Increase In PVA Concentration Research Articles

Nanoclay Reinforced Ternary Blends Based on Biodegradable Polymers for Drug Delivery Application.

In this study, ternary blends based on chitosan, polyvinyl alcohol, and polyethylene glycol reinforced with organically modified montmorillonite (nanoclay) clay were synthesized. These ternary blends were evaluated as transdermal drug delivery patches using tramadol as a model drug. The FTIR study showed interaction among important functional groups and compatibility among the mixing components. Among drug-loaded formulations, composite MA12 shows maximum thermal stability with 27.9% weight residue at 540°C. The prepared formulations exhibited crystalline nature as observed by XRD analysis. SEM studies revealed that there are no gaps and cracks in prepared films and nanoclay was found dispersed in the formulations. The swelling ratio was higher in pH 1.2 as compared to pH 4.5 and pH 6.8 buffers, and there was an increase in swelling with an increase in PVA concentration. Moreover, the drug release test performed in phosphate buffer pH 6.8 showed that tramadol release from nanocomposite films increases with an increase in PEG concentration. Permeation studies indicated that the rate of permeation increased with a decrease in PVA concentration. The permeation rate was found to be higher for samples without nanoclay. The overall results suggest nanocomposite films as excellent candidates for transdermal drug delivery application.

Effects of binary solvent mixtures on the electrospinning behavior of poly (vinyl alcohol)

Different concentrations of PVA solutions were prepared and electrospun from water, ethanol-water and acetic acid-water binary solvent mixtures to study the effects of binary solvent mixtures. The solubility and spinnability of the prepared PVA solutions were discussed using Teas graph. The viscosity of the PVA solutions increased with the increase of PVA concentration. After electrospinning, fibers with an average diameter in the range of 70–300 nm were observed for the fibers spun from acetic acid-water binary solvent mixtures and in the range of 500–1000 nm for the fibers spun from ethanol-water binary solvent mixtures. Circular fibers at lower PVA concentration and flat fibers at higher PVA concentration were observed for the fibers spun from acetic acid-water solutions. Flat fibers were found in case of all the fibers irrespective of PVA concentrations spun from of ethanol-water binary solvent mixtures. Fiber diameters showed an inverse relationship with respect to the electrical conductivity of the solutions, regardless of the solvents. Fiber mats spun from acetic acid-water binary solvent mixtures exhibited nearly double the tensile strength than those of ethanol-water binary solvent mixtures. Differential scanning calorimetry (DSC) analysis of the electrospun fiber mats showed no effect of solvents on thermal properties.

Rheological behavior of starch–poly(vinyl alcohol)–TiO2 nanofluids and their main and interactive effects

ABSTRACTIn this study, an investigation of the rheological behavior of starch/poly(vinyl alcohol) (PVA)/titanium oxide (TiO2) nanofluids was performed. It revealed that the rheological behavior of starch suspensions displays a particular change due to the presence of PVA and TiO2. All examined fluids demonstrated non‐Newtonian behavior and followed the Power law model. The main and interacting effects of starch, PVA, and TiO2 nanoparticles concentrations were studied using the analysis of variance. The results indicated that the flow behavior index (n), as well as the consistency index (K) of suspensions, is influenced by the PVA and TiO2 contents. The flow behavior index (n) decreased and consistency index (K) increased by an increase in PVA concentration. A reverse trend is observed by the addition of TiO2 nanoparticles to starch and PVA blend suspensions. The difference in rheological behaviors was ascribed to the presence of binary and triplet interactions between starch, PVA, and TiO2 nanoparticles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44062.

Properties of as-prepared and freeze-dried hydrogels made from poly(vinyl alcohol) and cellulose nanocrystals using freeze-thaw technique

Poly(vinyl alcohol), PVA hydrogels are potential materials for biomedical and biotechnogical applications. However, their low mechanical properties restrict their use. In this study, the effect of PVA concentration, addition of nanocrystalline cellulose, CNC, number of freeze-thaw cycles and freeze-drying stage on properties of resulting hydrogels were investigated. The results showed that increase in PVA concentration and the addition of CNC improved the compressive properties of the hydrogels. Overall, increase in number of freeze-thaw cycles from 3 to 5 did not show any improvements in properties of hydrogels. Concentration of PVA had great effect on morphology of freeze-dried hydrogels. The CNC reduced crystallinity of PVA/CNC hydrogels as compared to PVA hydrogels. Rehydrated PVA and PVA/CNC hydrogels had higher compressive characteristics than their as-prepared analogues. In general, an improvement of compressive properties of hydrogels was achieved via reduction of their water content. In case of 5% PVA hydrogel, an addition of CNC was found to be beneficial because it increased degree of swelling and water content on rehydration.

Structural and optical properties of PVA doped zinc sulphide thin films

Abstract Zinc sulphide (ZnS) nanostructured thin films have been prepared using CBD method on glass substrate at room temperature under three different concentrations of PVA. The structural and optical properties of the films have been studied. The XRD pattern suggests wurtzite structure with lattice constant 5.3876 A and average particle size of 4 nm which is confirmed by TEM micrographs. The bandgap of the synthesized ZnS nanoparticles are found to decrease with increase of PVA concentration. The Raman spectra of ZnS nanoparticles are also reported.

Nanoprobe Diffusion in Poly(Vinyl-alcohol) Gels and Solutions: Effects of pH and Dehydration

ABSTRACTWe report fluorescence correlation spectroscopy (FCS) measurements of the translational diffusion of two fluorescent nanoprobes, rhodamine (R6G) and carboxytetramethylrhodamine (TAMRA), embedded in poly(vinyl alcohol) (PVA) solutions and gels. The diffusion coefficient was measured as a function of the PVA concentration and pH. Furthermore, we designed and built an optical chamber to determine the diffusion coefficient of the nanoprobes within the PVA solutions and gels subjected to controlled dehydration. We find that 1) lowering pH causes an apparent slowing down of the diffusion of the nanoprobes, 2) increase of PVA concentration and crosslink density also induce slowing down of both nanoprobes, and 3) dehydration induces systematic decrease of the diffusion of TAMRA in both solutions and gels. Taken together, these results demonstrate that transient physical interactions between the nanoprobes and the PVA linear polymers have a significant effect upon nanoprobe diffusion.

Solvent-mediated amorphous-to-crystalline transformation of nitrendipine in amorphous particle suspensions containing polymers

The amorphous-to-crystalline transformation of nitrendipine was investigated using Raman spectroscopy and X-ray powder diffraction (XRPD). The nucleation and growth rate of crystalline nitrendipine in a medium containing poly (vinyl alcohol) (PVA) and polyethylene glycol (PEG 200) were quantitatively determined using image analysis based on polarized light microscopy. The findings from the image analysis revealed that the transformation process occurred through the dissolution of amorphous drug precipitate followed by the nucleation and growth of the crystalline phase with the amorphous precipitate acting as a reservoir for maintaining the supersaturation. The rates of nucleation and crystal growth of nitrendipine decreased with an increase in PEG 200 concentration in organic phase from 0% to 75% (v/v). Increasing the PVA concentration in water phase from 0.1% to 1.0% (w/w) also decreased the rates of nucleation and crystal growth, however, an increase in PVA concentration from 1.0% to 2.0% (w/w) did not result in a further decrease in the rates of nucleation and crystal growth. An increase in drug concentrations in the organic phase from 10mg/ml to 30mg/ml led to faster nucleation rates. However, a further increase in drug concentration to 100mg/ml decelerated the growth of nitrendipine crystals. Combining image analysis of polarized light micrographs together with Raman spectroscopy and XRPD provided an in-depth insight into solid state transformations in amorphous nitrendipine suspensions.

Organic Conductor Films: Fabrication and Characterization

Polypyrrole-poly(vinyl alcohol) (PPy-PVA) conducting polymer composite films were prepared on Indium Tin Oxide (ITO) glass electrode from an aqueous solution containing pyrrole monomer, p-toluenesulfonate electrolyte and poly(vinyl alcohol) insulating polymer by electrochemical method. The prepared composite films were characterized by conductivity and electromagnetic interference (EMI) shielding measurements, dynamic mechanical analysis (DMA) and optical microscopy. The conductivity data of PPy-PVA shows that with the increase in PVA concentration in aqueous pyrrole solution used to prepare the films, the conductivity of the prepared PPy-PVA composite films increased upto a certain level and later it showed a decreasing trend with further increase in PVA concentration used to prepare the composite films. The dynamic mechanical analysis (DMA) shows the evidence of the enhanced mechanical properties of PPy-PVA composite film over PPy film. The optical micrographs show the changes of morphology of the prepared composite films with the PVA concentration. The results of electromagnetic interference (EMI) shielding effectiveness measured in the microwave range of 8-12 GHz show that a shielding effectiveness of 45.67 dB was exhibited by PPy-PVA composite films.

Characterization of Genipin Crosslinked Hydrogels Composed of Chitosan and Partially Hydrolyzed Poly(vinyl alcohol)

AbstractChitosan and 80 % hydrolyzed poly(vinyl alcohol) (PVA) were used to prepare semi-interpenetrating networks of varying ratios of the constituents. The hydrogels were crosslinked using genipin, a naturally occurring nontoxic crosslinking agent. The swelling behavior of these hydrogels was studied in deionized water at 25, 35 and 45 °C and in media of different pH at 25 °C. The swelling behavior of the gels was found to be dependent on temperature, pH of the medium and the amount of PVA present in the gel. States of water in the hydrogels swollen at 25 °C and pH 7 were determined using Differential Scanning Calorimetry (DSC). The amount of freezing water in the swollen hydrogels increased whereas the amount of nonfreezing bound water decreased with the increase in PVA concentration in the gels. The gelation behaviour of the pregel solutions were also studied.

Chitosan-poly (vinyl alcohol)/poly (acrylonitrile) (CS–PVA/PAN) composite pervaporation membranes for the separation of ethanol–water solutions

Pervaporation (PV) membranes made of a chitosan (CS) homogeneous membrane, poly (vinyl alcohol)-poly (acrylonitrile) (PVA–PAN) and chitosan-poly (vinyl alcohol)/poly (acrylonitrile) (CS–PVA/PAN) composite membranes for the separation of ethanol–water solutions were manufactured. The swelling behaviors of CS homogeneous membranes and CS–PVA/PAN composite membranes were measured. Effects of membrane thickness, CS–PVA concentrations in the coating solution, PVA concentrations in the CS–PVA blend polymer, ethanol concentrations in the feed solutions and feed solution temperatures on pervaporation performance for the ethanol–water mixtures are discussed. The experimental results showed that the separation factor (α) of CS–PVA/PAN composite membranes increased with an increase of PVA concentration in the CS–PVA blend polymer from 0 to 40 wt%. With an increase in the membrane thickness from 12 to 18 μm, the separation factor (α) of the CS–PVA/PAN composite membrane increased while permeation flux ( J) decreased. With an increase of ethanol–water solution temperature, the separation factor (α) of CS membranes decreased and the permeation flux ( J) of CS membrane increased while for the PVA–PAN and CS–PVA/PAN composite membranes they increased. The apparent activation energy (Δ Ea) of water for CS membranes was 34.3–59.5KJ/mol and less than that of ethanol with 39.4–71.4 KJ/mol. The apparent activation energy (Δ Ea) of water for both PVA–PAN and CS–PVA/PAN membranes was twice as high as that of ethanol. The Δ Ea of water and ethanol for PVA/PAN and CS–PVA/PAN membranes was 13.6–61.6 KJ/mol, 3.3–15.1 KJ/mol, 41.0–60.6 KJ/mol, and 20.9–31.3 KJ/mol, respectively.

Molecular Origins of Wettability of Hydrophobic Poly(vinylidene fluoride) Microporous Membranes on Poly(vinyl alcohol) Adsorption: Surface and Interface Analysis by XPS

Irreversible adsorption of poly(vinyl alcohol) (PVA) on hydrophobic, porous poly(vinylidene fluoride) (PVDF) membranes was carried out using aqueous PVA solution. Water permeation was observed in PVDF microporous membranes after PVA adsorption, and maximum permeability was obtained after treatment with 4% PVA solution. Water permeability increased linearly with increasing PVA concentration up to 4%, and then a marginal decrease with a further increase in PVA concentration occurred. PVA adsorbed PVDF membranes were subjected to intense physicochemical analysis, especially with XPS. XPS results display the presence of an interface between PVA and PVDF, and the binding energy (BE) of the interface is low for the PVDF membranes treated with 4% PVA. Carbon from CF2-groups and F 1s core level clearly showed a decrease in its content on the surface after PVA adsorption and showed a minimum fluorine content at 4% PVA. F 1s BE shifts by 0.5 eV upon PVA adsorption and is independent of PVA concentration. EDAX analysis indicates that the bulk oxygen content remains within 4.5 +/- 0.6% and is independent of the PVA concentration. Nonetheless, a large amount of surface atom percentage of oxygen (20 +/- 4%) from O 1s core level shows an increase in PVA content on the surface of PVDF, and it is restricted mostly to the surface. The 4% PVA treated PVDF membrane clearly shows a broadening of O 1s core level to lower BE and indicates the interaction between PVDF and PVA which is significantly different compared to any other compositions. A new valence band feature at low BE, which is nonexistent on PVDF, develops after PVA adsorption. This indicates that the shift in the nature of the highest occupied molecular orbital (HOMO) derived mostly from oxygen; simultaneously, a suppression in the PVDF derived band indicates the change in nature of the PVA adsorbed surfaces from hydrophobic to hydrophilic. The above observations also suggest an irreversible electronic interaction between PVA and PVDF, possibly through charge transfer.

Stabilization of Individual Tubular J-Aggregates by Poly(vinyl alcohol)

The changes in the optical properties and morphology of J-aggregates formed by the 3,3‘-bis(3-carboxypropyl)-5,5‘,6,6‘-tetrachloro-1,1‘-dioctylbenzimidacarbocyanine dye (C8O3) in aqueous solution that are induced by the addition of poly(vinyl alcohol) (PVA) were investigated by optical spectroscopy and cryo-transmission electron microscopy (cryo-TEM). Upon increase of PVA concentration, aggregates evolve that show a similar tubular morphology as those in pure aqueous solution but with new spectroscopic features. The absorption spectrum of the modified J-aggregates differs from that of the unmodified aggregates by a shift of one of the four transitions that constitute the excitonic spectrum. Additionally, fluorescence emission is observed not only from the exciton band with lowest energy but also from a second band at higher energy. Measurements of the linear dichroism (LD) on oriented samples reveal that three of the transitions are polarized parallel to the long axis of the aggregates, while the fourth transition is polarized perpendicular. Cryo-TEM revealed a majority of individual tubular strands for PVA-containing solutions, which is different compared to pure C8O3 solutions showing bundles of tubular strands. The individual strands are assumed to be PVA-coated tubular aggregates being stabilized against bundling by repulsive forces induced by the adsorbed polymer chains. The spectroscopic changes are ascribed to slight rearrangements in the molecular packing of dye molecules upon binding of PVA to the aggregates.

Air compartment multiple-unit system for prolonged gastric residence. Part I. Formulation study

A pre-formulation study was directed to optimize the in vitro floating ability of an air compartment multiple-unit system. Each unit was formed by a coated bead composed of a calcium alginate core separated by an air compartment from a calcium alginate or calcium alginate/polyvinylalcohol (PVA) membrane. The floating ability depended on the presence of the air compartment and on membrane porosity. The porous structure generated by the leaching of PVA, employed as a water-soluble additive in the coating composition, increased the membrane permeability preventing air compartment shrinkage. In this way, units were produced which were able to float immediately upon contact with artificial gastric juice and for a long period of time. The floating ability increased with the increase in PVA concentration and molecular weight and it was found to be excellent when using PVA 100 000 at a concentration of at least 5%.