Adsorption of poly(vinyl formamide-co-vinyl amine) (PVFA-co-PVAm) polymers on zinc, zinc oxide, iron, and iron oxide surfaces

Polymer-Assisted 3D Printing of Inductor Cores

Poly(glycerol monomethacrylate) (PGMA) prepared by reversible addition-fragmentation chain transfer polymerization was investigated as an additive for high-loading iron oxide nanoparticle (IOP) 3D printable inks. The effect of adjusting the molar mass and loading of PGMA on the rheology of IOP suspensions was investigated, and an optimized ink formulation containing 70% w/w IOPs and 0.25% w/w PGMA98 at pH 10 was developed. This ink was successfully 3D printed onto various substrates and into several structures, including rectangles, high aspect ratio cylinders, letters, spiral- and comb-shaped structures, and thin- and thick-walled toroids. The effect of sintering on the mechanical properties of printed artifacts was investigated via four-point flexural and compressive testing, with higher sintering temperatures resulting in improved mechanical properties due to changes in the particle size and microstructure. The printed toroids were fabricated into inductors, and their electrical performance was assessed via impedance spectroscopy at a working frequency range of 0.001-13 MHz. There was a clear trade-off between electrical properties and sintering temperature due to a phase change between γ-Fe2O3 and α-Fe2O3 upon heating. Nevertheless, the optimized devices had a Q factor of ∼40 at 10 MHz, representing a superior performance compared to that of other inductors with iron oxide cores previously reported. Thus, this report represents a significant step toward the development of low-cost, fully aqueous, high loading, and 3D printable ceramic inks for high-performance inductors and functional devices.

Sustainable decontamination of heavy metal in wastewater and soil with novel rectangular wave asymmetrical alternative current electrochemistry

A new concept of removal and recovery of heavy metals and simultaneous regeneration and reuse of ethylenediamine-tetraacetic acid (EDTA) in soil washing effluent containing metal-EDTA complexes is proposed, which is used to remediate heavy metal contaminated soil. To achieve this goal, soil washing approach coupled with rectangular wave asymmetrical alternative current electrochemistry (RW-ACE) equipped with amidoxime-functionalized electrodes (Ami-CF) is employed. With high hydrophilicity and strong binding affinity, Ami-CF could specifically compete for heavy metals over EDTA under electric field. RW-ACE system is found successfully to achieve the non-destructive decomplexation of heavy metal-EDTA, and then regenerate EDTA for highly recycling, which saves as high as 98.9 % EDTA consumption compared with conventional washing method. Moreover, more than 90% of heavy metals are recovered and deposited on the electrode with a majority of them existed as zero-valence state as evidenced by XPS. The RW-ACE method is universal for various heavy metals such as Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ in an authentic contaminated soil, and the loss of soil nutrient is very limited. Along with long-term assessment and operation cost estimation, the RW-ACE method is a sustainable remediation approach for the heavy metal polluted wastewater and soils, and easily scaled up for field practice.

Interactions of bioactive molecules with thin dendritic glycopolymer layers

The authors report on highly swellable, stable layers of spherical dendritic glycopolymers, composed of hyperbranched poly(ethylene imine) (PEI) as core and two different maltose shells (A = dense shell and B = open shell). These glycopolymers are cross-linked and attached with poly(ethylene-alt-maleic anhydride) (PEMA) or citric acid on SiO_x substrates. The swelling and adsorption of biomolecules were analyzed by spectroscopic ellipsometry and quartz crystal microbalance with dissipation. The swelling degree and complexation with the drug molecule adenosine triphosphate (ATP) were found to be up to 10 times higher for dendritic glycopolymer layers cross-linked with PEMA than for layers cross-linked with citric acid. ATP complexation by electrostatic interaction with the PEI cores was confirmed by x-ray photoelectron spectroscopy analysis. Complexation led to partial collapsing, stiffening, and increase of polymer layer viscosity of the PEMA cross-linked layers. From modeling of ellipsometric data, it was deduced that ATP complexation preferably takes place at the polymer layer-solution interface. The size effect of the adsorbates was investigated by comparing ATP complexation with the adsorption of larger vitamin B12 and human serum albumin (HSA) protein. PEI-Mal A cross-linked with PEMA was found to be resistant toward B12 and HSA adsorption due to the diffusion barrier of the polymer layer. Thus, the authors present potentially biocompatible polymer surfaces for drug loading and their surface supported release.

Single Additive Enables 3D Printing of Highly Loaded Iron Oxide Suspensions

A single additive, a grafted copolymer, is designed to ensure the stability of suspensions of highly loaded iron oxide nanoparticles (IOPs) and to facilitate three-dimensional (3D) printing of these suspensions in the filament form. This poly (ethylene glycol)-grafted copolymer of N-[3(dimethylamino)propyl]methacrylamide and acrylic acid harnesses both electrostatic and steric repulsion to realize an optimum formulation for 3D printing. When used at 1.15 wt % (by the weight of IOPs), the suspension attains ∼81 wt % solid loading-96% of the theoretical limit as calculated by the Krieger-Dougherty equation. Rectangular, thick-walled toroidal, and thin-walled toroidal magnetic cores and a porous lattice structure are fabricated to demonstrate the utilization of this suspension as an ink for 3D printing. The electrical and magnetic properties of the magnetic cores are characterized through impedance spectroscopy (IS) and vibrating sample magnetometry (VSM), respectively. The IS indicates the possibility of utilizing wire-wound 3D printed cores as the inductive coils. The VSM verifies that the magnetic properties of IOPs before and after the ink formulation are kept almost unchanged because of the low dosage of the additive. This particle-targeted approach for the formulation of 3D printing inks allows embodiment of a fully aqueous system with utmost target material content.

Adsorption of poly(vinylformamide-co-vinylamine) polymers (PVFA-co-PVAm) on copper

The adsorption of poly(vinylformamide) (PVFA) and its derivative statistical copolymer poly(vinyl-formamide-co-vinylamine) (PVFA-co-PVAm) on metallic copper and copper oxide particles as well as planar copper surfaces was studied as a function of the degree of hydrolysis of PVFA, the pH, and the polymer concentration in solution. The chemical composition and molecular structure of the PVFA-co-PVAm layers were investigated by surface-sensitive spectroscopic methods such as XPS, DRIFT spectroscopy, and ellipsometry. The findings allowed us to explain the adsorption mechanisms and the forces driving the PVFA-co-PVAm adsorption. It was shown that PVFA-co-PVAm layers thicker than 30 nm are able to protect the planar copper surface against corrosive attack.