Understanding the role of conserved dynamic covalent junctions on block copolymer and network self-assembly

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Block copolymers are used in many applications such as epoxies, battery electrolytes, and elastic clothing, and are valued for their ability to combine two functions into one material. This ability comes from bonding two or more polymer chains made of different chemical units called monomers. The differing chemical monomers causes the different blocks of the polymer to separate, like oil and water. However, because they are bonded together, the result is small domains, consisting of one block or the other. Forming a regular, ordered pattern of these small domains is challenging as the ordered phases often exhibit defects, or deviations from the pattern, where the polymer chains become trapped. The investigators propose to introduce dynamic links between blocks that will allow some of the block copolymers to exchange their sections with a nearby block copolymer. The investigators hypothesize that this additional freedom will give the system as a whole greater flexibility to achieve long-range order of the different phases. This faster assembly is expected to reduce processing time, energy, and waste. The investigators plan to incorporate lessons about dynamic polymer characterization and molecular simulation into day-camp projects by partnering with the Girls Learning About Materials and the CURIE Camp@Illinois organizations.This proposal aims to understand the effects of dynamic junctions in block copolymer self-assembly. Including a fraction of exchangeable bonds is expected to increase chain mobility, improve long-range order and reduce time, energy and waste during the annealing process. To test this hypothesis, the investigators will synthesize block copolymer systems that include both permanent and dynamic junctions. Both polystyrene and polyisoprene block copolymers (PS-PI) and polyethylene oxide and polydimethylsiloxane (PEO-PDMS) will be studied at various molecular weights, using small angle x-ray scattering (SAXS) to assess the morphology. The investigators will also model this system using self-consistent field theory. The investigators will also explore the role of additional chains at a dynamic junction, by modeling and characterizing dynamic miktoarm star polymers and contrasting with dynamic diblock copolymers, again using both experimental and computational approaches. The expected outcome of this project are fundamental insights into the role of dynamic on block copolymer self-assembly and mechanisms to reduce kinetically trapped defects.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.