Sharif Digital Repository

In this study, physically cross-linked hydrogels were developed by freezing-thawing method while different concentrations of honey were included into the hydrogels for accelerated wound healing. The hydrogel was composed of chitosan, polyvinyl alcohol (PVA), and gelatin with the ratio of 2:1:1 (v/v), respectively. Further, the effect of honey concentrations on antibacterial properties, and cell behavior was investigated. In vivo studies, including wound healing mechanism using rat model and histological analysis of section tissue samples were performed. The results illustrated that the incorporation of honey in hydrogels increased the ultimate strain of hydrogels approximately two times,... 

The influence of particle size and surface modification on sonocatalytic activity of TiO2 nanoparticles was investigated by measuring the degradation efficiency of methyl orange (MO) as a model pollutant. Crystalline TiO2 nanoparticles with different particles and aggregate size were prepared through solution-phase method with varying synthesis temperatures. Coating with polyvinyl alcohol was performed to enhance colloidal stability of the particles over a wide range of pH values (1.5–7.5). Characterization was carried out using X-ray diffraction, high-resolution transmission electron microscopy, dynamic light scattering, and Fourier-transformed infrared techniques. It was found that... 

Poly(vinyl alcohol)/graphene oxide mixed matrix membranes have been prepared and applied for the pervaporation of isooctane (aliphatic) and toluene (aromatic) mixtures. Characteristics of the membranes such as crystallinity, morphology, and swelling have been investigated, and the results have been used to describe pervaporation performance. Experimental tests evidenced that incorporation of low content of graphene oxide nanoplates (0.5 wt%) in poly(vinyl alcohol) increases affinity of the membrane to aromatics by S and π bonds and selectivity increase to about four times. Moreover, interaction of graphene oxide with toluene results in increasing of swelling and decreasing of permeation... 

Although Multi-Walled Carbon NanoTubes (MWCNTs) are found to influence the rheological behavior of drilling fluids, there are yet some controversies regarding their performance towards reducing formation damage induced by the invasion of water-based drilling fluids (WBFs). To address this important question, we synthesized novel nanocomposite materials via modifying the MWCNT via varying the proportion of carboxylated MWCNTs to PolyVinyl Alcohol (PVA). These nanocomposites were then used to make nano-based drilling-fluids (NDFs). The performance of the NDFs was evaluated by a set of rheological behavior tests, filtration experiments, and core-scale mud flow tests. To distinguish between the... 

Due to the hopeful potential of nanoparticles in medicine, they have attracted much attention for various applications such as targeted drug/gene delivery, separation or imaging. Interaction of NPs with the biological environment can lead to a wide range of cellular responses. In order to have safe NPs for biomedical applications, the current biocompatibility researches are particularly focused on the severe toxic mechanisms which cause cells death. These mechanisms are apoptosis, autophagy and necrosis, which can also be intricately linked with the cell-life cycle, as there are various check-points and controls in a cell's life cycle to ensure appropriate division processes. Mechanisms by... 

Removal of aromatic compounds from fuel is an essential requirement in new environmental policies. In the present study, poly(vinyl alcohol)/graphene oxide (GO) mixed matrix membranes were prepared and applied to the separation of toluene from iso-octane by pervaporation, considering the similarity and interaction between graphene and aromatics. The effects of crosslinking and GO content on separation efficiency have been investigated in detail. Owing to the high affinity of GO with toluene through s and π bonds, the selectivity of the membranes was increased by incorporating a low amount of GO. The results also indicated that noncrosslinked membranes have higher selectivity and permeation... 

In this study, the properties of poly (vinyl alcohol)(PVA) films incorporated with Zataria multiflora essential oil (ZMO) as a potential antioxidant/antibacterial material was investigated. PVA films were prepared from PVA solutions (2% w/v) containing different concentrations of ZMO. Water solubility, moisture absorption, water swelling, and water vapor permeability for pure PVA films were 57 ± 1.1, 99 ± 3.2%, 337 ± 8%, and 0.453 ± 0.015 g mm/m2 h, respectively. Incorporation of ZMO into PVA films caused a significant decrease in water swelling and moisture absorption and increase in solubility and water vapor permeability. Tensile strength, elastic modulus, and elongation at break for pure... 

Foams for biomedical applications were made from polyvinyl alcohol, polyvinyl alcohol / polyvinyl pyrrolidone blend and their nanocomposites with nanoclay by clean processes. Air was entrapped into the aqueous polymer solutions during vigorous mixing and then the solutions were freeze-dried. The foams structure was stabilized by crosslinking via gamma irradiation without using any harmful chemicals. The hydrophilic biocompatible foams possessed interconnected open cell structure with remarkable capacity to absorb and retain water. The foams in wet state were soft and flexible. Desirable pore structure and higher water absorption was obtained at a solution concentration of 5 wt% for both... 

The effect of graphene (G) and graphene oxide (GO), used as the nanofiller in polymer nanocomposites (NC), on the structural and dynamic properties of polymer chains, has been studied by means of molecular dynamics (MD) simulations. Two polymers, i.e., poly(propylene) and poly(vinyl alcohol), are employed as matrices to cover a wider range of polymer–filler interactions. The local structural properties, e.g., density profile, average Rg, and end-to-end distance as well as dynamic properties, e.g., estimated translational and orientational relaxation times, of polymer chains are studied. In addition, the interaction energies are estimated between polymers and nanofillers for different hybrid... 

Poly (vinyl alcohol) and nano-diamond, PVA/ND, hydrogels were prepared and assessed as prosthetic material suitable for replacement of the nucleus pulposus. The hydrogels were prepared by gamma irradiation at various doses (15 kGy, 25 kGy, 35 kGy, 45 kGy) and at various ND concentrations ranging from 0.25 wt.% to 3 wt.%. Extent of gelation, equilibrium water content, and viscoelastic properties of swelled hydrogels at definite water contents were measured and examined as a function of ND concentration as well as gamma dose. According to viscoelastic measurements, the strength of hydrogels increased considerably over that of pure PVA at a low concentration of ND. By increasing irradiation... 

Barrier properties of the biaxial oriented polypropylene (BOPP) films are the most important properties in food packaging industry. In this study different compatibilizers and materials were examined in order to find an appropriate blend composition to minimize the oxygen permeability of the films. It was observed that using organoclay and nanocomposits have positive effect on the oxygen permeability although the kind of compatibilizer is important. Through all evaluated materials the PVA (Poly(vinyl alcohol)) and MA (Maleic Anhydride) were the most successful selection for this goal. The BOPP film blended by PVA achieved the lowest oxygen transfer rate (300 cc 20 μm/m2 24 h atm) in compared... 

Poly (vinyl alcohol)/graphene oxide (PVA/GO) gamma irradiated nanocomposite films and hydrogels were prepared. In composite films, GO was initially irradiated by gamma ray in order to improve interactions between GO and PVA. The film containing 1 wt-% GO was very strong where tensile modulus and tensile yield strength were 45 and 115% higher than those of pure PVA. In the second set of experiments PVA/GO hydrogels were made by irradiating PVA/GO suspensions by gamma ray at various doses. It was an interesting finding that GO increased the gel portion of hydrogels through contribution of H-bonds between PVA and GO. The hydrogels prepared at 20 kGy had remarkable water swelling ratio that... 

In this paper, the flow behavior of Leonov-Like conformational rheological model, which has root in the generalized Poisson bracket formalism based on the conformation tensor, have been studied in the circular die flow. Prediction of the normal stress differences during the flow of these fluids lets us to follow and calculate relaxation dependent phenomena such as die swell. The model predictions have been compared for the four families of mobility expressions. The Study of the model prediction sensitivity to its mobility term shows that model predictions can cover a wide range of rheological behaviors generally observed for polymer melts and solutions in the circular die flow. Copyright ©... 

Nature-inspired coating with polydopamine (PDA) is a promising way to improve the performance of graphene oxide (GO) based nanocomposites due to its high ability to enhance interactions in matrix-disperse systems. Here, we examined the capability of two types of PDA to develop the reinforced polyvinyl alcohol (PVA)/GO hydrogels. In the first mode, dopamine hydrochloride was polymerized as nanoparticles and then incorporated into PVA solution with GO nanoplatelets (P-NG hydrogel). In the second mode, polydopamine was polymerized in the presence of GO nanoparticles to obtain PDA surface-modified GO and then PVA nanocomposite hydrogel (P-CG sample). Rheological and tensile findings revealed... 

In this study, polyvinyl alcohol hydrogel chains were crosslinked by polyurethane in order to synthesize a suitable substrate for cartilage lesions. The substrate was fully characterized, and in vitro and in vivo investigations were conducted based on a sheep model. In vitro tests were performed based on the chondrocyte cells with the Alcian Blue and safranin O staining in order to prove the presence of proteoglycan on the surface of the synthesized substrate, which has been secreted by cultures of chondrocytes. Furthermore, the expression of collagen type I, collagen type II, aggrecan, and Sox9 was presented in the chondrocyte cultures on the synthesized substrate through RT-PCR. In... 

Surface modified magnetic nanoparticles (M-NPs) were synthetized and stabilized in poly (vinylalcohol) solution. The solutions with various magnetic nanoparticles contents were gammairradiated and magnetic poly (vinyl-alcohol) (M-PVA) hydrogels were synthesized. The magnetic hydrogels and also the un-irradiated magnetic poly (vinyl alcohol) nanocomposite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FTIR) and mechanical measurement. The M-NPs were uniformly dispersed in the polymer matrix due to a strong interaction between the surface-modified M-NPs and polymer matrix.... 

Polyvinyl alcohol (PVA) thin films were reinforced by glutaraldehyde and multiwalled carbon nanotubes (MWCNTs) and then mechanical, water solubility, water swelling, water uptake, water vapor permeability, and antibacterial properties of the films were examined. Cross-linking by glutaraldehyde or incorporation of MWCNT caused a significant increase in tensile strength, decrease in elongation at break, and increase in Young's modulus of the PVA films, while MWCNTs were more effective rather than that of glutaraldehyde. Cross-linking by glutaraldehyde or incorporation of MWCNT caused a significant decrease in water solubility, water swelling and water uptake, with a similar manner.... 

Poly(vinyl alcohol)-polyethylene glycol, PVA-PEG, blended membrane were prepared using supercritical fluid assisted phase-inversion method, in which scCO2 was used as the anti-solvent. Poly(vinyl alcohol) was utilized as the main polymer, polyethylene glycol as the additive, and dimethyl sulfoxide (DMSO) as the solvent of these polymers. Taguchi method was used to investigate the effect of some operating parameters on the morphology of the membranes. The L16 orthogonal array was selected under the following conditions: pressure (100, 135, 165 and 200 bar), temperature (40, 45, 50 and 55°C) and PEG weight percent (0, 0.33, 0.66, and 1%). Total polymer concentration of solutions in all... 

Salep, known as a biodegradable polysaccharide, is hydrolyzed and used as both a reducing agent and stabilizer for graphene oxide (GO). The functionalized reduced graphene oxide (f-rGO) is homogenously dispersed in an aqueous solution of poly(vinyl alcohol) (PVA). PVA based hydrogel and film nanocomposites are prepared and proposed as new biomaterials for tissue engineering applications. The mechanical properties of the film nanocomposites are investigated with varying content of f-rGO, glycerol and citric acid as a reinforcing agent, a plasticizer agent and a cross linking agent respectively. For the first time, chemically cross linked PVA hydrogels are synthesized using... 

In this study, a fast and sensitive flow injection μ-solid phase extraction (FI-μ-SPE) technique based on an electrospun polyaniline (PANI) nanocomposite in conjunction with gas chromatography-mass spectrometry (GC-MS) was developed. The PANI-based nanocomposite was synthesized by electrospinning of a solution containing polyvinyl alcohol (PVA)/PANI. The majority of PVA template was subsequently removed from the whole PVA/PANI nanofibers blend by exposing the electrospun nanocomposite to hot water. The homogeneity, porosity and characterization of the electrospun nanofibers were investigated by the scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Due to...