Utilizing Solvent- and Polymerization-Induced Morphology Transitions to Create Nanostructured Materials
Colloidal and bulk block polymer nanostructured materials fabricated via solvent- or polymerization-induced structural transitions have been used in a host of applications ranging from biomedical to energy technologies. In both methods, the resulting nanostructure forms due to a change in the initial environment by either altering the solvent quality or the compatibility between polymers during polymerization. The work presented here discusses two techniques, solvent- and polymerization-induced structural transitions, which our group has recently utilized to create nanostructured materials. The first part of the talk focuses on creating physically crosslinked hydrogels using amphiphilic triblock copolymers that will rapidly self-assemble when injected into water. We have developed a universal and quantitative method for fabricating and controlling physically crosslinked hydrogels exhibiting hierarchical ordering and structural color using a solvent-non-solvent rapid-injection process. The second part of the presentation describes how in situ polymer grafting drives interesting and controllable morphology transitions. In our approach, we are able to induce a lamellar-to-hexagonally-packed cylinder transition via the polymerization of styrene, which initially acts as a neutral solvent for the lamellar-forming diblock copolymer, poly(styrene)-block-poly(butadiene). Furthermore, in situ small-angle X-ray scattering (SAXS) experiments during the polymerization process reveal a complex phase path in which the hexagonally-perforated lamellae is an intermediate morphology between the lamellar and hexagonally-packed cylinder phases. The work presented here highlights how polymer chain architecture, and kinetic and chemical processes can be utilized to create nanostructured materials.