报告题目：Auto-Dispersing and Stimuli-Responsive Polyurethane Dispersions
报告人：Prof. John Texter
Eastern Michigan University, Ypsilanti, MI, 48197, USA
Abstract：Free-energy driven dispersion formation is of interest because microscopic to nanoscopic phase separation from macroscopic phases of chemical components involves an intriguing balance of chemical forces that results in apparent thermodynamic stability. We earlier demonstrated how stimuli-responsive block copolymers comprising polymerized ionic liquid (PIL) blocks could be prepared by modified emulsion polymerization approaches, and demonstrated reversible particle precipitation in a nano-scale range. Here we report a single-pot condensation polymerization approach to synthesizing polyurethanes (PUs) in solvent, wherein aqueous compatibility is induced by using imidazolium hydroxide salts (ionic liquids) as chain terminating groups. Effects of various diisocyanates, diols, crosslinking agents, and chain terminators on the creation of PUDs (polyurethane dispersions) are described with respect to impact on spontaneous self-dispersing when such PUs are dried (of solvent) and placed in water. The size evolution of such (self) dispersion is examined by videography and by dynamic light scattering, and size reduction from more strenuous activation by sonication is studied. Effects of indifferent salt on aqueous stability are measured, and anion-dependent stimuli-responsiveness is demonstrated and characterized. This stimuli-responsiveness appears based on tuning imidazolium-anion pair solubility by anion exchange. Film formation is also examined. Water-sensitive films with weak mechanical properties are obtained and appear promising for hydrogel delivery applications.
John Texter is professor of polymers and coating at Eastern Michigan University. He obtained his BSEE from Lehigh University where he also received MS degrees in chemistry and mathematics and a PhD in chemistry. He spent 25 years at Eastman Kodak Company and Strider Research Corporation and a year at the National Science Foundation before initiating his professorship. His research interests include advanced polymer materials, solvent-free nanofluids, and particle dispersion science and technology.