Elucidating Grain Boundary Complexion Transitions and their Role on Grain Growth in Granular Block Copolymer Microstructures

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

NON-TECHNICAL SUMMARY Block copolymers are materials that are capable of self-organizing into functional nanostructures that are of technological relevance in applications ranging from membranes for water purification to next-generation lithium ion batteries to high-performance polymer photovoltaics. The realization of these technologies is hindered by defects in block copolymer nanostructures that form during the self-organization process and that reduce the properties of materials. The goal of this project is to establish a transformative new process to control and reduce the number of defects in block copolymer nanostructures. This will promote the development of scalable and economic fabrication processes for materials with improved properties. The program will support the teaching of a new laboratory course on polymer materials and provide training for one graduate student and several undergraduate student researchers. Ongoing collaborations with educators at minority serving institutions will be leveraged to support the participation of minority students. Finally, the potential of novel educational technologies based on 'haptic human-computer interactions' as a means to engage and attract middle and high school students to the study of science and engineering will be established. TECHNICAL SUMMARY The fabrication of large-grained microstructures with reduced defect densities presents a prerequisite to the application of block copolymer (BCP) materials across a wide range of innovative material technologies. Understanding of the mechanism of grain growth and the evolution of defect structures during the annealing process is therefore a subject that is of fundamental relevance to both the science and engineering of BCP-based materials. The objective of this project is to elucidate the role of filler-matrix interactions on grain coarsening in miscible BCP/homopolymer blends and to test the hypothesis that grain boundary complexion transitions -- i.e. transitions within the phase of filler that is segregated to grain boundary interfaces -- increase the driving pressure for grain growth and hence the rate of grain coarsening. In a first part, the program will be focused on establishing the miscibility range and (equilibrium) microdomain formation in BCP/homopolymer blends systems in which the homopolymer forms a LCST blend with the host copolymer domain. In a second part, the project will focus on establishing the effect of filler/matrix interactions on the energy of grain boundary interfaces in quiescent organized films. If successful, this project will provide a basis for the development of novel processing strategies towards low defect-density BCP materials that harness the 'catalytic' effect of designed filler additives on grain coarsening to efficiently organize BCPs into desired large-grained microstructures. The program will enhance the teaching of a new class on "Soft Material Microstructure and Properties" and provide training for one graduate and several undergraduate researchers in the critical area of polymer and nanoscale materials. Finally, the benefits of kinesthetic experiments to the teaching of polymer and material science will be evaluated.