Doubly Thermosensitive Block and Star Copolymers from Living Radical Polymerizations: Synthesis, Phase Transitions, and Applications

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

TECHNICAL SUMMARY: This project seeks to develop well-defined thermosensitive block and star copolymers that exhibit double thermo-induced phase transitions in water, to achieve fundamental understanding of the effects of molecular weight and molecular structure on the phase behavior, and to elucidate the structures of temperature-induced self-assemblies in water. Specifically, a variety of linear and star block copolymers with controlled molecular weights, narrow molecular weight distributions, and well-defined architectures will be synthesized by living radical polymerization techniques. The functional monomers recently developed in the PIs laboratory will be used to construct these copolymers along with monomers whose corresponding homopolymers have been reported to exhibit thermoresponsive properties. The phase transitions of these polymers in water will be investigated by turbidimetry, variable temperature 1H NMR spectroscopy, fluorescence spectroscopy, dynamic and static light scattering, differential scanning calorimetry, and rheology measurement. Whether and how the molecular weight and molecular structure affect the responsive properties of block copolymers will be systematically studied. The nanostructures formed from self-assembly of these copolymers in water will be elucidated by transmission electron microscopy. The knowledge gained from this research will provide a guideline for designing thermosensitive water-soluble polymers with multiple transitions. The applications of doubly thermosensitive copolymers in catalysis and triggered release of substances will be pursued. NON-TECHNICAL SUMMARY: With the rapid advance of nanotechnology and biotechnology, intelligent materials that can respond to external stimuli are much needed. The double-thermosensitive water-soluble polymers from this research have potential for practical applications in drug delivery, chemical sensors, catalysis, and bio-nanotechnology. Moreover, this research project provides an excellent setting for training of students in polymer synthesis, characterization, design and fabrication of stimuli-responsive materials. Students at all levels will be integrated into the PIs research and education activities. The PI will also work with local high school teachers through summer programs in his laboratory to develop hands-on experiments for high school chemistry classes.