Nanostructured Polymers and Solvents: Opportunities in Health, Environment, and Energy Applications
Professor Paschalis Alexandridis
Department of Chemistry
University of Washington
Abstract: Synthetic polymers offer prime examples of materials where the molecular organization in the nano- and meso-scale impacts profoundly the material properties and function. Such structuring is central to established products (e.g., fibers, elastomers, coatings) and enables novel applications ranging from drug delivery carriers and implants, to membranes for separations, to solid electrolytes for batteries. Sophisticated inter- and intra-molecular organization is also essential to the function of biological polymers such as proteins, DNA, and polysaccharides.
Copolymers, consisting of covalently-linked blocks of different chemical nature or conformation, present model systems for the elucidation of the connections between polymer chemistry, physics, and engineering. In the "dry" state, block copolymers can attain intramolecular organization via crystallization or hydrogen bonding, and supramolecular organization via segregation of the different blocks. The addition of selective solvents may disrupt certain types of organization but can promote others. For example, copolymers of fixed block composition can self-assemble in the presence of selective solvents to form a variety of thermodynamically stable structures that include ordered arrays of nm-scale spherical, cylindrical or planar assemblies. The solvents provide valuable degrees of freedom for controlling the morphology and, hence, structure/property relationships, and can dramatically affect the local mobility. The utilization as solvents of ionic liquids that exhibit internal structure, negligible vapor pressure, high thermal stability, ionic conductivity, and wide electrochemical stability window can expand significantly the range of polymer applications.
The presentation will utilize findings from our research and the published literature to highlight the interplay between fundamentals of block copolymer self-assembly in selective solvents and their applications in the (a) structuring of waterborne complex fluids with properties tailored for pharmaceutics, (b) environmentally benign synthesis of nanoparticles in a size- and shape-controlled manner, and (c) formulation of ionogels as potential electrolytes for lithium batteries, fuel cells, or dye-sensitized solar cells.