Understanding Structure and Response in Thermally-Responsive Block Copolymer Assemblies

TECHNICAL SUMMARY: Responsive polymer assemblies show great promise in a range of applications, including drug delivery, sensing, and catalysis. Crucial to the elaboration of these systems is the development of polymers that undergo rapid, predictable, and reversible changes between assemblies with different sizes and structures. For applications involving encapsulation of other species within polymer vesicles, the development of more efficient encapsulation methods is also of great importance. To meet these challenges, the PI and co-workers have previously prepared temperature-responsive ABC triblock copolymers with poly(ethylene oxide) (PEO) as a hydrophilic block, poly(N-isopropylacrylamide) as a thermoresponsive block, and polyisprene as a cross-linkable hydrophobic block, which form assemblies that undergo large changes in size and shape around a critical temperature, however the reorganization of small assemblies (micelles of 20 nm diameter) into larger assemblies (vesicles of >100 nm diameter) at elevated temperatures was found to take several weeks. Recently, related copolymers with poly(butylene oxide-stat-ethylene oxide) responsive blocks, in which there are weaker interchain interactions in the absence of water, were found to undergo significant structural transformations within several hours. This research will probe the hypothesis that weakening interchain interactions in the dehydrated state is critical to increasing assembly transformation rate. This research will further the understanding of these block copolymer systems and their potential applications. Specifically, the PI and co-workers will investigate new hydrophilic-responsive-hydrophobic triblock copolymers, further probe possible structural transformations (e.g., micelle-to-worm-like micelle), more deeply investigate the kinetics of the assembly transformation process, and carry out encapsulation and release studies with block copolymer assemblies. The further study of these novel responsive systems offers the potential to expand and transform the applications of polymer-based nanostructures. NON-TECHNICAL SUMMARY: Nanometer-sized assemblies of polymer molecules show much promise in a range of applications, from the treatment of cancer and other diseases to the development of new sensory devices. This research will further our understanding of polymer assemblies that are designed to undergo specific changes in size and shape upon exposure to heat or other stimuli. In doing so, it will lay the groundwork for future efforts to use these materials in applications where the response to stimulus can be coupled to a specific application, such as release of a chemotherapy agent or the detection of specific molecules. This research will be carried out by graduate and undergraduate students as part of their scientific training and will involve collaboration with other researchers at Stony Brook University, Brookhaven National Laboratory, and Warwick University (UK). The PI will work through the State University of New York Louis Stokes Alliance for Minority Participation (SUNY LSAMP) program to recruit undergraduate students to participate in research in the chemistry department. Results of this work will be presented at internationally-attended scientific meetings and the PhD students involved in the project will maintain a website/blog through which they will be able to communicate their reflections on the project and the life of a scientific researcher to the general public.