Douk Rae Lee

Transport properties of electrospun nylon 6 nonwoven mats

Abstract In this work, we evaluate the physical properties of nylon 6 nonwoven mats produced from solutions with formic acid. Nonwoven electrospun mats from various solutions with different concentration are examined regarding their morphology, pore size, surface area, and gas transport properties. Each nonwoven mat with average fiber diameters from 90 to 500 nm was prepared under controlled electrospinning process parameters. From the results, it was observed that the fiber diameter was strongly affected by the polymer concentration (polymer viscosity). In additional the results showed that the pore size, Brunauer–Emmett–Teller (BET) surface area, and gas transport property of electrospun nylon 6 nonwoven mats were affected by the fiber diameter.

Gelatin-coated magnetic iron oxide nanoparticles as carrier system: Drug loading and in vitro drug release study

Magnetic iron oxide nanoparticles (IOPs) were coated with gelatin A and B and drug-loading efficiency was investigated using doxorubicin (DXR) as a model drug to evaluate their potential as a carrier system for magnetic drug targeting. Drug loading to coated IOPs was done using adsorption as well as desolvation/cross-linking techniques to understand their role. Drug loading by adsorption technique was done by incubating mixture of coated IOPs and drug in various conditions of pH, DXR-to-coated IOPs ratio, gelatin types and IOPs amounts. Drug loading by desolvation/cross-linking technique was done by adding acetone and glutaraldehyde (GTA) to the mixture of coated IOPs and DXR. The results indicated involvement of electrostatic interaction during loading of DXR-to-coated IOPs. Compared to adsorption technique, desolvation/cross-linking technique improved the efficiency of drug loading regardless of type of gelatin used for the coating. The DXR-loaded particles showed pH responsive drug release leading to accelerate release of drug at pH 4 compared to pH 7.4.

Vanadium pentoxide nanofibers by electrospinning

New vanadate fibers with nano- to submicron diameter were prepared by electrospinning using vanadium sol and poly(vinylacetate) (PVAC) solutions followed by thermal treatment. The PVAC has been applied as structure directing template for the synthesis of vanadium oxide fibers. The fibers were characterized by SEM, AFM, XRD and IR spectra.

The photoluminescence properties of zinc oxide nanofibres prepared by electrospinning

The morphology and optical properties of zinc oxide fibres with diameters in the nanometre to micrometre range are reported. The PVA/zinc acetate organic/inorganic hybrid nanofibres were successfully prepared by electrospinning using polyvinyl alcohol (PVA) and zinc acetate. Pure zinc oxide fibres were obtained by high-temperature calcination of the hybrid fibres in air. The nanofibres were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffractometry (XRD) and Raman spectroscopy. The photoluminescence spectra under excitation at 325 nm showed an ultraviolet emission at 3.13 eV and a green emission at 2.21 eV. These nanofibres could be used as light emitting devices in nanoscale optoelectronic applications.

Preparation and morphology of niobium oxide fibres by electrospinning

Abstract Niobium oxide/poly(vinylacetate) composite nanofibres have been prepared by electrospinning method. Pure ceramic niobium oxide fibres were obtained by high temperature calcination of the organic–inorganic composite nanofibres. The materials have been characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and infra-red (IR) spectroscopy. It has been observed that both the morphology and the crystallinity of the fibres depend on the calcination temperature.

GeO2 fibers: Preparation, morphology and photoluminescence property

Nanomicron to submicron fibers of GeO(2) have been prepared using poly(vinyl acetate) and germanium dioxide sol by electrospinning followed by high temperature calcination. The morphology of the fibers have been studied by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. X-ray diffraction indicates that the fibers are single crystal with hexagonal alpha-phase quartz-like structure. At room temperature, the fibers show photoluminescence under excitation at 325 nm. The fibers may have potential applications in one-dimensional optoelectronic nanodevices.

Characterization of PVOH nonwoven mats prepared from Surfactant-Polymer system via electrospinning

The electrospinning process is a fascinating method to fabricate small nanosized fibers of diameter several hundred nanometers. Surfactant-polymer solutions were prepared by adding poly(vinyl alcohol) (PVOH) to distilled water with cationic, anionic, amphoteric, and non-ionic surfactants. Average diameter of the electrospun PVOH fibers prepared from PVOH solution was over 300 nm, and was decreased to 150 nm for the mixture of PVOH/ amphoteric surfactant. To explain the formation of ultrafine fiber, the characteristic properties in a mixture of PVOH/ surfactant such as surface tension, viscosity, and conductivity were determined. In this paper, the effect of interactions between polymers with different classes of surfactants on the morphological and mechanical properties of electrospun PVOH nonwoven mats was broadly investigated.

Effect of collector temperature on the porous structure of electrospun fibers

We report a new approach to fabricate electrospun polymer nonwoven mats with porous surface morphology by varying the collector temperature during electrospinning. Polymers such as poly(L-lactide) (PLLA), polystyrene (PS), and poly(vinyl acetate) (PVAc) ere dissolved in volatile solvents, namely methylene chloride (MC) and tetrahydrofuran (THF), and subjected to electrospinning. The temperature of the collector in the electrospinning device was varied by a heating system. The resulting nonwoven mats were characterized by using scanning electron microscopy (SEM), field emission SEM (FESEM), and atomic force microscopy (AFM). We observed that the surface morphology, porous structure, and the properties such as pore size, depth, shape, and distribution of the nonwoven mats were greatly influenced by the collector temperature.

Preparation of Electrospun Oxidized Cellulose Mats and Their in vitro Degradation Behavior

This paper investigated the effect of biodegradation behavior on the oxidation of cellulose nanofiber mats. The cellulose mats were produced through electrospinning. The diameter of an electrospun fiber varied from 90 to 240 nm depending on the electrospinning parameters, such as the solution concentration, needle diameter, and rotation speed of a grounded collector. Oxidized cellulose (OC) mats containing different carboxyl contents were prepared using NO2 as an oxidant. The total carboxyl content of the cellulose nanofiber mats obtained after oxidation for 20 h was 20.6%. The corresponding carboxyl content was important from a commercial point of view because OC containing 16–24% carboxyl content are used widely in the medical field as a form of powder or knitted fabric. Degradation tests of the OC mats were performed at 37°C in phosphate-buffered saline (pH 7.4). Microscopy techniques were introduced to study the morphological properties and the degradation behavior of the OC mats. Morphological changes of the mats were visualized using optical microscopy. Within 4 days of exposure to PBS, the weight loss of the OC mats was >90%.

Nonisothermal crystallization and melting behavior of the copolymer derived from p-dioxanone and poly(ethylene glycol)

Abstract Nonisothermal crystallization and melting behaviors of poly( p -dioxanone)(PPDO)-b-poly(ethylene glycol)(PEG) with mole ratios of 80:20 and 30:70, has been studied by differential scanning calorimeter using various cooling rates. Crystallization behavior of each crystallizable segments of the copolymer was compared with the corresponding segment of homopolymer. For a given composition, the crystallization process began at higher temperature when the slower scanning rates were used. The kinetics of the PPDO segments and the PEG segments in the copolymers under nonisothermal crystallization conditions were analyzed by Ozawa equation and also the crystallization results of the copolymer segments were compared with the corresponding homopolymers. The results showed that the Ozawa equation fails to describe the whole crystallization process of the copolymer segments along with PPDO homopolymer, but describes the crystallization behavior of the PEG homopolymer. Crystallization activation energy and absolute crystallinity values were estimated from the cooling scans (using Kissinger’s method) and fusion endotherms of the subsequent heating scans, respectively.