Boosted Interfacial Polarization from the Multidimensional Core–Shell–Flat Heterostructure CNP@PDA@GO/rGO for Enhanced Microwave Absorption

Heterogeneous structures have attracted extensive attention in the area of microwave absorption because they can promote interfacial polarization and thus enhance microwave absorption. Many efforts have been made in this field; however, challenges remain in terms of the absorber impedance matching and electromagnetic (EM) wave reflectivity. Herein, a multidimensional core–shell–flat heterostructure is proposed to build a kind of EM wave absorbers with both dielectric loss and magnetic loss. Polydopamine (PDA) is coated on the surface of nanoscale carbonyl nickel powder (CNP) to obtain the core–shell structure of CNP@PDA nanoparticles, and then, the CNP@PDA nanoparticles are grafted around graphene oxide (GO)/reduced GO (rGO) or sandwiched between the layers of GO/rGO to form a core–shell–flat heterostructure. Two-dimensional GO/rGO and three-dimensional PDA can modulate the impedance matching of nano-CNP and enhance the interfacial polarization of the absorber. The reflection loss of ternary CNP@PDA@GO/rGO is better than that of binary CNP@PDA or CNP@GO due to the interfacial polarization and multiple interfacial scattering of the heterostructure. The minimum reflection loss can reach −70.7 dB with a thickness of 2.5 mm, while the efficient absorption bandwidth (≤−10 dB) can achieve 8.5 GHz. The heterojunction contacts constructed by CNP–PDA and PDA–GO/rGO contribute to the enhanced polarization loss and interfacial reflection loss. The mechanism of excellent EM wave absorption is explained by enhanced interfacial polarization, interface scattering, and adjusted impedance matching. These results pave the way to fabricate high-performance EM wave absorption materials with a controlled multidimensional morphology and balanced impedance matching

Photochemically Driven Polymeric Biocompatible and Antimicrobial Thiol–Acrylate Nanocomposite Suitable for Dental Restoration

The development a photochemically driven polymeric composite for dental restorative materials to restore tooth cavities with antibacterial, biocompatibility, and outstanding mechanical properties is an urgent need for clinical application in stomatology. Herein, a series of polyurethane acrylate (PUA) prepolymers and antibacterial polyurethane acrylate quaternary ammonium salts (PUAQASs) were synthesized, and their mechanical and biological properties were explored. The unique secondary mercaptan with a long shelf life and low odor was used to reduce oxygen inhibition and increase cross-linking density; meanwhile, modified photocurable nano zirconia (nano ZrO2) enhances mechanical properties of the nanocomposites and possesses preeminent dispersion in the matrix. The results show that minimal inhibitory concentrations (MICs) of PUAQASs are 200 and 800 μg/mL for Staphylococcus aureus and Escherichia coli, respectively. The addition of secondary thiols significantly increases the photopolymerization rate and monomer conversion. The highest hardness and modulus reach 1.8 and 8.7 GPa compared to 1.8 and 8.3 GPa for commercial resin. The lap shear stress on the pig bone is 912 MPa, and that on commercial resin is 921 MPa. Most importantly, the photochemically driven polymeric composite has excellent biocompatibility and significantly better antimicrobial properties than commonly used commercial resins

Polyurethane acrylate-supported rGO/TiO₂ electrical conductive and antibacterial nanocomposites

Polyurethane acrylate (PUA)-supported rGO/TiO2 electrical conductive and antibacterial nanocomposites were synthesized via in-situ polymerization. The well-dispersed rGO/TiO2 can serve as photoinitiator and give PUA material antibacterial property at the same time. The excellent UV-curing and antibacterial activity could be explained that the synergistic effect of rGO and TiO2, which could promote the effective electron/hole separation and thus generate various reactive species. After dopped the rGO/TiO2 into the PUA matrix, the PUA film became electric conductive. The obtained nanocomposites will have promising applications in high performance antibacterial coatings.</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

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

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

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