Nanoporous thin films from ionically connected diblock copolymers

An ionically connected polystyrene-block-poly(ethylene oxide) diblock copolymer (PS−+PEO) has been prepared by blending a PEO block functionalized by a dimethylamino group at one extremity with a sulfonic acid terminated PS block. Proton transfer occurs from the sulfonic acid to the dimethylamino group, resulting in the formation of an ion pair acting as a junction between the two polymer blocks. This copolymer was further used to prepare thin films with a cylindrical morphology consisting of PEO cylinders embedded in a PS matrix and oriented perpendicularly to the film surface. Nanoporous thin films with sulfonate groups on the pore walls have been finally obtained after solvent extraction of the PEO microphases. The presence of those sulfonate groups was evidenced by grafting a positively charged fluorescent dye on the pore walls.

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► A sulfonic acid-ended polystyrene (PS) was mixed to an amino-ended poly(ethylene oxide) (PEO).
► An ionically connected block copolymer was directly formed.
► A thin film showing PEO cylinders embedded in a PS matrix was obtained.
► Nanoporosity was created by removing PEO blocks by a solvent extraction process.