Selectivity of a Copper Oxide CO2 Reduction Electrocatalyst Shifted by a Bioinspired pH-Sensitive Polymer

A bioinspired polymeric membrane capable of shifting the selectivity of a copper oxide electrocatalyst in the CO2 reduction reaction is described. The membrane is deposited on top of copper oxide thin films from wet deposition techniques under controlled conditions of humidity and self-assembles into an arranged network of micrometer-sized pores throughout the polymer cross-section. The membrane was composed of a block copolymer with a precisely controlled ratio of poly-4-vinylpyridine and poly(methyl methacrylate) blocks (PMMA-b-P4VP). The intrinsic hydrophobicity, together with the porous nature of the membrane's surface, induces a Cassie-Baxter wetting transition above neutral pH, resulting in water repulsion from the catalyst surface. As a consequence, the catalyst's surface is shielded from surrounding water molecules under CO2 electroreduction reaction conditions, and CO2 molecules are preferentially located in the vicinity of the catalytically active area. The CO2 reduction reaction is therefore kinetically favored over the hydrogen evolution reaction (HER).

Poly(N,N-diethylacrylamide)-endowed spontaneous emulsification during the breath figure process and the formation of membranes with hierarchical pores

The spontaneous emulsification for the formation of water-in-oil (W/O) or oil-in-water (O/W) emulsions needs the help of at least one kind of the third component (surfactant or cosolvent) to stabilize the oil-water interface. Herein, with the water/CS2-soluble polymer poly(N,N-diethylacrylamide) (PDEAM) as a surfactant, the spontaneous formation of water-in-PDEAM/CS2 emulsions is reported for the first time. The strong affinity between PDEAM and water or the increase of PDEAM concentration will accelerate the emulsification process with high dispersed phase content. It is demonstrated that the spontaneous emulsification of condensed water droplets into the PDEAM/CS2 solution occurs during the breath figure process, resulting in porous films with two levels of pore sizes (i.e., micron and submicron). The emulsification degree and the amounts of submicron-sized pores increase with PDEAM concentration and solidifying time of the solution. This work brings about incremental interest in spontaneous emulsification that may happen during the breath figure process. The combination of these two simultaneous processes provides us with an option to build hierarchically porous structures with condensed and emulsified water droplets as templates. Such porous membranes may have great potential in fields such as separation, cell culture, and biosensing.

Fabrication of Adsorption-Type Hierarchical Functional Films by Using a Facile Swollen Based Breath Figure Method

The morphology transition from primary to hierarchical adsorption-type microporous domains of amphiphilic block copolymer (BCP) honeycomb-structured films is demonstrated by a facile swollen based breath figure (BF) method. The characteristic parameters of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) hierarchical micro- and submicro-porous films can be controlled by changing the length of segments or subsequent swelling conditions. A plausible mechanism is demonstrated in this research. A typical amphiphilic BCP with very low volume content of hydrophilic blocks (f_P4VP ≤ 0.050) can efficiently stabilize water droplets and inherently assist in the formation of morphology transition. This BCP film can be used for Cr(VI) removal from wastewater, which additionally has enormous potential application in the field of novel optical devices, soft lithography, size-selective separation, etc. This article is protected by copyright. All rights reserved.

Functional Nanoparticles-driven Self-assembled Diblock Copolymer Hybrid Nano-Patterns

Herein, we report how functional gold nanoparticles can drive the block copolymer BCP thin film morphologies of polystyrene-block-poly(vinylbenzyl-3-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)prop-1-yne (PS-b-PVBEG). PS-b-PVBEG was obtained via Nitroxide Mediated Polymerization and two consecutive post-polymerization...

CO2-Triggered ON/OFF Wettability Switching on Bioinspired Polylactic Acid Porous Films for Controllable Bioadhesion

Bioinspired honeycomb-like porous films with switchable properties have drawn much attention recently owing to their potential application in scenarios in which the conversion between two opposite properties is required. Herein, the CO₂-gas-triggered ON/OFF switching wettability of biocompatible polylactic acid (PLA) honeycomb porous films is fabricated. Highly ordered porous films with diameters between 2.0 and 2.8 μm are separately prepared from complexes of nonresponsive PLA and a CO₂-sensitive melamine derivative [N²,N⁴,N⁶-tris(3-(dimethylamino)propyl)-1,3,5-triazine-2,4,6-triamine, MET] via the breath figure method. The hydrophilic CO₂-sensitive groups can be precisely arranged in the pore's inner surface and/or top surface of the films by simply changing the PLA/MET ratio. The sensitive groups in the pore's inner surface act as a switch triggered by CO₂ gas controlling water to enter the pores or not, thus resulting in ON/OFF switching wettability. The largest response of the water contact angle of honeycomb films reaches 35°, from 100 to 65°, leading to an obvious hydrophobic-hydrophilic conversion. The improved surface wettability enhances the interaction between the cell and honeycomb film surface, thus resulting in a better cell attachment. Such smart properties accompanying the biocompatible polymer and biological gas trigger facilitate possible biomedical and bioengineering applications in the future for these films.

When a pH-triggered nanopatterned shape transition drives the wettability of a hierarchically self-organized film: A bio-inspired effect of "sea Anemone"

HYPOTHESIS

Hierarchically structured surfaces including sensitive materials presents the advantage to exalt wettability variation due to the combination of micro structure effect directed by Cassie Baxter and/or Wenzel behaviour which is tuned by the surface energy variation of sensitive polymer films.

EXPERIMENTS

Herein is reported the synthesis and the hierarchical structuration of a pH sensitive diblock copolymer P(S-stat-MMA)-b-P4VP with a pH-sensitive Poly 4-vinylpyridine P4VP block. Applying the Breath Figure method casting (minute time scale process), this diblock copolymer allows to obtain a micro porous honeycomb film while a wall nano-structuration due to self-assembly of diblock copolymer is observed.

FINDINGS

The pH-triggered wettability is studied and correlated with the morphology evolution of P4VP nano-domains investigated by AFM in a liquid cell. Indeed, a nano-dots to nano-rings/donuts transition is highlighted when decreasing the pH below the pKa of the P4VP. This nano "sea Anemone" shape transition induces the macroscopic changes of the wettability of a hierarchically self-organized honeycomb film, explained by the protonation of P4VP chains inducing electrostatic repulsion and then hydrophilic surface.

A nanopatterned dual reactive surface driven by block copolymer self-assembly

Herein, we report the selective functionalization of nano-domains obtained by the self-assembly of a polystyrene-block-poly(vinyl benzyl azide) PS-b-PVBN₃ copolymer synthesized in three steps. First, a polystyrene macro-initiator was synthesized, and then extended with vinyl benzyl chloride by nitroxide mediated polymerization to form polystyrene-block-poly(vinyl benzyl chloride) PS-b-PVBC. Nucleophilic substitution of vinyl benzyl chloride into a vinyl benzyl azide moiety is finally performed to obtain PS-b-PVBN₃ which self-assembled into nano-domains of vinyl benzyl azide PVBN₃. Click chemistry was then used to bind functional gold nanoparticles and poly(N-isopropylacrylamide) (PNIPAM) on PVBN₃ domains due to the specific anchoring at the surface of the nanopatterned film. Atomic force microscopy (AFM) was used to observe the block copolymer self-assembly and the alignment of the gold nanoparticles at the surface of the PVBN₃ nanodomains. Thorough X-ray photoelectron spectroscopy (XPS) analysis of the functional film showed evidence of the sequential grafting of nanoparticles and PNIPAM. The hybrid surface expresses thermo-responsive properties and serves as a pattern to perfectly align and control the assembly of inorganic particles at the nanoscale.

Direct formation of hydrophilic honeycomb film by self-assembly in breath figure templating of hydrophobic polylacticacid/ionic surfactant complexes

Honeycomb-patterned porous films with good surface wettability have great potential applications in various areas. However, hydrophilic honeycomb films are difficult to obtain using the direct self-assembly of pure (co)polymers. Thus, additional and special treatments are required to improve film wettability, which makes the procedure complicated and difficult to access. In this study, a facile way to prepare hydrophilic honeycomb-structured porous films is proposed that uses the direct self-assembly of complexes of biocompatible hydrophobic poly(l-lactic acid) and dodecyltrimethylammonium chloride by breath figure templating. The addition of ionic surfactant not only improves film quality but also confers good wettability. The obtained hydrophilic pore arrays were found to effectively promote cell attachment. Such a hydrophilic honeycomb-patterned porous film could find potential applications where pore wetting is required, including tissue engineering, lithography, and nanoparticle embedding.

Cell adhesion and proliferation in chiral pores triggered by polyoxometalates

The chirality of polyoxometalate anchoring in the cavity of pitted films was demonstrated to strongly influence the adhesion and proliferation of E. coli cells.

CO2-Driven reversible wettability in a reactive hierarchically patterned bio-inspired honeycomb film

A triple structured honeycomb film is fabricated through block copolymer directed self-assembly in “Breath Figure” templating as a clickable patterned platform to enhance its reversible surface wettability between hydrophobicity and hydrophilicity upon a biological CO₂ trigger.