Enhancement Of Hydrophilicity Research Articles

Preparation and characterization of a novel hydrophilic PVDF/PVA UF membrane modified by carboxylated multiwalled carbon nanotubes

Polyvinylidene fluoride (PVDF)/polyvinyl alcohol (PVA) ultrafiltration (UF) membranes were prepared via a phase inversion method employing the modification of carboxylated multiwalled carbon nanotubes (MWCNTs-COOH). Various contents of MWCNTs-COOHs (0.00–0.15 wt%, weight of casting solution) were added into PVDF/PVA/dimethyl sulfoxide systems for the fabrication of the plate UF membrane. Fourier transform infrared spectroscopy spectra identified the successful introduction of carboxyl through the CO peak at 1730 cm−1. Scanning electron microscopy images exhibited the external surface and the asymmetric morphology with the appearance of a sponge-like inner structure. Atomic force microscopy analysis determined the roughness values and rougher topography. The hydrophilicity of the composite membrane containing 0.09 wt% of MWCNTs-COOHs improved the most. This sample has the highest pure water flux, approximately doubled (126.6 L·m−2·h−1) compared to the PVDF/PVA membrane (68.6 L·m−2·h−1), an enhanced bovine serum albumin flux recovery rate, showing an increase of 17%, and the best fouling resistance ability. Meanwhile, the porosity and dynamic contactangle also indicate the enhancement of membrane hydrophilicity. Dextran (DEX) 600k rejection reached 91.0%. Break strength, elongation at break, and Young's modulus also had improvements of 60%, 215.5%, and 56.7%, respectively, when the MWCNTs-COOH content was 0.12 wt%. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Effects of permeation enhancers on flufenamic acid delivery in Ex vivo human skin by confocal Raman microscopy

For effective topical delivery, a drug must cross the stratum corneum (SC) barrier into viable tissue. The use of permeation enhancers is a widespread approach for barrier modification. In the current study, flufenamic acid (FluA), a non-steroidal anti-inflammatory drug, is a model agent for investigating the influence of hydrophobic versus hydrophilic enhancers. In separate experiments, FluA in octanol or propylene glycol/ethanol (75/25) is applied to the SC for varying times followed by confocal Raman microscopic mapping of drug and enhancer penetration and spatial distribution. Deuterated versions of the enhancers permit us to spectroscopically distinguish the exogenous chemicals from the endogenous SC lipids without affecting penetration parameters. The FluA pathway is tracked by the CC stretching mode at ∼1618cm−1. Discrete, small inclusions of both enhancers are observed throughout the SC. High concentrations of FluA are co-localized with octanol domains which appear to provide a pathway to the viable epidermis for the drug. In contrast, FluA concentrates in the upper SC when using the hydrophilic agent and endogenous lipids appear unperturbed in regions outside the enhancer pockets. The ability to examine perturbations to endogenous ultrastructure and molecular structure in skin while tracking penetration pathways provides insight into delivery mechanisms.

Electrospun Carbon Nanofibers Decorated with Mn3O4 for Vanadium Redox Flow Battery

A flexible electrospun carbon nanofiber (CNF)-based electrode decorated with Mn3O4 is prepared starting from a solution containing polyacrilonitrile (PAN) mixed with manganese acetate (Mn(OAc)2). A thermal treatment at 270°C in air and a subsequent at 900°C in inert gas allow to obtain a flexible electrospun carbon nanofibers decorated with spinel manganese oxide (denoted as Mn3O4/CNF) characterized by suitable performance for vanadium redox flow battery (VRFB) application. Pristine electrospun carbon nanofibers CNF were prepared by using a similar method to compare the electrochemical data with respect to the decorated CNF. A homogeneous distribution of the metal oxides on the carbon nanofibers is showed by scanning electron microscopy (SEM) analysis. Cyclic voltammetry (CV) curves show a higher electrocatalytic activity toward the [VO]2+/[VO2]+ as well as the V2+/V3+ redox reactions with respect to the pristine electrospun CNF electrode, both in terms of peak to peak separation, DE[VO] 2+ /[VO 2 ] + = 0,15 V vs. 0,28 V, and Ipa/Ipc[VO] 2+ /[VO 2 ] + ratio, 1,48 vs 1,58, respectively. The improved performance is attributed to the hydrophilicity enhancement due to the oxygen groups availability that favour the surface mechanism process on the carbon nanofibers decorated with metal oxide nanoparticles.

Unusual Morphologies of Poly(vinyl alcohol) Thin Films Adsorbed on Poly(dimethylsiloxane) Substrates.

Adsorption of poly(vinyl alcohol) (PVOH), 99% and 88% hydrolyzed poly(vinyl acetate), to poly(dimethylsiloxane) (PDMS) substrates was studied. The substrates were prepared by covalently attaching linear PDMS polymers of 2, 9, 17, 49, and 116 kDa onto silicon wafers. As the PDMS molecular weight/thickness increases, the adsorbed PVOH thin films progressively transition from continuous to discontinuous morphologies, including honeycomb and fractal/droplet. The structures are the result of thin film dewetting that occurs upon exposure to air. The PVOH film thickness does not vary significantly on these PDMS substrates, implicating the PDMS thickness as the cause for the morphology differences. The adsorbed PVOH thin films are less stable and have a stronger tendency to dewet on thicker, more liquid-like PDMS layers. When PVOH(99%) and PVOH(88%) thin films are compared, fractal and droplet morphologies are observed on high molecular weight PDMS substrates, respectively. The formation of the unique fractal features in the PVOH(99%) thin films as well as other crystalline and semicrystalline thin films is most likely driven by crystallization during the dehydration process in a diffusion-limited aggregation fashion. The only significant enhancement in hydrophilicity via PVOH adsorption was obtained on PDMS(2k), which is completely covered with a PVOH thin film. To mimic the lower receding contact angle and less liquid-like character of the PDMS(2k) substrate, light plasma treatment of the higher molecular weight PDMS substrates was carried out. On the treated PDMS substrates, the adsorbed PVOH thin films are in the more continuous honeycomb morphology, giving rise to significantly enhanced wettability. Furthermore, hydrophobic recovery of the hydrophilized PDMS substrates was not observed during a 1 week period. Thus, light plasma oxidation and subsequent PVOH adsorption can be utilized as a means to effectively hydrophilize conventional PDMS substrates. This study illustrates that the stability and morphology of adsorbed polymer thin films depend on polymer crystallinity as well as substrate physical properties.

The Effect of Surface Modification of Aligned Poly-L-Lactic Acid Electrospun Fibers on Fiber Degradation and Neurite Extension.

The surface of aligned, electrospun poly-L-lactic acid (PLLA) fibers was chemically modified to determine if surface chemistry and hydrophilicity could improve neurite extension from chick dorsal root ganglia. Specifically, diethylenetriamine (DTA, for amine functionalization), 2-(2-aminoethoxy)ethanol (AEO, for alcohol functionalization), or GRGDS (cell adhesion peptide) were covalently attached to the surface of electrospun fibers. Water contact angle measurements revealed that surface modification of electrospun fibers significantly improved fiber hydrophilicity compared to unmodified fibers (p < 0.05). Scanning electron microscopy (SEM) of fibers revealed that surface modification changed fiber topography modestly, with DTA modified fibers displaying the roughest surface structure. Degradation of chemically modified fibers revealed no change in fiber diameter in any group over a period of seven days. Unexpectedly, neurites from chick DRG were longest on fibers without surface modification (1651 ± 488 μm) and fibers containing GRGDS (1560 ± 107 μm). Fibers modified with oxygen plasma (1240 ± 143 μm) or DTA (1118 ± 82 μm) produced shorter neurites than the GRGDS or unmodified fibers, but were not statistically shorter than unmodified and GRGDS modified fibers. Fibers modified with AEO (844 ± 151 μm) were significantly shorter than unmodified and GRGDS modified fibers (p<0.05). Based on these results, we conclude that fiber hydrophilic enhancement alone on electrospun PLLA fibers does not enhance neurite outgrowth. Further work must be conducted to better understand why neurite extension was not improved on more hydrophilic fibers, but the results presented here do not recommend hydrophilic surface modification for the purpose of improving neurite extension unless a bioactive ligand is used.

Investigation of physical and biological properties of polypyrrole nanotubes–chitosan nanocomposites

Polypyrrole nanotubes–chitosan (PPy-NTs:chitosan) nanocomposite films have been synthesized with varying concentration of polypyrrole nanotubes (PPy-NTs) and their physical and biological properties have been investigated. Scanning electron microscopy (SEM) micrographs exhibit the increase in surface roughness of the nanocomposite films with increasing concentration of PPy-NTs. Enhancement in hydrophilicity of the nanocomposite films has been observed after surface functionalization with glutaraldehyde which is attributed to increase in surface energy due to the incorporation of polar groups on the films surface. The increasing amount of PPy-NTs in the nanocomposite leads to an increase in haemolysis activity, while the treatment with glutaraldehyde results in the decrease in haemolysis activity giving rise to higher biocompatibility. Urease immobilization in glutaraldehyde treated films exhibits higher enzymatic activity as compared to that of the untreated films, which is attributed to the enhancement in hydrophilicity and biocompatibility of the PPy-NTs:chitosan nanocomposites after functionalization with glutaraldehyde.

Effect of Post-Treatment Techniques on Corrosion and Wettability of Hydroxyapatite-Coated Co–Cr–Mo Alloy

This study is a comparison between the effect of sintering and alkaline post-treatment techniques on calcium phosphate-coated Co–Cr–Mo alloy in terms of electrochemical corrosion behavior and wettability. The Co–Cr–Mo substrates were electrophoretically coated by calcium phosphate in a solution of Ca(NO3) · 4H2O and NH4H2PO4. The sintering and alkaline post-treatment techniques were then conducted to convert an as-deposited dicalcium phosphate dihydrate phase to crystalline hydroxyapatite (HA). The coated layers were characterized in terms of phase, crystallinity and composition using X-ray diffraction, Fourier transform infrared spectroscopy and energy-dispersive spectroscopy. In addition, morphology and thickness of coated layers were evaluated using a scanning electron microscope. The results indicate HA-coated samples with a sintering post-treatment technique exhibit more improvement in corrosion parameters, such as corrosion potential (Ecorr) and corrosion current density (Icorr), but lower enhancement in hydrophilicity. However, the HA-coated samples with an alkaline post-treatment technique reveal higher hydrophilicity with lower improvement in corrosion resistance.

Surface roughness and hydrophilicity enhancement of polyolefin-based membranes by three kinds of plasma methods

The introduction of antibacterial property, conductivity, wettability and antithrombogenicity into polyolefin-based membranes has evoked much attention, which can be achieved by coating hydrophilic polymers. Therefore, it is necessary to modify the roughness and hydrophilicity of polyolefin-based membranes to enhance the coating ability. In this paper, three kinds of plasma methods, including inductively coupled (ICP) plasma, radio frequency low pressure (RFP) plasma and atmospheric dielectric barrier discharge (DBD) plasma, were used to modify the surface of the polyethylene (PE), polypropylene (PP) and polyester-polypropylene (PET–PP) membranes. The surface roughness of the plasma-modified PE, PP and PET–PP films was investigated by scanning electron microscopy (SEM) and atomic force microscope (AFM). The polar functional groups of films were observed by energy dispersive spectrometer (EDX) and X-ray photoelectron spectroscopy (XPS). Besides, the hydrophilicity of the plasma-modified PE, PP and PET–PP films was evaluated by water contact angle measurement. It was found that the surface roughness and hydrophilicity of plasma-modified PE, PP and PET–PP films increased with the generation of oxygen-containing functional groups (i.e. C―O, and CO). The PET–PP membranes were treated by RFP plasma at different processing powers and times. These results indicated that plasma is an effective way to modify films, and the treatment time and power of plasma had a certain accumulation effect on the membranes' hydrophilicity. As for the roughness and hydrophilicity, the DBD plasma modifies the PE film, which is the optimum way to get the ideal roughness and hydrophilicity. Copyright © 2015 John Wiley & Sons, Ltd.

Remarkable permeability enhancement of polyethersulfone (PES) ultrafiltration membrane by blending cobalt oxide/graphene oxide nanocomposites

The process scheme of preparation of hybrid ultrafiltration membranes.

Enhancement of chondrocyte proliferation, distribution, and functions within polycaprolactone scaffolds by surface treatments.

Enhancement of porcine chondrocyte growth, distribution and functions within polycaprolactone (PCL) scaffolds was attempted using alkaline hydrolysis and oxygen plasma treatment. The hydrolysis of PCL was performed either before or after scaffold fabrication in the preparations of pre-hydrolyzed PCL (pre-HPCL) or post-HPCL scaffolds, respectively. The PCL, pre-HPCL, and post-HPCL scaffolds were subsequently plasma-treated to yield plasma-treated PCL, plasma-treated pre-HPCL, and plasma-treated post-HPCL scaffolds, respectively. All scaffolds were comparatively characterized, in terms of surface morphology, hydrophilicity, and atomic composition using scanning electron microscopy, contact angle measurement and X-ray photoelectron spectroscopy, respectively. The interactions of chondrocytes with individual scaffolds were assessed, in terms of cartilage-gene expression and cartilaginous matrix production using reverse transcription polymerase chain reaction analysis and glycosaminoglycans (GAGs) assay, respectively. The cell infiltration and cartilaginous matrix distribution were investigated by histological and immunofluorescence analysis. The results revealed that the plasma treatment exhibited a more prominent effect on the enhancement of surface roughness and hydrophilicity of the scaffolds than the alkaline hydrolysis. The scaffolds subjected to both surface treatments stimulated the cells to secret more GAGs and type II collagen. The sequence of hydrolysis of PCL also evidently played a crucial role in the hydrophilicity of the materials and the cartilage-gene expression and cartilaginous matrix production of the cultured chondrocytes. The hydrolysis of PCL prior to the fabrication, followed by the oxygen plasma treatment of the resulting fabricated scaffold, yielded plasma-treated pre-HPCL scaffold with homogeneous hydrophilic characteristics all over the material. Consequently, the cells could proliferate well, infiltrate most deeply and ultimately produce the highest amounts of the cartilage-specific substances throughout this scaffold.

The effect of UV irradiation on PSf/TiO2 mixed matrix membrane for chromium rejection

The study investigated a novel approach for surface modification of membranes and sustainable water recovery from chromium contaminated water by employing a lab scale dead-end cell filtration unit. Various PSf/TiO2 composite membranes prepared with different concentrations of TiO2 nanoparticles were exposed to UV radiations for surface modification. On exposure to UV light, TiO2 nanoparticles emit electrons and create a surface roughness with a charge on the membranes which resulted in enhanced chromium rejection as well as flux. The surface modification has been analyzed by AFM and SEM (surface and cross sectional) images. The structural modification was investigated by ATR-IR and UV–Visible spectroscopy. The expected enhancement in hydrophilicity was studied by water uptake and contact angle measurements. The analysis of water flux and chromium rejection performed in a dead end filtration unit revealed a high water flux and 100% chromium rejection with 2wt.% of TiO2 composite membrane in acidic pH. The pH of feed plays an important role in chromium rejection. The rejection of chromium decreases with an increase in feed concentration due to the variation in ion distribution. The effect of interference of other metals in chromium rejection is investigated. The overall work not only demonstrates the positive effects of surface modification, but also effective removal of hazardous chromium.

The Research of Hydrophilic Modification of PVC/PES Blended Membrane by the Additive of CA

In order to improve the performance of Poly(vinyl chloride)(PVC)/ polyethersulfone (PES) blended membranes, cellulose acetate (CA) was used as a hydrophilic enhancer to blend with PVC and PES for membrane preparation by phase inversion method. In this study, the results of equilibrium water content (EWC), contact angle and X-ray photoelectron spectroscopy (XPS) confirmed the addition of CA could effectively improve the hydrophilicity of PVC/PES blended membrane. It was also found that water flux of PVC/PES/CA blended membranes increased with the increase of CA concentration.

Performance of PVA/NaA Mixed Matrix Membrane for Removal of Water from Ethylene Glycol Solutions by Pervaporation

A mixed matrix membrane with superior performance was prepared by incorporating zeolite NaA particles in polyvinyl alcohol (PVA) for dehydration of ethylene glycol (EG)-water mixtures. The zeolite NaA, with its favorable interaction with the polymer phase, is responsible for improving the pervaporation (PV) dehydration of EG-water mixtures in terms of separation factor, permeation flux, and PV separation index (PSI). This improvement is due to hydrophilicity enhancement, and molecular sieving action and selective adsorption of zeolite. It was found out that membrane with 5 wt.% loading of particles shows the highest separation factor of 1520 with a permeation flux of 2.4 kg/m2h at 70°C for a feed mixture of 20 wt.% of water in EG.

Surface modification of polyethersulfone ultrafiltration membranes by corona plasma-assisted coating TiO2 nanoparticles

In this work, the surface of polyethersulfone (PES) ultrafiltration membranes was modified by corona air plasma and coating TiO2 nanoparticles in order to improve the separation and antifouling properties. For this purpose, the TiO2 nanoparticles which were synthesized in a rutile phase by a microwave hydrothermal method, were coated on the surface of the corona plasma treated PES membranes which were prepared via the non-solvent-induced phase inversion method. The effects of corona treatment conditions on the morphology, surface properties and separation performance of the modified membranes were studied. The fabricated membranes were characterized by FTIR-ATR, SEM, AFM and contact angle analysis. The fouling resistance and separation performance of the membranes were also evaluated by the UF permeation tests of pure water and oil in water emulsions. The experimental results showed that the corona treatment and coating TiO2 nanoparticles led to a significant enhancement of the surface hydrophilicity, improvement of the antifouling properties and permeation fluxes for all modified membranes without significant changes in cross sectional morphology of the membranes. The modified membranes had a lower fouling tendency and long term flux stability in comparison to the untreated PES membranes. Furthermore, an increase in the corona input power and treatment time resulted in higher hydrophilicity of the membrane surface as well as much more deposition of TiO2 nanoparticles on the membrane.

Enhancement of hydrophilicity of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane using various alcohols as nonsolvent additives

Flat sheet asymmetric polymeric membranes were prepared from homogeneous solution of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) by phase inversion method using N-methyl-2-pyrrolidone (NMP) as solvent and PEG 6000 as pore forming agent. The effects of addition of different alcohols viz. methanol, ethanol, n-propanol, n-butanol and various quantity of methanol in the casting solution on membrane properties were investigated. The morphology and structure of resulting membranes were observed by field emission scanning electron microscope (FESEM). The permeation performances of the membranes were evaluated in terms of pure water flux (PWF), hydraulic permeability and solute rejection capacity. Extent of membrane hydrophilicity was evaluated in terms of porosity, equilibrium water content (EWC) and water contact angle. Solution of bovine serum albumin (BSA) of molecular weight 68,000Da was used to study the permeation performance of prepared membranes using a batch cell of 350mL capacity. Membranes with 5wt.% of methanol showed highest PWF and smallest water contact angle, while membranes containing different alcohols have almost same PWF.

Surface Modification of Polypropylene Blood Oxygenator Membrane by Poly Ethylene Glycol Grafting

Blood oxygenators play key role in Extra Corporeal Membrane Oxygenator (ECMO) system using for patients with acute respiratory problems, immature fetal and also in open heart surgery. Interaction between blood and blood oxygenator polymeric membrane surface lead to fouling phenomena which have negative effect on performance of this important medical device. A modification comprising surface activation, PEG immersing and PEG graft polymerization carried out to provide acceptable blood oxygenator performance, blood compatibility and reduction in heparin consumption at the same time. Modified membranes characterized by FTIR, contact angle measurements and Atomic Force Microscopy (AFM) analyses. Blood compatibility of modified surface was also detected by SEM images. Results clearly indicate that modifying membranes by PEG is an effective way for anti-fouling properties. Water contact angel reduction from 110ْ to 72ْ shows hydrophilicity enhancement, roughness increasing from 15 to 20 and blood compatibility improvement was investigated by SEM and AFM analysis results respectively.

Effect of PEGylated chitosan on plasma etched PET fabrics surface properties

ABSTRACTIn this work, PEGylated chitosan derivatives were prepared and used to modified poly(ethylene terephthalate) (PET) fabrics. PET fabrics surface were etched by oxygen plasma before different concentrations PEGylated chitosan derivatives solution treatment. The effects of oxygen plasma and PEGylated chitosan derivatives on the surface properties of PET fabrics are investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Surface wettability was monitored by water contact angle measurement and moisture regains. The results showed that the occurrence of oxygen‐containing functional groups (i.e., CO, CO, and OH) of the plasma‐treated PET and the surface coarseness increased from those of the untreated one. There was a layer film formed on the surface of PET fabrics after PEGylated chitosan modification. The combination treatment of oxygen plasma with PEGylated chitosans lightly lowered the breaking strength and elongation of PET fabric. That moisture regains increased and the contact angle decreased implied the hydrophilicity enhancement for the PET fabrics. In addition, dyeing property of PEGylated chitosan derivative modified PET was improved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39693.

Enhanced pervaporation dehydration performance of ultrathin hybrid membrane by incorporating bioinspired multifunctional modifier and TiCl4 into chitosan

3-(3,4-Dihydroxyphenyl)propionic acid (DHPPA) was introduced as a bioinspired multifunctional modifier to mediate the in situ sol–gel reaction of TiCl4 within chitosan (CS) matrix through metal–organic coordination. Ultrathin, robust chitosan–titania hybrid membranes were obtained in a facile way. The morphology, chemical and physical structures, as well as the hydrophilicity and thermal stability of hybrid membranes were extensively characterized. An ethanol/water mixture was chosen as a model system to evaluate the swelling resistance property and pervaporation dehydration performance of the hybrid membranes. The simultaneous enhancement of hydrophilicity and swelling resistance was achieved due to the presence of numerous carboxyl groups and the stable hybrid structure. The multiple interfacial interactions between polymeric and inorganic phases, as well as the steric effect of the bioinspired modifier, led to significant pervaporation performance enhancement of CS membrane. When the mass ratio of TiCl4 to CS was 14wt%, the hybrid membrane exhibited the optimal pervaporation performance with a permeation flux of 1403g/(m2h) and a separation factor of 730 for 90wt% ethanol aqueous solution at 350K. The operation stability was also testified in long-term pervaporation separation test.

Surface modification of polypropylene fiber for hydrophilicity enhancement aided by DBD plasma

Low-wetting low-hydrophilicity polipropylene fiber has been treated by means of non-thermal dielectric barrier discharge plasma. The fiber has been characterized before and after the treatment by scanning electron microscopy (SEM), X-ray diffraction, atomic force microscopy (AFM) and industrial tests of submersion in water. The cold plasma was generated in a helium–air mixture at a 2kHz frequency and 12–18kV potential. The treatment periods ranged from 1min up to 3min. The results present an increase in the oxygen content which rose from 2.5% to 4.8%. SEM analysis reveals a surface change of the fiber with the formation of nodules, which is confirmed by AFM. Water submersion experiments show an enhancement of the hydrophilic capability of the samples.

Metal microelectrode nanostructuring using nanosphere lithography and photolithography with optimization of the fabrication process

Nanostructured metal microelectrodes were fabricated using a combination of nanosphere lithography, conventional photolithography and physical vapour deposition techniques. Specifically, Pt and Ag microelectrodes, patterned by hexagonal nanotriangular Ag arrays were prepared, introducing Ag and bimetallic Ag on Pt microelectrode nanostructured systems. Enhancement of surface hydrophilicity was achieved via electric discharge on the electrode surface or via physicochemical interactions (dipping the substrates into NaOH solution). Following removal of the nanospheres, uniform hexagonal arrays of metal nanostructures were revealed and characterized by scanning electron and atomic force microscopy analysis. Parameters relevant to the self-assembly of the colloid arrays and the fabrication methodology employed is discussed with respect to process optimization.