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We report a generic phenomenon in the ordering of block copolymer thin films, wherein the morphology spontaneously antialigns with respect to film discontinuities during thermal annealing. The aligned near-edge region propagates further from the edge with increased annealing time and temperature, while also being responsive to heating rate and applied stress fields. This effect is ascribed to a combination energetic preference for morphological orientation at boundaries as well as stress relaxation of the polymer film as it creeps orthogonal to film edges.

Electrospray deposition (ESD) enables the growth of solution deposited thin films in a precise and continuous manner by the delivery of submicron droplets of dilute solutions to a heated substrate. By combining ESD with programmable motor control and gradient solution pumping in a first-of-its-kind user tool at the Center for Functional Nanomaterials at Brookhaven National Laboratory, we show the ability to create one or two dimensional compositional gradient nanoscale films via ESD. These capabilities make it possible to construct thin film multicomponent “libraries” on a single substrate to rapidly and systematically characterize composition-dependent properties in a variety of material systems such as thin films involving homopolymer and block copolymer blends. We report the design, construction, and validation of a gradient ESD tool that allows users to carefully control the jet stability, flow composition, spray position, and substrate temperature. Calibrated thin films range in thickness from tens to hundreds of nanometers. We demonstrate gradient thin films using a ternary dye triangle as well as a gradual blending of polystyrene homopolymer with poly(styrene-block-methyl methacrylate) on a single substrate. Paired with the rapid measurement capabilities of synchrotron small angle X-ray scattering, this tool forms an integral part of a new platform for high-throughput, autonomous characterization and design of nanomaterial thin films and soft materials more generally.

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The delivery of sub-micron droplets of dilute polymer solutions to a heated substrate by electrospray atomization enabled precisely controlled and continuous deposition, or growth, of block copolymer thin films. It also provided, in principle, the ability to fabricate heterolattice materials using sequential depositions. This possibility was explored and the morphology of resulting composite films produced by such sequential electrospray deposition (ESD) of lamellar diblock copolymers of poly(styrene-b-4-vinylpyridine) with differing molecular weights was examined. The structure of the heterolattice interface was a strong function of temperature. Sharp interfaces with abrupt changes in the lamellar period were observed at lower deposition temperatures, while higher temperatures produced a smooth variation in the lamellar period from one molecular weight to the next. The ordering kinetics of a secondary high molecular weight layer could be substantially enhanced depending on the molecular weight of the polymer present in the underlying primary layer. These findings were discussed in the context of temperature and molecular weight dependent diffusion dynamics of the polymers in the melt which control the inter-mixing of the layers and therefore the structure of the heterolattice interface.