This report describes the simple preparation of superhydrophobic and lipophobic surfaces by self-organization. Microporous polymer films of a fluorinated polymer with hexagonally arranged pores were prepared by casting from solution under humid conditions. Hexagonally packed water microdroplets were formed by evaporative cooling on the surface of the casting solution. After solvent evaporation, a honeycomb-patterned polymer film was formed with the water droplet array acting as a template; the water droplets themselves evaporated soon after the solvent. Two porous polymer layers were stacked vertically, separated by pillars at the hexagon vertexes. After peeling off the top layer using adhesive tape, a pincushion-like structure was obtained. Here, we show that superhydrophobic behavior was achieved, with the maximum contact angle, 170 degrees, observed using these pincushion structures. Theoretical calculations fit the experimental results well. The lipophobic properties of the films are also discussed.
The sub-wavelength honeycomb-patterned films, which have optical transparency and superhydrophobicity, were fabricated by using condensed water droplets on the surface of a fluorinated polymer solution casting under humid conditions as the template.
Regular polymer patterns are formed from casting a dilute polymer solution on a solid substrate. Dissipative structures, e.g., convection patterns, fingering instabilities, and so on, are formed in the evaporation process of casting polymer films. Controlled production and manufacturing of patterned polymer films can be achieved when the evaporating solution edge, especially the meniscus region on the casting substrate, is formed under controlled casting conditions. In this report, we describe a computer‐controlled apparatus which has two precisely manipulated sliding glass plates. A narrow, thin liquid film of polymer solution with a receding meniscus is continuously supplied from a small gap between two glass plates (one sliding and the other stationary), and a patterned polymer film is subsequently formed on the stationary substrate from the evaporating solution edge. Several types of polymer patterns from various polymers are reproducibly prepared by changing preparation conditions such as sliding speed and polymer concentration.
Microporous polymer films with a hexagonal arrangement of pores were prepared by simple casting of various polymer solutions under humid conditions. Hexagonally packed micropores were prepared by using condensed water droplets as templates on the surface of polymer solutions. Spherical micro lens arrays (MLAs) were fabricated simply by molding from the resulting honeycomb structures. By peeling off the upper layer with adhesive tape, the pillars were severed, forming pins on each layer, and a hexagonal array of pincushion structures was generated by this procedure. Hemispherical MLAs were also fabricated by molding the pincushion structures. The hemispherical MLAs projected clearer miniaturized images than spherical MLAs.
Microporous polymer films are attractive materials with potential application in the fields of electronics,
photonics, and biotechnology. Chemical and thermal stabilities of the microporous polymer films are required
for their materials application. Besides preparation by conventional photolithography, we have reported
that honeycomb-patterned porous polymer films are prepared by a method utilizing the condensation of
small water droplets on solutions of amphiphilic copolymers. Here, we show preparation of honeycomb-patterned microporous films of a thermally and chemically stable material, polyimide. A water-template-assisted honeycomb structure was formed from a polyion complex of polyamic acids and dialkylammonium
salt. The pore size of films was controlled by the casting volume of polymer solution. The patterned polyion
complex film converted into polyimide by simple chemical treatment, keeping the porous structure. Self-supporting microporous polyimide films are fabricated. The honeycomb-structured film has high thermal
and chemical stability like that of conventional cast films of polyimides.
3D confinement effect: Block copolymers form novel phase separation structures in the nanoparticles owing to frustration of the nanosized confinement effect. Whereas films of the block copolymers form lamellar structures, the nanoparticles formed unique structures (Janus‐type, tennis‐ball‐, mushroom‐, wheel‐, and screwlike structures) depending on the ratio between particle diameter and molecular weight.
Nanoparticles with concentric layered structures were generated from a lamellae-forming poly(styrene-b-isoprene) diblock copolymer using controlled precipitation from a tetrahydrofuran/water mixture. Chloroform, a good solvent for both blocks, was used to swell and anneal the nanoparticles suspended in aqueous media. The three-dimensional morphologies of particles were reconstructed by transmission electron microtomography throughout the process of solvent annealing. A transition from concentric lamellae to PI cylinders in a PS matrix occurred upon annealing, presumably due to a slight selectivity of chloroform for PS. These cylindrical microdomains were further divided into PS-core-PI-shell spherical structures in a PS matrix upon extended annealing, a structure that is unique among reported microphase separated morphologies of diblock copolymers.
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