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Selective confinement of oleylamine capped Au nanoparticles in self-assembled PS-b-PEO diblock copolymer templates

Amphiphilic polystyrene-block-polyethylene oxide (PS-b-PEO) block copolymers (BCPs) have been demonstrated to be effective in directing organization of colloidal Au nanoparticles (NPs). Au NPs have been incorporated into the polymer and the different chemical affinity between the NP surface and the two blocks of the BCP has been used as a driving force of the assembling procedure. The morphology of the nanocomposites, prepared and fabricated as thin films, has been investigated by means of atomic force and scanning electron microscopies as a function of the NP content and BCP molecular weight. NPs have been effectively dispersed in PS-b-PEO hosts at any investigated content (up to 17 wt%) and a clear effect of the BCP properties on the final nanocomposite morphology has been highlighted. Finally, electrostatic force microscopy has demonstrated the conductive properties of the nanocomposite films, showing that the embedded Au NPs effectively convey their conductive properties to the film. The overall investigation has confirmed the selective confinement of the as-prepared surfactant-coated metal NPs in the PS block of PS-b-PEO, thus proposing a very simple and prompt assembling tool for nanopatterning, potentially suitable for optoelectronic, sensing and catalysis applications.

Optical and Conductive Properties of As-Synthesized Organic-Capped TiO2 Nanorods Highly Dispersible in Polystyrene-block-poly(methyl methacrylate) Diblock Copolymer

As-synthesized organic-capped TiO2 nanorods were incorporated into polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer to achieve TiO2/PS-b-PMMA nanocomposites with enhanced optical and conductive properties. The specific surface chemistry of TiO2 nanorods derived from the colloidal synthetic approach allowed their prompt incorporation in the PS-b-PMMA block copolymer template up to 50 wt %, which resulted in films with an extended coverage of highly dispersed nanoparticles for contents higher than 30 wt %. At such high nanorod contents, the films fabricated by the prepared nanocomposites demonstrated enhanced optical properties. Atomic force microscopy investigation of the nanocomposite films showed a cylindrical morphology for low nanorod contents. Conversely, higher nanorod contents resulted upon removal of the organic component in the nanocomposites with UV treatment in overall nanorod coverage of the film surface with the concomitant formation of charge percolation paths, which led to noticeable conductivity values. EFM and PF-TUNA measurements confirmed the conductive properties of the composites at nanoscale, whereas semiconductor analyzer measurements provided their macroscale characterization. In addition, an increase in the UV-vis absorption was observed with the increase in the nanorod content along with a remarkable conductivity of the overall film.

Enhancement of the mechanical properties at the macro and nanoscale of thermosetting systems modified with a polystyrene-block-polymethyl methacrylate block copolymer

A diglycidyl ether of bisphenol A (DGEBA) epoxy monomer-based thermosetting system modified with a varying content of a polystyrene-block-polymethyl methacrylate (PS-b-PMMA) block copolymer and cured with a 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) curing agent was prepared by two different methods, without and with a solvent for the previous solution of the PS-b-PMMA block copolymer. The influence of the modifier content as well as the preparation method on the final properties of the PS-b-PMMA/(DGEBA-MCDEA) cured systems was investigated. DSC characterization confirmed the miscibility of the block copolymer with the thermoset matrix. Regardless of the preparation method, all analyzed thermosetting systems modified with PS-b-PMMA showed a nanostructured morphology, as confirmed by AFM measurement. The mechanical properties studied by a universal testing machine (MTS) at the macroscale were enhanced by the addition of the PS-b-PMMA block copolymer, especially in terms of the fracture toughness which improved considerably up to 25 wt% PS-b-PMMA content, although also the flexural modulus presented a slight increase with the modification with the PS-b-PMMA block copolymer. The quantitative nanomechanical (QNM) properties were studied at the nanoscale by AFM in PeakForce mode, and showed an improvement of the elastic modulus of the PMMA/(DGEBA-MCDEA) matrix up to 25 wt% PS-b-PMMA content. The QNM results allowed also the detection of a high difference between the elastic modulus values corresponding to the microseparated PS block rich phase and the PMMA/(DGEBA-MCDEA) matrix. A similar tendency was exhibited for both preparation methods, although the thermosetting systems prepared with the solvent reached slightly higher elastic moduli.