A one-step process based on breath figures (BFs) that enables the preparation of nano-sized honeycomb structures on the surface of a block copolymer (BCP) film was investigated.  The process overcomes the traditional size limits of BFs.  Films with nano-sized honeycomb structures on the surface were obtained by one-step casting from cyclohexanone solution of polystyrene-b-polyethylene oxide (PS-b-PEO) under the condition of high humidity.  Water absorption by the PEO microphases of the PS-b-PEO causes these microphases to migrate to the film-air interface; hence, the PS-b-PEO can act as a template for a nano-sized structure.  The boiling point of cyclohexanone is higher than that of solvents commonly used in normal BF processes, such as carbon disulfide or chloroform, suppressing excessive water condensation and preventing water droplets from growing into the micron regime.  The combination of PS-b-PEO and cyclohexanone provides nano-sized honeycomb structures.  Meanwhile, when 1,4-dioxane, miscible with water, was used, a film with nano fibers on the surface was generated.  The large amount of water absorbed by the PS-b-PEO/1,4-dioxane solution induces the formation of PS-b-PEO micelles, resulting in the fibrous structure on the surface.  The sizes of these nano-honeycomb and nano-fiber structures can be controlled by changing molecular weight of PS-b-PEO.  The simplicity of this novel one-step method can be extended to produce advanced materials for various industrial applications by roll-to-roll processing.

One-step process for preparation of polymer films with nano-honeycomb or nano-fibers on the surface using amphiphilic block copolymer

248th National Meeting (2014)

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