Discovery of Self-Assembled Network Phases And Metallic Nanostructures Driven by Confinement

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

NON-TECHNICAL SUMMARY: Block copolymers are a class of polymers that contain two or more chemically distinct units. As a result, these polymers can spontaneously arrange themselves to produce dense arrays of nanoscale periodic structures with spacings of ~10–100 nm. These materials are useful in a range of nanoscale technologies, including the manufacture of integrated circuits and porous membranes for filtration or separation. This proposal explores a type of block copolymer called a Janus multiblock bottlebrush copolymer, in which the molecules consist of a backbone to which sidechains of three or more different polymer compositions are attached. These materials self-assemble into nanoscale structures with unusual morphologies such as layers of mesh-like structures, which cannot be formed from common block copolymers, making the Janus polymers interesting for nanomanufacturing. The proposal has two major aims: first, testing hypotheses about the formation of novel morphologies, and second, introducing a metal-containing group into the polymer to enable the formation of useful nanostructures such as microelectronic metallization wires. Success in reaching these goals will contribute to solving longstanding needs in nanofabrication based on self-assembly; in particular, the fabrication of metallic meshes and rectilinear nanostructures. Broader impacts include training of students, public events, and outreach activities to promote diversity in science and engineering. TECHNICAL SUMMARY: This proposal explores a class of Janus multiblock bottlebrush copolymers that microphase- separate to form structures with hierarchical length scales consisting of a substructure within a superstructure such as mesh-in-lamella. The morphologies of Janus bottlebrush multiblock copolymers differ qualitatively from those of Janus bottlebrush diblock copolymers and the role of the confinement of the molecules within the superstructure on the substructure assembly will be investigated both experimentally and computationally. Furthermore, the proposal develops methods to incorporate a block consisting of metal-containing N-heterocyclic carbenes (NHC) via a poly(NHC metallopolymer) branched macromonomer route, facilitating the selective introduction of metal species within the block copolymer. Thin film morphologies and directed self-assembly of Janus bottlebrush multiblock copolymers will be investigated using solvent annealing combined with structural analysis, and metal nanostructures such as meshes will be fabricated. The proposed research will broaden the range of self-assembled morphologies obtainable from block copolymer self-assembly, as well as extending the utility of bottlebrush copolymers by introducing a metal-containing block. Morphologies relevant to semiconductor device fabrication will form a particular focus of this project. A graduate student and undergraduates including summer researchers from a local community college will be trained in an interdisciplinary field with the opportunity to interact with a computational collaborator. The results will be incorporated into classroom teaching and seminars and will be organized and archived for public access. The senior researchers and students will engage in public outreach and promotion of diversity through various programs. . 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.