Carbonized electrospun polyvinylpyrrolidone/metal hybrid nanofiber composites for electrochemical applications

Electrospinning is a very versatile and efficient method of fabricating nanofibers with the desired properties. Polyvinylpyrrolidone (PVP) in ethanol solution was electrospun into nanofibers and used as a precursor for the preparation of carbon nanofibers. Cobalt chloride was also incorporated with PVP nanofibers to produce carbon nanofiber composites with enhanced electrical conductivity and electrochemical properties. The surface morphology and physical properties of the electrospun nanofibers, carbonized nanofibers, and their composites were observed by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. The electrochemical behavior of the carbon nanofiber composites was studied by drop‐casting on a working surface of the screen‐printed carbon electrode and examined by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that carbon nanofiber composites were decorated with cobalt nanoparticles and enhanced the charge‐transfer efficiency on the electrode surface. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45639.     

Effects of crosslinking ratio,model drugs,and electric field strength on electrically controlled release for alginate-based hydrogel

The drug release characteristics of calcium alginate hydrogels, (Ca-Alg), under an electric field assisted transdermal drug delivery system were systematically investigated. The Ca-Alg hydrogels were prepared by the solution-casting using CaCl₂ as a crosslinking agent. The diffusion coefficients and the release mechanism of the anionic model drugs, benzoic acid and tannic acid, and a cationic model drug, folic acid on the Ca-Alg hydrogels were determined and investigated using a modified Franz-Diffusion cell in an MES buffer solution of pH 5.5, at a temperature of 37°C, for 48 h. The influences of the crosslinking ratio, —the mole of the crosslinking agent to the mole of the alginate monomer—mesh size, model drug size, drug charge, electric field strength, and electrode polarity were systematically studied. The drug diffusion coefficient decreased with an increasing crosslinking ratio and drug size for all of the model drugs. The drug diffusion coefficient is precisely controlled by an applied electric field and the electrode polarity depending on the drug charge, suitable for a tailor-made transdermal drug delivery system.     

Hybrid transdermal drug delivery patch made from poly(p‐phenylene vinylene)/natural rubber latex and controlled by an electric field

A flexible, natural rubber (NR) patch was developed for electrically controllable transdermal drug delivery. NR latex was crosslinked at various crosslinking ratios under the UV curing method. Ibuprofen (Ibu) was the model drug and was used as the dopant for poly(p‐phenylene vinylene) (PPV) acting as the drug encapsulating host. For the pristine Ibu‐loaded NR patch, the amount of Ibu permeation increased with decreasing crosslink density and increasing electrical potential. For the Ibu‐doped PPV/NR patch, the amount of Ibu release?permeation also increased with increasing electrical potential and was higher than that of the pristine NR matrices. Without an applied electric field, the drug remained attached to the PPV during an initial period of 6 h. Under an applied electric field, the oxidation state of the conductive polymer was altered, the iontophoretic effect, pore formation in the NR matrix, expansion of the pore size in hair follicles and PPV chain expansion combined to increase the Ibu release?permeation amount. Thus, the flexible PPV/NR transdermal drug delivery patch was demonstrated to be effective in drug release?permeation based on the strength of the electrical potential, the crosslinking density and the presence of PPV as the encapsulation host. © 2018 Society of Chemical Industry     

Electric field induced stress moduli of polythiophene/polyisoprene suspensions: Effects of particle conductivity and concentration

Electrorheological properties of polythiophene/polyisoprene suspensions were investigated in the oscillatory shear mode under electric field varying from 0 to 2 kV/mm. Poly(3‐thiophene acetic acid) particles were synthesized via an oxidative polymerization and doped with perchloric acid in order to vary electrical conductivity. ER responses can be enhanced with increasing electric field strength, particle electrical conductivity, and particle concentration. The storage modulus (G′) increases dramatically by 3 and 4 orders of magnitude, with the variations of particle conductivity and particle concentration as the electric field strength is increased from 0 to 2 kV/mm The results can be interpreted in terms of the difference in the polarizability between the particles and the matrix, and the particle agglomeration existing at high particle electrical conductivity and high particle concentration. The suspensions exhibit the transitions from the fluid‐like behavior to the solid‐like behavior at the critical electric field strengths. In particular, the sol‐to‐gel transitions occur at lower electrical field strengths with higher particle electrical conductivity and at higher particle concentration.