Dexin Chen,Yaoxin Li,Hongyuan He,Wei Li,Rong Zeng,Xiaojian Wang
Silver antibacterial composite coatings were prepared on additive manufactured Ti6Al4V substrates by merging anodic oxidation , molecular grafting, and spray deposition methods. The surface microstructure, composition, elemental characteristics, and antibacterial properties of the composite coatings were obtained. When the anodizing time was varied from 0.5 to 4 h, the results revealed that the average inner diameter of TiO 2 nanotubes (TNTs) increased from 19.9 nm to 78 nm and the average wall thickness decreased from 22.9 nm to 12.8 nm, concluding the optimized voltage of 40 V and anodizing time of 1 h. X-ray diffraction spectra depicted that the structure of TNTs transformed to the more stable anatase phase with a small amount of rutile phase after annealing. After molecule grafting, silanes are covalently bonding to the TNTs via amino groups and Si-O-Si networks. With the help of the covalent bonding between Ag and TNTs, the Ag + release has been slowed down significantly from 1.127 ppm to 0.17 ppm. Bare TNTs show a certain antibacterial effect with an antibacterial rate of 57.5% for E. coli and of 50.1% for S. aureus . When the spraying pass for Ag deposition is 10, the prepared AgNPs embedded coatings have significantly improved the antibacterial properties, as the antibacterial efficiencies are 100% for all these silane-modified TNTs surfaces.
The multi-molecular grafting interface becomes significant for the perfect structure construction of carbon fiber reinforced composite (CFRC), being built in this study between the epoxy-sized carbon fibers (CFs) and polyimide (PI) matrix via the multi-molecular coupling reactions among the epoxy sizing layer, hydroxyl-rich silicide nanomaterial (SiO 2 OH), and disulfide catalyst. They not only endowed the composite with multiple coupling interactions at the PI/CF interface but also promoted the surface-initiated radical curing reactions on both the sizing layer and the surface of SiO 2 OH. As a result, the SiO 2 OH nanofiller within the PI/CF composite constituted the composite interface with a nacre-like structure, exhibiting superior interfacial shear stability and excellent mechanical properties. The interfacial shear strength (IFSS) of the PI/CF composite reached 1.93 times the original thermally cured ones (value of 144.23 MPa), keeping higher flexural strength and modulus of 2000.1 MPa and 191.0 GPa. The nanofilling effect of SiO 2 OH components endowed the CFRC with structural integrity and mechanical failure mechanism based on the whole fracture of the composite rather than the delamination failure among the CF/matrix multilayers.
Amphiphilic supramolecular graft copolymers which can stabilize oil-in-water (o/w) emulsions and enable responsive demulsification were demonstrated in this study. Linear poly[(N,N-dimethylacrylmide)-stat-(3-acrylamidophenylboronic acid)] (PDMA-stat-PAPBA) copolymers with phenylboronic acid (PBA) groups and linear polystyrene homopolymers with cis-diol terminals (PS(OH)2) were synthesized by reversible addition–fragmentation chain transfer polymerization. By the homogenization of the biphasic mixtures of an alkaline water solution of PDMA-stat-PAPBA copolymer and a toluene solution of PS(OH)2 homopolymer, stable o/w emulsions could be generated, although neither PDMA-stat-PAPBA nor PS(OH)2 alone was able to stabilize the emulsion. It was verified that the dispersed oil droplets in the emulsions were stabilized by the amphiphilic PDMA-stat-PAPBA-g-PS supramolecular graft copolymers, which were formed in situ at the oil–water interface by the complexation between the lateral PBA groups of PDMA-stat-PAPBA and the diol terminals of PS(OH)2 during homogenization. These emulsions showed pH- and glucose-responsive demulsification because of the reversible B–O bonds between the PDMA-stat-PAPBA backbones and the PS side chains. The effects of polymer concentrations on emulsion formation were also investigated. The current study provides an alternative method for the facile preparation of responsive polymeric emulsifiers, which potentially may be extended to other polymer pairs containing PBA and cis-diol groups.
With the complexity of the working environment, pure epoxy resin can no longer meet the requirements, and the weak interfacial bonding between metal layer and epoxy-based composites limits its development. In this work, we propose a novel molecular grafting modification technique by using the active functional groups of polymers, which can apply to epoxy-based composites with various fillers to improve the adhesive strength of the interface between the metal film and matrix. 3D surface profile and surface wettability were used to characterize the effect of fillers on the surface of epoxy composites. Scanning electron microscope (SEM) and Raman spectroscopy were utilized to judge the interface failure modes of the composites. Peeling test and surface-enhanced Raman scattering (SERS) were conducted to examine how fillers affected adhesion. The results showed that silane grafting substantially improved the bonding between the epoxy-based composite matrix and the metal layer without the need for alkaline washing and palladium (Pd) activation steps on the substrate. The average adhesive strength can reach a maximum of 17.76 N/cm. The study also revealed the effect of filler size on the interfacial adhesive strength. The interfacial adhesive strength was increased by two dimensional lamellar materials, decreased by one-dimensional tubular materials, and remained unaffected by zero-dimensional spherical materials. This study may have positive implications for improving interfacial bonding between metal and polymer composite surfaces.
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