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CHBE 565 Seminar, Prof. Marc Hillmyer, University of Minnesota, "Harnessing Disorder in Self-assembled Block Polymers for Functional Nanostructured Materials"

Event Type
Chemical and Biomolecular Engineering and International Paper Co.
116 Roger Adams Laboratory
Apr 9, 2019   2:00 pm  
Christy Bowser
Originating Calendar
Chemical & Biomolecular Engineering Seminars and Events

Self-assembled block polymers containing functional macromolecular components are versatile precursors to useful nanostructured materials. An interesting morphology used to generate nanostructured soft materials in this way is the double gyroid. The gyroid phase has the attractive feature of being bicontinuous and thus nanostructure orientation is not needed to achieve domain continuity while retaining a supporting mechanical phase. These features can be particularly useful for numerous membrane-based applications such as in ultrafiltration, photovoltaics, and polymeric electrolytes. While we have been able to access the bicontinuous double gyroid phase in, for example, polystyrene-block-polylactide copolymers, etching those structures results in nanoporous materials that are not mechanically robust. Moreover, the gyroid structure can only be accessed over a small slice of composition in the diblock copolymer morphology map. Thus, we have worked to access block polymer nanostructures that are bicontinuous and mechanically robust but that do not necessitate the formation of the gyroid or other related ordered morphologies. I will discuss our recent approaches to nanostructured, bicontinuous disordered morphologies through either thermal or light-induced chemical fixation of block polymers in the disordered state in close proximity to the order-disorder transition. This will include our recent work on (i) how we use the in situ and controlled formation of crosslinked block polymers to trap an emerging disordered state and (ii) how we use the thermally accessible order-disorder transition to decouple the formation of a disordered phase and chemical fixation. In both cases, composition fluctuations in disordered block polymers can be trapped. In the examples where one of the blocks is chemically etchable (e.g., polylactide), nanoporous polymers with narrow pore size distributions can be generated and utilized as, for example, ultrafiltration membranes for water purification. I will focus on the preparation, characterization and applications of this interesting class of nanostructured materials.

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