para -Fluoro/thiol click chemistry-driven pentafluorostyrene-based block copolymer self-assembly: to mimic or not to mimic the solubility parameter?

International audienceA block copolymer (BCP) consisting of polystyrene (PS) and polypentafluorostyrene (PPFS) blocks is synthesized by nitroxide mediated polymerization (NMP). Then nucleophilic substitution of the labile para-fluorine atom onto the PPFS platform is performed by an organo-catalyzed reaction at ambient temperature using the para-fluoro/thiol click reaction. It is observed that the effect of the substitute chemical nature induces a drastic tuning of the nano-structuration of the block copolymer. Indeed, the para-fluoro/thiol click reaction leads to PS-b-modified PPFS block copolymers with solubility parameter control and drives an order/disorder transitio

From bio-inspired functional film to reactive nano-patterned honeycomb as a clickable platform

International audiencePorous materials are attractive for a large variety of applications with their high surface and can be designed by the "breath figure" BF method, for obtaining honeycomb HC-​structured porous films.1,​2 In addn., we have demonstrated that copolymers self-​assembly CSA can provide a second level of structure on the nano-​scale in the wall between pores,​3 leading to hierarchically structured bio-​inspired materials.4-​10 To go further, a HC film displaying three scales of hierarchy was produced for the first time with two micro- and nano-​porosities levels formed by the BF process, giving a bio-​inspired diatom exoskeleton, with a third structuration induced by the CSA between the pores (Figure 1)​. The presence of reactive nano-​domains at the film surface allowed successive chem. modifications by click chem., which induces a Cassie-​Baxter to Wenzel transition, 10 leading to a hierarchically structured reactive platform by simple click chem. 11

Sheets comprising a fluorinated polymer and presenting a variable wettability with respect to a fluid as a function of pH and/or temperature.

Sheets with the title behavior consist of a fluoropolymer matrix and block copolymer anchored to the matrix with a portion of the block copolymer having a hydrophilicity that is dependent on pH and temp. A typical sheet was manufd. by polymn. of 4-vinylpyridine in the presence of BlocBuilder in DMF at 115°, polymn. of Me methacrylate and styrene in the presence of the resulting macroinitiator, and impregnation of the resulting block copolymer into PVDF membrane

CO 2 -Driven reversible wettability in a reactive hierarchically patterned bio-inspired honeycomb film

International audienceA unique triple patterned honeycomb film with CO2-driven reversible wettability between hydrophobicity and hydrophilicity is reported in this work. The honeycomb film is prepared by directed self-assembly in “Breath Figure” (BF) templating of a PolyStyrene-b-Poly(VinylBenzylChloride) PS-b-PVBC block copolymer under a mixed water/ethanol atmosphere. Three scales of hierarchy with micro- and nano-porosities, i.e. two levels of structuration formed by the BF process, lead to a bio-inspired morphology resembling the diatom exoskeleton, while the third level is induced by the directed diblock copolymer self-assembly between the pores. Reactive PVBC surface nano-patterns are post-clicked by a melamine derivative with tertiary amino groups to drive the CO2-switchable wettability. The presence of the triple structures remarkably increases the top surface structuration, resulting in an enhanced contact angle compared with normal honeycomb films. The combination of this unique clickable patterned platform and CO2-sensitive groups endows the film with a large change in the contact angle upon CO2 stimulation. Such a smart bio-inspired honeycomb film based on a biocompatible trigger shows high application potential in bioengineering

Reactive Nanopattern in a Triple Structured Bio-Inspired Honeycomb Film

International audienceA hierarchically structured platform was obtained from spontaneous self-assembly of a poly(styrene)-b-poly(vinylbenzylchloride) (PS-b-PVBC) block copolymer (BCP) during breath figure (BF) templating. The BF process using a water/ethanol atmosphere gave a unique double porosity in which hexagonally arranged micron-sized pores were encircled by a secondary population of smaller, nano-sized pores. A third level of structuration was simultaneously introduced between the pores by directed BCP self-assembly to form out-of-the-plane nano-cylinders, offering very rapid bottom-up access to a film with unprecedented triple structure which could be used as a reactive platform for introducing further surface functionality. The surface nano-domains of VBC were exploited as reactive nano-patterns for site-specific chemical functionalization by firstly substituting the exposed chlorine moiety with azide, then “clicking” an alkyne by copper (I) catalyzed azide-alkyne Huisgen cycloaddition (CuAAC). Successful chemical modification was verified by NMR spectroscopy, FTIR spectroscopy, and XPS, with retention of the micro- and nanostructuration confirmed by SEM and AFM respectively. Protonation of the cyclotriazole surface groups triggered a switch in macroscopic behavior from a Cassie-Baxter state to a Wenzel state, highlighting the possibility of producing responsive surfaces with hierarchical structure

Reactive Nanopattern in a Triple Structured Bio-Inspired Honeycomb Film as a Clickable Platform

A hierarchically structured platform was obtained from spontaneous self-assembly of a poly(styrene)-b-poly(vinylbenzylchloride) (PS-b-PVBC) block copolymer (BCP) during breath figure (BF) templating. The BF process using a water/ethanol atmosphere gave a unique double porosity in which hexagonally arranged micron-sized pores were encircled by a secondary population of smaller, nano-sized pores. A third level of structuration was simultaneously introduced between the pores by directed BCP self-assembly to form out-of-the-plane nano-cylinders, offering very rapid bottom-up access to a film with unprecedented triple structure which could be used as a reactive platform for introducing further surface functionality. The surface nano-domains of VBC were exploited as reactive nano-patterns for site-specific chemical functionalization by firstly substituting the exposed chlorine moiety with azide, then “clicking” an alkyne by copper (I) catalyzed azide-alkyne Huisgen cycloaddition (CuAAC). Successful chemical modification was verified by NMR spectroscopy, FTIR spectroscopy, and XPS, with retention of the micro- and nanostructuration confirmed by SEM and AFM respectively. Protonation of the cyclotriazole surface groups triggered a switch in macroscopic behavior from a Cassie-Baxter state to a Wenzel state, highlighting the possibility of producing responsive surfaces with hierarchical structure

PentaFluoroStyrene-based block copolymers controlled self-assembly pattern: A platform paving the way to functional block copolymers

International audienceDiblock copolymers of 2,3,4,5,6-pentafluorostyrene (PFS) and butyl acrylate (BuA) were synthesized by nitroxide mediated polymerization (NMP). By varying the conversion and/or the BuA monomer to PPFS macro-initiator ratio, various molar compositions of the block copolymer BCP were obtained. Due to the immiscibility of both polymeric blocks, phase separation at the nanometre scale occurred. The variety of BCP synthesized gave rise to a large panel of morphologies by self-assembly. The structuration of the nanodomains of PPFS/PBuA BCPs were studied by AFM and SAXS. Nanodomain sizes ranging from 30 to 45 nm depending on the molar mass of the BCP were observed. Moreover, the lability of the fluorine atom in para position of the aromatic ring of the PFS units allows for the functionalization of the BCPs. Indeed, the para fluorine-thiol soft organo-catalysed substitution was performed with 1-hexanethiol as side group. The thermal properties and the self-assembly pattern of the BCP changes drastically by the incorporation of alkyl moiety, acting as an artificial increase of the volume fraction of the PPFS block and also matching the solubility parameter value of the PBA block, i.e. no more nano-pattern is observed by AFM and SAXS

para fluoro-thiol clicked diblock-copolymer self-assembly: Towards a new paradigm for highly proton-conductive membranes

International audienceSulfonated sPPFS-b-PBuA diblock and statistical copolymers based on 2,3,4,5,6-pentafluorostyrene PFS and butyl acrylate BuA were elaborated for Proton Exchange Membrane Water Electrolyser (PEMWE) purposes. The block copolymers (BCP) were synthetized by Nitroxide Mediated Polymerization NMP, a controlled radical polymerization technique that yields a well-defined molar mass and a low dispersity material. These diblock-copolymers have the ability to self-assemble due to the immiscibility of the two macromolecular segments PPFS and PBuA. Statistical copolymers of the similar chemical composition were synthetized by both controlled radical polymerization NMP in solution and by free radical polymerization FRP in emulsion as waterborne dispersed polymer with highest molar mass. The copolymers were sulfonated by a mild click-reaction, namely an organo-catalyzed nucleophilic substitution reaction with sodium 3-mercapto-1-propanesulfonate (SMPS) at low temperature. The morphology of the sulfonated diblock-copolymer BCP was studied by SAXS and AFM, revealing a nano-phase-segregated sulfonated membrane. The mechanical properties of the membranes were improved by ionic crosslinking with polybenzimidazole (PBI-OO). Finally, the conductive properties of the sulfonated BCPs and statistical copolymers were investigated as a function of parameters such as the morphology of the BCP, the molar mass, and the sulfonation degree of the materials