Stimuli-responsive polymer/metal composites: From fundamental research to self-regulating devices

Light-Driven Spatiotemporal Pickering Emulsion Droplet Manipulation Enabled by Plasmonic Hybrid Microgels

The past decades have witnessed the development of various stimuli-responsive materials with tailored functionalities, enabling droplet manipulation through external force fields. Among different strategies, light exhibits excellent flexibility for contactless control of droplets, particularly in three-dimensional space. Here, we present a facile synthesis of plasmonic hybrid microgels based on the electrostatic heterocoagulation between cationic microgels and anionic Au nanoparticles. The hybrid microgels are effective stabilizers of oil-in-water Pickering emulsions. In addition, the laser irradiation on Au nanoparticles creats a "cascade effect" to thermally responsive microgels, which triggers a change in microgel wettability, resulting in microgel desorption and emulsion destabilization. More importantly, the localized heating generated by a focused laser induces the generation of a vapor bubble inside oil droplets, leading to the formation of a novel air-in-oil-in-water (A/O/W) emulsion. These A/O/W droplets are able to mimic natural microswimmers in an aqueous environment by tracking the motion of a laser spot, thus achieving on-demand droplet merging and chemical communication between isolated droplets. Such proposed systems are expected to extend the applications of microgel-stabilized Pickering emulsions for substance transport, programmed release and controlled catalytic reactions.

Platinum-coated silicotungstic acid-sulfonated polyvinyl alcohol-polyaniline based hybrid ionic polymer metal composite membrane for bending actuation applications

An electro-stimulus-responsive bending actuator was developed by synthesizing a non-perfluorinated membrane based on silicotungstic acid (SA), sulfonated polyvinyl alcohol (SPVA), and polyaniline (PANI). The membrane was developed via solution casting method. The dry membrane SA/SPVA showed a sufficient ion-exchange potential of 1.6 meq g⁻¹ dry film. The absorption capacity of the membrane after almost 6 h of immersion was found to be ca. 245% at 45 °C. The electroless plating with Pt metal was carried out on both sides of the membrane that delivered an excellent proton conductivity of 1.9 × 10⁻³ S cm⁻¹. Moreover, the scanning electron microscopy (SEM) was conducted to reflect the smooth and consistent surface that can prevent water loss. The water loss capacity of the membrane was found to be ca. 33% at 6 V for 16 min. These results suggest a good actuation output of the ionic polymer metal composite (IPMC) membrane once the electrical potential is applied. The electromechanical characterization displayed a maximum tip displacement of 32 mm at 3 V. A microgripping device based on multifigure IPMC membrane may be developed showing a good potential in micro-robotics.

Preparation, Properties, and Microbial Impact of Tungsten (VI) Oxide and Zinc (II) Oxide Nanoparticles Enriched Polyethylene Sebacate Nanocomposites

Nanoparticles of tungsten oxide (WO₃) and zinc oxide (ZnO) enriched polyethylene sebacate (PES) nanocomposites were prepared through the coprecipitation process and condensation polymerization reaction. The obtained nano-sized particles of WO₃ and ZnO, PES, and nanocomposites (WO₃-PES NC and ZnO-PES NC) were investigated. The average molecular weight of the cured PES was measured by employing the gel permeation chromatography (GPC) technique. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) spectra assured the formation of the polymeric nanocomposites.WO₃ and ZnO nanoparticles supposed a condensed porous spherical phase found implanted in the polymer structure, as detected by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. These nano-scale systems achieved an electrical activity based on the conductive nanoparticles embedded matrix as a result of the ion-ion interactions. The microbial influence of the nanocomposites was examined against pathogenic bacteria; Pseudomonas aeruginosa,Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, and Fungi; Aspergillus niger, and Candidaalbicans. Results exhibited that these nanocomposites have antimicrobial effects from moderate to slightly high on bacteria and high on fungi which was confirmed by a clear zone of inhibition. This study contributes to the design of reasonable composites to be under evaluation for their catalytic effect.