Highly Adhesive and Self-Healing Zwitterionic Hydrogels as Antibacterial Coatings for Medical Devices.

Bacterial infection of medical devices has caused incalculable losses to maintenance costs and health care. A single coating with antibacterial function cannot guarantee the long-term use of the device, because the coating will be damaged and fall off during reuse. To solve this problem, the development of coatings with high adhesion and self-healing ability is a wise direction. In this paper, a multifunctional polyzwitterionic antibacterial hydrogel coating (PZG) composed of amphozwitterion monomer, anionic monomer, and quaternary ammonium cationic monomer was synthesized by dipping UV photoinitiated polymerization. The structure of PZGs was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Ascribing to the hydrogel internal electrostatic interaction, hydrogen bond, and cation-π interaction, the obtained PZGs exhibited high ductility (>1200% strain) and appropriate strength (>189 kPa). Remarkably, PZGs could also adhere firmly on different substrates through noncovalent interaction, and their adhesion could be controlled by adjusting the amount of zwitterionic. Reversible physical interactions in polymer networks endowed hydrogels with excellent self-healing properties. In addition, PZGs exhibit good antibacterial activity and biocompatibility due to the synergistic effect of quaternary ammonium cation and amphozwitterion monomer. This work provides a multifunctional antibacterial coating for medical equipment and has broad application prospects in the biomedical field.

Self-Symmetrical 3D Hierarchical α-Calcium Sulfate Hemihydrate Twin-Flowers Composed of Microplates as a Renewable Material for Water Separation from Water-in-Oil Emulsion.

Novel three-dimensional hierarchical α-calcium sulfate hemihydrate twin-flowers with a self-symmetrical structure (3D α-HH HTFs) are synthesized successfully assisted by trisodium citrate (TSC). The morphology of α-HH is closely dependent on TSC, and with increasing TSC concentration from 0 to 15 mM, the morphology gradually evolves from a long column to rod, hexagonal plate, twin-flower-like, and eventually microgranule. 3D α-HH HTFs are formed via heterogeneous nucleation coupled with Ostwald ripening. The 3D α-HH HTFs are further used as an immobilized water material to separate water from a surfactant-stabilized water-in-oil emulsion, and exhibit excellent separation performance with a separation efficiency of 99.31 wt % and immobilization efficiency of 93.03 wt %. Impressively, the separated solid after water separation can be regenerated into 3D α-HH HTFs, which retain the high separation performance of the original 3D α-HH HTFs. This work demonstrates that 3D α-HH HTFs are highly promising in purifying oil with undesired water contamination.

Polyaniline-Decorated Supramolecular Hydrogel with Tough, Fatigue-Resistant, and Self-Healable Performances for All-In-One Flexible Supercapacitors.

It is a challenge to realize high strength, toughness, and energy storage, as well as excellent capacitive self-recovery, fatigue-resistant, and self-healing performances simultaneously in a single all-in-one supercapacitor aiming for wearable electronics. Herein, based on the self-crosslinking and molecular template, a supramolecular poly(vinyl alcohol)/poly (N-hydroxyethyl acrylamide) (PVA/PHEA) hydrogel electrolyte (HGE) decorated by polyaniline (PANI) was prepared by in situ rapid polymerization of high-concentration aniline on the PVA/PHEA gel containing H2SO4. The multiple hydrogen bonds, rapid polymerization, and decoration endowed PANI-decorated PVA/PHEA HGE-based all-in-one flexible supercapacitor with the integrated high performances, which include high specific capacitance, good cycling stability, high strength, excellent toughness, rapid self-recovery, excellent fatigue-resistant, and self-healing capabilities, as well as high capacitance retention during or after the large deformations or after the self-healing. Thus, the current work presents a novel and promising strategy to design the integrated high-performance supercapacitors aiming for wearable electronics.

Aspect ratio-controlled preparation of α-CaSO4·0.5H2O from phosphogypsum in potassium tartrate aqueous solution.

In this study, a simple and efficient strategy is developed to synthesize rod-shaped α-CaSO4·0.5H2O crystals with tunable aspect ratio from industrial phosphogypsum only in potassium tartrate aqueous solution at a low temperature. Industrial phosphogypsum can be effectively converted into rod-shaped α-CaSO4·0.5H2O crystals with the assistance of potassium tartrate, and the aspect ratio of α-CaSO4·0.5H2O crystals gradually decreases from 52 : 1 to 1 : 1 with increasing the concentration of potassium tartrate. The formation process of the rod-shaped α-CaSO4·0.5H2O crystals in this system involves the dissolution of CaSO4·2H2O and nucleation of α-CaSO4·0.5H2O crystals. The tartrate ions from potassium tartrate in this system preferentially bind to (001) and (002) facets of α-CaSO4·0.5H2O crystals, inhibiting the growth of α-CaSO4·0.5H2O crystals along the c-axis and controlling its morphology and aspect ratio.

Effect of Cu2+ on the nucleation kinetics and crystallization of rod-shaped CaSO4·2H2O in aqueous solution.

In this study, a simple and efficient strategy is developed to synthesize rod-like CaSO4·2H2O (DH) crystals with tunable aspect ratio in aqueous solution using Cu2+ as modifier. The aspect ratio and length of the DH crystals are effectively reduced to 5.7 : 1 and about 35 µm in the presence of Cu2+, respectively. The interfacial tension value (γ) in the aqueous solution is improved significantly with the assistance of Cu2+, yet the nucleation rate (J) of the DH crystal is decreased sharply. The interfacial tension value (γ) in the aqueous solution is improved and the nucleation rate (J) of the DH crystal is drastically decreased due to the introduction of Cu2+, leading to the induction time of the DH crystallization being extended from 4 min to 25 min. The diversification of morphology for the DH crystals is incited by the changes of nucleation kinetics and Cu2+ incorporated into the crystal lattice, affecting the crystal growth habit, and finally controlling the growth of DH crystals in aqueous solution.

Controlled shape deformation of bilayer films with tough adhesion between nanocomposite hydrogels and polymer substrates.

Shape-shifting materials have received increasing attention owing to their promising applications in soft robotics, biomedical devices, actuators, morphing aircraft and so on. However, their practical applications are limited due to their weak mechanical strength, low interfacial adhesion and complex preparation method. In this paper, bilayer films were synthesized by in situ one-step forming soft and water-swellable nanocomposite hydrogels on the surface of the rigid and nonresponsive poly(ethylene terephthalate) (PET) film without any surface modification. The strong interfacial toughness between the hydrogel layer and the PET layer, the high swelling ability of the soft hydrogel layer, and the high strength of the rigid PET film endowed the bilayer film with excellent self-bending behaviour. The shape deformation of the bilayer films can be controlled by adjusting the geometry parameters of the bilayer film, such as the hydrogel thickness, the aspect ratio and the width of the bilayer film. Moreover, the bilayer film exhibited excellent reversible bidirectional self-bending behaviour. In addition, the mechanisms for driving the shape transformation were discussed. We believe this work will provide a promising and simple strategy to develop novel responsive materials with controlled shape deformation.