title: Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents.
abstract: Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymerde novowithin the corresponding volume ratio of the blocks. In this work, we investigated solvent vapor annealing in supported thin films of poly(2-hydroxyethyl methacrylate)-block-poly(methyl methacrylate) [PHEMA-b-PMMA] by means of grazing incidence small angle X-ray scattering (GISAXS). A spin-coated thin film of lamellar block copolymer was solvent vapor annealed to induce microphase separation and improve the long-range order of the self-assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents (methanol, MeOH, and tetrahydrofuran, THF), which are chosen to be preferential for each block, enabled selective formation of ordered lamellae, gyroid, hexagonal or spherical morphologies from a single block copolymer with a fixed volume fraction. The selected microstructure was then kinetically trapped in the dry film by rapid drying. To our knowledge, this paper describes the first reported case wherein-situmethods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram.
authors.affiliation: Department Of Materials Science and Engineering 214 Bard Hall, Cornell University, Ithaca, NY 14853 USA mac238@cornell.edu.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Chavis
authors.affiliation: Cornell High Energy Synchrotron Source 161 Synchrotron Drive, Cornell University, Ithaca, NY 14853 USA.
authors.forename: Detlef-M
authors.initials: DM
authors.lastname: Smilgies
authors.affiliation: Department Of Materials Science and Engineering 214 Bard Hall, Cornell University, Ithaca, NY 14853 USA.
authors.forename: Ulrich B
authors.initials: UB
authors.lastname: Wiesner
authors.affiliation: Department Of Materials Science and Engineering 214 Bard Hall, Cornell University, Ithaca, NY 14853 USA.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Ober
keywords: block copolymers; microphase separation; self-assembled; solvent vapor annealing; tunable morphologies
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