Preparation, mechanical properties, fatigue and tribological behavior of double crosslinked high strength hydrogel

Polyvinyl alcohol hydrogel (PVA-H) has been widely used in clinical transplantation because of its high water content, good biocompatibility and mechanical properties. However, PVA-H have some problems, such as low elongation at break, low fatigue resistance and high friction coefficient, which hinders its application in clinic. In this paper, a novel high-performance PVA hydrogel enhanced by chemical double crosslinking (CDC) method had been synthesized. The influences of chemical crosslinking agent concentration on mechanical properties, friction properties and fatigue properties of materials were systematically investigated, in order to meet the clinical application of artificial meniscus, artificial cartilage, nucleus pulposus and so on. As a result, due to the introduction of chemical bonds, CDC hydrogels have over 600% elongation at break, modulus loss after fatigue test was reduced by 42%, average coefficient during friction was reduced to 0.048, and biocompatibility performance was excellent. The PVA hydrogel enhanced by CDC method provides a new concept for us to prepare high-performance PVA hydrogel and a promising material to replace cartilage, meniscus, nucleus pulposus and other tissues.

Design of Nanostructured Protective Coatings with a Sensing Function

Nanostructured multilayered coatings for metals are prepared to simultaneously provide a function of corrosion mitigation and of corrosion sensing for copper substrates. Silica nanocapsules, embedded in one layer of the coating, are used as a host for a corrosion inhibitor and as a sensor, which detect changes of pH value and release inhibitors via an optical signal. Furthermore, another layer in the coating exists in a nanonetwork loaded with another corrosion inhibitor, which is impregnated with a hydrophobic polymer. We demonstrate that a specific arrangement of layers leads to an optimum anticorrosion and sensing performance while the sensing signal can be prolonged for a long time. It is the first time that the fluorophore detecting corrosion is conjugated to the nanosensor and that nanofibers and nanocapsules are used simultaneously to load and release corrosion inhibitors for anticorrosion applications.

Chemical Vapor Deposition of Thin, Conductive, and Fouling-Resistant Polymeric Films

Fouling has been a persistent issue within applications ranging from membrane separation to biomedical implantation. Research to date focuses on fouling-resistant coatings, where electrical conductivity is unnecessary. In this study, we report the synthesis of multifunctional thin films with both fouling resistance and electrical conductivity for their potential applications in the electrolysis-based self-cleaning of separation membranes and in the field of bioelectronics. This unique combination of properties results in multifunctional coatings that are a zwitterionic derivative of intrinsically conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) synthesized via oxidative chemical vapor deposition (oCVD). Their fouling resistance is shown to be comparable to that of known dielectric fouling-resistant surfaces, such as a poly(4-vinylpyridine)-co-divinylbenzene (p4VP-DVB)-derived zwitterionic coating, an amphiphilic poly(1H,1H,2H,2H-perfluorodecyl acrylate-co-2-hydroxyethyl methacrylate) (pPFDA-HEMA) coating, and a glass surface, and are far superior to the fouling resistance of gold or polydimethylsiloxane (PDMS) surfaces. The fouling resistances of seven surfaces are quantitatively characterized by molecular force probe (MFP) analysis. In addition, four-point probe electrical measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), variable-angle spectroscopic ellipsometry (VASE), profilometry, water contact angle (WCA) measurements, surface ζ-potential measurements, and atomic force microscopy (AFM) were employed to characterize the physiochemical properties and morphology of the different surfaces.

Manipulating Migration Behavior of Magnetic Graphene Oxide via Magnetic Field Induced Casting and Phase Separation toward High-Performance Hybrid Ultrafiltration Membranes

Hybrid membranes blended with nanomaterials such as graphene oxide (GO) have great opportunities in water applications due to their multiple functionalities, but they suffer from low modification efficiency of nanomaterials due to the fact that plenty of the nanomaterials are embedded within the polymer matrix during the blending process. Herein, a novel Fe3O4/GO-poly(vinylidene fluoride) (Fe3O4/GO-PVDF) hybrid ultrafiltration membrane was developed via the combination of magnetic field induced casting and a phase inversion technique, during which the Fe3O4/GO nanocomposites could migrate toward the membrane top surface due to magnetic attraction and thereby render the surface highly hydrophilic with robust resistance to fouling. The blended Fe3O4/GO nanocomposites migrated to the membrane surface with the magnetic field induced casting, as verified by X-ray photoelectron spectroscopy, elemental analysis, and energy dispersive X-ray spectroscopy. As a result, the novel membranes exhibited significantly improved hydrophilicity (with a contact angle of 55.0°) and water flux (up to 595.39 L m(-2) h(-1)), which were improved by 26% and 206%, 12% and 49%, 25% and 154%, and 11% and 33% compared with those of pristine PVDF membranes and PVDF hybrid membranes blended with GO, Fe3O4, and Fe3O4/GO without the assistance of magnetic field during membrane casting, respectively. Besides, the novel membranes showed high rejection of bovine serum albumin (>92%) and high flux recovery ratio (up to 86.4%). Therefore, this study presents a novel strategy for developing high-performance hybrid membranes via manipulating the migration of nanomaterials to the membrane surface rather than embedding them in the membrane matrix.