title: Continuous equilibrated growth of ordered block copolymer thin films by electrospray deposition.
abstract: Deposition of block copolymer thin films is most often accomplished in a serial process where material is spin coated onto a substrate and subsequently annealed, either thermally or by solvent vapor, to produce a well-ordered morphology. Here we show that under appropriate conditions, well-ordered block copolymer films may be continuously grown under substrate equilibrated conditions by slow deposition of discrete subattoliter quantities of material using electrospray. We conduct time-resolved observations and investigate the effects of process parameters that underpin film morphology including solvent selectivity, substrate temperature, block-substrate selectivity, and flow rate of the feed solution. For a PEO cylinder-forming poly(styrene-b-ethylene oxide) block copolymer, we uncover a wide temperature window from 90 to 150 °C and an ideal flow rate of 2 μL/min for ordered film deposition from dilute acetone solutions. PEO cylinders aligned with their long axes perpendicular to the film-air interface at optimal spray conditions. Using poly(styrene-b-methyl methacrylate) deposited onto neutrally selective surfaces, we show that the substrate-equilibrated process results in vertically oriented microdomains throughout the film, indicating a preservation of the initial substrate-dictated morphology during the film deposition. Electrospray offers a new and potentially exciting route for controlled, continuous growth of block copolymer thin films and manipulation of their microstructure.
authors: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States.
authors: Hanqiong
authors: H
authors: Hu
authors: Sofia
authors: S
authors: Rangou
authors: Myungwoong
authors: M
authors: Kim
authors: Padma
authors: P
authors: Gopalan
authors: Volkan
authors: V
authors: Filiz
authors: Apostolos
authors: A
authors: Avgeropoulos
authors: Chinedum O
authors: CO
authors: Osuji
mesh_terms: D003460:Crystallization / Q000379:methods*; D004595:Electroplating / Q000379:methods*; D005740:Gases / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008567:Membranes, Artificial; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D005740:Gases; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D011137:Polystyrenes; D011092:Polyethylene Glycols