UV-curable polyurethane acrylate–Ag/TiO₂ nanocomposites with superior UV light antibacterial activity

<p>Polyurethane acrylate (PUA)–Ag/TiO₂ nanocomposites were synthesized through in situ polymerization. The well-dispersed Ag/TiO₂ nanorods serve as photoinitiator. Meanwhile, the PUA–Ag/TiO₂ nanocomposite films exhibit superior activity toward the photocatalytic degradation of <i>Escherichia coli</i> under UV light. The excellent UV curing and antibacterial activities can be ascribed to the synergistic effect of Ag and TiO₂, which promotes the effective electron/hole separation and thus generates various reactive species. Thin films with these nanoparticles are more hydrophilic after UV illumination. And the antibacterial mechanism of the UV-curable PUA–Ag/TiO₂ nanocomposites was proposed.</p

Effects of Surface Structure and Morphology of Nanoclays on the Properties of Jatropha Curcas Oil-Based Waterborne Polyurethane/Clay Nanocomposites

Three kinds of nanoclays with different structure and morphology were modified by γ-amino­propyl­triethoxysilane (APTES) and then incorporated into Jatropha oil-based waterborne polyurethane (WPU) matrix via in situ polymerization. The effects of surface structure and morphology of nanoclay on the degree of silylation were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA). The results showed that the montmorillonite (MT) with abundant hydroxyl group structure and platelet-like morphology had the highest degree of silylation, while the modified halloysite nanotubes (HT) had the lowest grafting ratio. The effects of different silylated clays on the properties of WPU/clay nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), TGA, dynamic thermomechanical analysis (DMA) and tensile testing machine. SEM images showed that all silylated clays had good compatibility with WPU and were uniformly dispersed into the polymer matrix. WPU/SMT exhibited the best thermal properties owing to its intercalated structure. Dynamic thermomechanical analysis (DMA), atomic force microscope (AFM), and water contact angle results demonstrated that the silylated nanoclays enhanced the degree of microphase separation, surface roughness, and hydrophobicity of WPU/clay nanocomposites

Zwitterion-Modified Nanogel Responding to Temperature and Ionic Strength: A Dissipative Particle Dynamics Simulation

The self-assembly and stimuli-responsive properties of nanogel poly(n-isopropylacrylamide) (p(NIPAm)) and zwitterion-modified nanogel poly(n-isopropylacrylamide-co-sulfobetainemethacrylate) (p(NIPAm-co-SBMA)) were explored by dissipative particle dynamics simulations. Simulation results reveal that for both types of nanogel, it is beneficial to form spherical nanogels at polymer concentrations of 5–10%. When the chain length (L) elongates from 10 to 40, the sizes of the nanogels enlarge. As for the p(NIPAm) nanogel, it shows thermoresponsiveness; when it switches to the hydrophilic state, the nanogel swells, and vice versa. The zwitterion-modified nanogel p(NIPAm-co-SBMA) possesses thermoresponsiveness and ionic strength responsiveness concurrently. At 293 K, both hydrophilic p(NIPAm) and superhydrophilic polysulfobetaine methacrylate (pSBMA) could appear on the outer surface of the nanogel; however, at 318 K, superhydrophilic pSBMA is on the outer surface to cover the hydrophobic p(NIPAm) core. As the temperature rises, the nanogel shrinks and remains antifouling all through. The salt-responsive property can be reflected by the nanogel size; the volumes of the nanogels in saline systems are larger than those in salt-free systems as the ionic condition inhibits the shrinkage of the zwitterionic pSBMA. This work exhibits the temperature-responsive and salt-responsive behavior of zwitterion-modified-pNIPAm nanogels at the molecular level and provides guidance in antifouling nanogel design

Highly Flexible, Freezing-Resistant, Anisotropically Conductive Sandwich-Shaped Composite Hydrogels for Strain Sensors

Anisotropically conductive hydrogels have promising applications in artificial intelligence and wearable flexible electronics. However, for conductive hydrogels, the integration of comprehensive properties, such as high electrical conductivity, strong moisture retention, and high mechanical properties, is very important. In this article, sandwich-shaped anisotropically conductive hydrogels were constructed with a conductivity of up to 1.5 S/m. The difference in conductivity along the different directions is about a factor of 6. The formation of dynamic coordination bonding enhances the cross-linked network between poly(acrylic acid) and Nd3+, which causes the hydrogels to have excellent self-healing properties and fatigue resistance, with a self-healing efficiency of up to 90%. The middle layer of the hydrogels is compounded with nanographene, which cuases the hydrogels to have good mechanical properties, such as ultrastretchability (∼1930%) and high strength (∼0.7 MPa). The binary solvent consisting of glycerin and water gives the hydrogels an excellent moisturizing and antifreezing function. It maintains good flexibility and conductivity even at −18 °C. Based on the rapid response and high sensitivity, the sandwich-shaped hydrogel strain sensors can detect human motion (such as knuckle motion, wrist movement, etc.), showing great application potential in flexible sensors

Zwitterion-Modified Nanogel Responding to Temperature and Ionic Strength: A Dissipative Particle Dynamics Simulation

The self-assembly and stimuli-responsive properties of nanogel poly(n-isopropylacrylamide) (p(NIPAm)) and zwitterion-modified nanogel poly(n-isopropylacrylamide-co-sulfobetainemethacrylate) (p(NIPAm-co-SBMA)) were explored by dissipative particle dynamics simulations. Simulation results reveal that for both types of nanogel, it is beneficial to form spherical nanogels at polymer concentrations of 5–10%. When the chain length (L) elongates from 10 to 40, the sizes of the nanogels enlarge. As for the p(NIPAm) nanogel, it shows thermoresponsiveness; when it switches to the hydrophilic state, the nanogel swells, and vice versa. The zwitterion-modified nanogel p(NIPAm-co-SBMA) possesses thermoresponsiveness and ionic strength responsiveness concurrently. At 293 K, both hydrophilic p(NIPAm) and superhydrophilic polysulfobetaine methacrylate (pSBMA) could appear on the outer surface of the nanogel; however, at 318 K, superhydrophilic pSBMA is on the outer surface to cover the hydrophobic p(NIPAm) core. As the temperature rises, the nanogel shrinks and remains antifouling all through. The salt-responsive property can be reflected by the nanogel size; the volumes of the nanogels in saline systems are larger than those in salt-free systems as the ionic condition inhibits the shrinkage of the zwitterionic pSBMA. This work exhibits the temperature-responsive and salt-responsive behavior of zwitterion-modified-pNIPAm nanogels at the molecular level and provides guidance in antifouling nanogel design