of Pennsylvania in 1996. After two post-doctoral stints (Cornell University, 1996-1997, and UCSB, 1997-1998), Genzer joined the chemical engineering faculty at NC State University as an Assistant Professor in the fall of 1998. He is currently the S. Frank and Doris Culberson Distinguished Professor and Associate Department Head in the Chemical and Biomolecular Engineering Department at NC State University. His honors include the Camille Dreyfus Teacher-Scholar Award, NSF CAREER award, John H. Dillon Award of the American Physical Society, NSF Award for Special Creativity, NC State's Outstanding Teacher Award, NC State Alumni Outstanding Research Award, NC State Alumni Distinguished Undergraduate and Graduate Professorships, Alcoa Foundation Distinguished Engineering Award, North Carolina ACS Outstanding Lecturer Award, R.J. Reynolds Tobacco Company Award for Excellence in Teaching, Research, and Extension at NC State University, and the Award from the Society of Polymer Science, Japan. Genzer is a Fellow of the American Physical Society and the Royal Society of Chemistry. The Genzer group is actively involved in research on the behavior of polymers at interfaces and confined geometries, with particular emphasis on assembly, thin films, responsive and shape-memory materials, and materials combinatorial methods.