Molecular Weight Of PVA Research Articles

Effect of Degree of Saponification and Molecular Weights of PVA on Properties of Low Density Foam-formed Sheets

Effect of Degree of Saponification and Molecular Weights of PVA on Properties of Low Density Foam-formed Sheets

DEVELOPMENT AND OPTIMIZATION OF INDOMETHACIN NANOSUSPENSIONS USING DESIGN OF EXPERIMENT APPROACHES

ABSTRACT
 Objective: In this study, it was aimed to prepare nanosuspensions that contains Indomethacin which is a BCS class II drug. To assess the cumulative impact of the chosen variables on the nanosuspension properties, a 34 factorial design was applied and particle size and distributions were examined.
 Material and Method: In the study, the solvent/antisolvent method was used in the preparation of the suspensions. 34 factorial design. Design-Expert software was used for evaluation of the prepared formulations in order to obtain the best formulation. PVA ratio, PVA molecular weight, solvent/antisolvent ratio, and ethanol/PEG ratio were used as independent design parameters, and their effects on particle size and distribution were examined.
 Result and Discussion: Nanosuspensions were successfully prepared by the solvent/antisolvent method. Particle size and polydispersity index of the nanosuspensions were found to be affected by both molecular weight and percentage of PVA in the anti-solvent phase (p ˂ 0.05). 0.2% PVA; molecular weight of 31 000 for PVA and the solvent-antisolvent ratio as 3:50 were found to be the optimal parameters for the nanosuspension formulations. The particle size and polydispersity of optimum formulation was found 301.5 ± 31.1 nm and 0.159 ± 0.035, respectively.
 
 Keywords: Factorial design, indomethacin, nanosuspension, solvent/antisolvent method

Biomimetic ice recrystallization inhibition-active poly(vinyl alcohol) enhances the freeze-thaw resistance of cement paste

This work presents experimental evidence that specific molecular weights of poly(vinyl alcohol) (PVA), a molecule that displays biomimetic ice recrystallization inhibition (IRI) behavior, are required to impart freeze-thaw resistance to portland cement paste when PVA is added as a water-solubilized admixture. Three molecular weights of PVA were first tested for IRI activity. IRI-active PVA-modified cement pastes were then prepared and tested for freeze-thaw resistance. X-ray micro-computed tomography was employed to investigate internal damage and to characterize the air void system. Differential scanning calorimetry was used to quantify and compare the amount of ice that formed in the hardened pastes. Mercury intrusion porosimetry was used to characterize the pore-size distributions of cement pastes. Results substantiate that PVA with a molecular weights >31,000 g/mol can impart freeze-thaw resistance to cement paste and that the freeze-thaw enhancement is not due to improved hydrophobicity or an adequately entrained air void system. PVA additions did lead to reductions in porosity. However, the reductions were insufficient to fully explain why lower quantities of ice formed during freezing, indicating that IRI-active biomimetic polymers, like PVA, can enhance the freeze-thaw resistance of cement paste due, in part, to their interaction with ice.

New Cryogels Based on Poly(vinyl alcohol) and a Copolymacrolactone System: I-Synthesis and Characterization.

Physical cryogels were obtained using the successive freeze–thaw technique of poly(vinyl alcohol) (PVA)/poly(ethylene brassylate-co-squaric acid) (PEBSA) solutions. The cryogel systems were prepared by using two different molecular weights of PVA and PEBSA with three different ratios between the ethylene brassylate (EB) and squaric acid (SA) comonomers. The presence of interactions, the thermal properties and the morphology were investigated using Fourier Transform Infrared Spectroscopy (FT-IR), thermogravimetry (TGA and DTG) and scanning electron microscopy (SEM), respectively. The influence of the composition on the degree of swelling in a physiological environment was demonstrated. The study highlighted improvements in terms of new network flexibility due to the intermolecular chains interactions brought by the introduction of PEBSA in the cryogel structure. We also concluded that the presence of PEBSA in the PVA/PEBSA cryogel network improved the loading capacity of the new system with specific hydrophobic agents, for example essential oils, which (due to their antimicrobial character) can lead to the use of new systems obtained for various applications.

Effect of Vinyl Acetate Ethylene Emulsion Formulation and Poly (vinyl alcohol) Molecular Weight on the Quality of Inkjet Paper

The study aim was to evaluate the effect of mixing of a water-soluble polymer, poly (vinyl alcohol) (PVA), and an emulsion binder, vinyl acetate ethylene (VAE), on the properties of the coating color and to identify the factors affecting the design of the coating color formulation for inkjet paper. The test compositions of the coating color used PVA and VAE emulsion binders of different molecular weights, and the properties of the prepared coating color and coated paper were analyzed. As the mixing ratio of the VAE emulsion to PVA increased, the viscosity of the coating solution decreased, but when the mixing ratio was constant, the coating color using low-molecular weight PVA had low viscosity. As the VAE emulsion mixing ratio and PVA molecular weight increased, the contact angle of the coated papers increased, but the ink density of the coated paper decreased.

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops.

Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w/v. The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.

Characterization of Acoustic, Cavitation, and Thermal Properties of Poly(vinyl alcohol) Hydrogels for Use as Therapeutic Ultrasound Tissue Mimics.

The thermal and mechanical effects induced in tissue by ultrasound can be exploited for therapeutic applications. Tissue-mimicking materials (TMMs), reflecting different soft tissue properties, are required for experimental evaluation of therapeutic potential. In the study described here, poly(vinyl alcohol) (PVA) hydrogels were characterized. Hydrogels prepared using different concentrations (5%-20% w/w) and molecular weights of PVA ± cellulose scatterers (2.5%-10% w/w) were characterized acoustically (sound speed, attenuation) as a function of temperature (25°C-45°C), thermally (thermal conductivity, specific heat capacity) and in terms of their cavitation thresholds. Results were compared with measurements in fresh sheep tissue (kidney, liver, spleen). Sound speed depended most strongly on PVA concentration, and attenuation, on cellulose content. For the range of formulations investigated, the PVA gel acoustic properties (sound speed: 1532 ± 17 to 1590 ± 9 m/s, attenuation coefficient: 0.08 ± 0.01 to 0.37 ± 0.02 dB/cm) fell within those measured in fresh tissue. Cavitation thresholds for 10% PVA hydrogels (50% occurrence: 4.1-5.4 MPa, 75% occurrence: 5.4-8.2 MPa) decreased with increasing cellulose content. In summary, PVA cellulose composite hydrogels may be suitable mimics of acoustic, cavitation and thermal properties of soft tissue for a number of therapeutic ultrasound applications.

Propolis Integration Methods into Solutions for Highly Loaded Propolis Fibers by Needleless Electrospinning.

A load-bearing matrix filled with biologically active compounds is an efficient method for transporting them to the target location. Bee-made propolis has long been known as a natural product with antibacterial and antiviral, anti-inflammatory, antifungal properties, and anti-oxidative activity. The aim of the research is to obtain stable propolis/PVA solutions and produce fibers by electrospinning. To increase propolis content in fibers as much as possible, various types of propolis extracts were used. As a result of the research, micro- and nano-fiber webs were obtained, the possible use of which have biomedical and bioprotective applications. All used materials are edible and safe for humans, and fiber webs were prepared without using any toxic agent. This strategy overcomes propolis processing problems due to limitations to its solubility. The integration of different combinations of extracts allows more than 73 wt% of propolis to be incorporated into the fibers. The spinning solution preparation method was adapted to each type of propolis, and by combining the methods, solutions with different propolis extracts were obtained. Firstly, the total content of flavonoids in the propolis extracts was determined for the assessment and prediction of bioactivity. The properties of the extracts relevant for the preparation of electrospinning solutions were also evaluated. Secondly, the most appropriate choice of PVA molecular weight was made in order not to subject the propolis to too high temperatures (to save resources and not reduce the bioactivity of propolis) during the solution preparation process and to obtain fibers with the smallest possible diameter (for larger surface-to-volume ratios of nanofibers and high porosity). Third, electrospinning solutions were evaluated (viscosity, pH, conductivity and density, shelf life) before and after the addition of propolis to predict the maximum propolis content in the fibers and spinning stability. Each solution combination was spun using a cylindrical type electrode (suitable for industrial production) and tested for a stable electrospinning process. Using adapted solution-mixing sequences, all the obtained solutions were spun stably, and homogeneous fibers were obtained without major defects.

The dynamic viscoelastic characterisation and magnetic resonance imaging of poly(vinyl alcohol) cryogel: Identifying new attributes and opportunities

Poly(vinyl alcohol) (PVA) cryogel is a biocompatible, synthetic hydrogel, compatible with magnetic resonance (MR) imaging. It is widely used as a biomaterial in tissue scaffolds and mimics to test various diagnostic techniques. The aim of this study is to characterise the effect of varying PVA concentration, molecular weight (MW) and manufacturing protocol on the viscoelastic mechanical properties and MR T2 relaxation time. Further to this MR imaging (MRI) was investigated as a method to quantify material homogeneity. Cylindrical samples of PVA, of varying MW, concentration and number of freeze thaw cycles (FTCs), were manufactured. Dynamic mechanical analysis was performed to evaluate the storage and loss moduli between frequencies of 0.5 and 10 Hz. MR T2 relaxation maps were imaged using a 7 T MRI instrument. Storage and loss moduli were shown to increase with MW, concentration, or the number of FTCs; with storage modulus ranging from 55 kPa to 912 kPa and loss modulus ranging from 6 kPa to 103 kPa. MR T2 relaxation time was shown to increase linearly with PVA concentration. The qualitative and quantitative heterogeneity of the PVA sample were identified through MR T2 relaxation time maps. Excitingly, PVA demonstrated a composition-dependent casual correlation between the viscoelastic mechanical properties and MR T2 relaxation time. In conclusion, this research thoroughly characterised the viscoelastic mechanical properties of PVA to support its extensive use as a biomaterial, and demonstrated the use of MRI to non-invasively identify sample heterogeneity and to predict the composition-dependent viscoelastic properties of PVA.

Synthesis of a PVA drug delivery system for controlled release of a Tramadol\u2013Dexketoprofen combination

The local administration of analgesic combinations by means of degradable polymeric drug delivery systems is an alternative for the management of postoperative pain. We formulated a Tramadol–Dexketoprofen combination (TDC) loaded in poly(vinyl alcohol) (PVA) film. Films were prepared by the solvent casting method using three different molecular weights of PVA and crosslinking those films with citric acid, with the objective of controlling the drug release rate, which was evaluated by UV–vis spectrometry. Non-crosslinked PVA films were also evaluated in the experiments. Differential scanning calorimetry (DSC) analysis of samples corroborated the crosslinking of PVA by the citric acid. Blank and loaded PVA films were tested in vitro for its impact on blood coagulation prothrombin time (PT) and partial thromboplastin time (PTT). The swelling capacity was also evaluated. Crosslinked PVA films of higher-molecular weight showed a prolonged release rate compared with that of the lower-molecular-weight films tested. Non-crosslinked PVA films released 11–14% of TDC. Crosslinked PVA films released 80% of the TDC loaded (p < 0.05). This suggests that crosslinking films can modify the drug release rate. The blank and loaded PVA films induced PT and PTT in the normal range. The results showed that the polymeric films evaluated here have the appropriate properties to allow films to be placed directly on surgical wounds and have the capacity for controlled drug release to promote local analgesia for the control of postoperative pain.

Influence of molecular weight of polymer dielectric on the photo-response of solution-processed OFETs

The crucial role of molecular weight of the polymer dielectric in regulating the electrical performance and photo-response of TIPS-pentacene OFETs has been explored using poly(vinyl alcohol) (PVA) as the polymer dielectric layer. With increasing molecular weight of PVA, a degradation in the electrical and photo-response was observed. Atomic-force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR) and X-ray Diffraction (XRD) studies revealed that with increase in PVA molecular weight, polarizability of PVA dielectric layer and thus strength of the OFET channel reduced due to decreased hydroxyl group concentration oriented perpendicular to the PVA-semiconductor interface. Further, due to rising surface roughness of underlying PVA film with its molecular weight, macroscopic irregularities and therefore trap density in the active layer grown over it also increases. Therefore, both of these molecular weight dependent factors influence overall device performance and photo-response of OFETs in a critical way.

Performance-tuning of PVA-based gel electrolytes by acid/PVA ratio and PVA molecular weight

The significant breakthroughs of flexible gel electrolytes have attracted extensive attention in modern wearable electronic gadgets. The lack of all-around high-performing gels limits the advantages of such devices for practical applications. To this end, developing a multi-functional gel architecture with superior ionic conductivity while enjoying good mechanical flexibility is a bottleneck to overcome. Herein, an architecturally engineered gel, based on PVA and H3PO4 with different molecular weights of PVA for various PVA/H3PO4 ratios, was developed. The results show the dependence of ionic conductivity on molecular weight and also charge carrier concentration. Consequently, fine-tuning of PVA-based gels through a simple yet systematic and well-regulated strategy to achieve highly ion-conducting gels, with the highest ionic conductivity of 14.75 ± 1.39 mS cm-1 have been made to fulfill the requirement of flexible devices. More importantly, gel electrolytes possess good mechanical robustness while exhibiting high-elasticity (%766.66 ± 59.73), making it an appropriate candidate for flexible devices.

Lotus-Root-Like Microchanneled Collagen Scaffold.

In the human body, there are numerous microtubular tissue structures, such as muscles, vessels, nerves, and tendons. Tissue engineering scaffolds have been regarded as a high-potential candidate for providing such aligned instructive niches to facilitate cell-recruitment and differentiation, and eventually, successful tissue regeneration. Moreover, scaffolds derived from the extracellular matrix (ECM) can provide excellent biocompatibility. However, the fabrication of such microtubular hierarchical scaffolds using ECM has proven to be difficult, and thus, innovative fabrication approaches are required. Herein, we have developed a biofabrication system involving a sequential removal of supporting materials (polycaprolactone (PCL) and poly(vinyl alcohol) (PVA)) to fabricate a uniaxially aligned microtubular collagen scaffold, a lotus-like structure. To generate the unique morphological structures of the scaffold, we manipulated various material-related and processing factors, such as the molecular weight of PVA and the weight fraction of collagen coating. Physical and biological activities of the aligned hierarchical microtubular collagen scaffolds were compared with those of the controls (conventional collagen struts and microtubular collagen scaffolds void of a uniaxial topographical cue). In conclusion, the instructive niche on the aligned hierarchical microtubular collagen structure induced high degrees of myoblast alignment and efficient myogenic differentiation.

Electrospinning Fabrication of Poly(vinyl alcohol)/Coptis chinensis Extract Nanofibers for Antimicrobial Exploits.

Coptis chinensis (CC) is used in conventional Chinese medicine. The main active components of CC are isoquinoline alkaloids, including berberine, coptisine, palmatine, and magnoflorine; all these are known to have several pharmacological properties. Poly(vinyl alcohol) (PVA) is a well-known synthetic biocompatible polymer suitable for a range of pharmaceutical uses; it can be used as a matrix for the incorporation of functional materials and has a wide range of applications in the cosmetics, food, pharmaceutical, and packaging industries. In this study, PVA-based electrospun nanofibers containing CC extract were successfully fabricated. Furthermore, the effects of different CC extract contents on the morphologies, and antimicrobial and antifungal properties of PVA/CC extract nanofibers were investigated. Morphological changes were observed using different molecular weights of PVA. For characterization, field-emission scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared analysis were performed. The effectiveness of these nanofibers has been demonstrated by evaluating the thermal stability against Staphylococcus aureus, antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis, and the antifungal activity against the fungi Aureobasidium pullulans and Penicillium pinophilum. The PVA/CC extract nanofibers were found to have excellent antibacterial and antifungal activity and thermal stability; hence, their use in medicinal sectors is highly recommended.

PVA/Dextran hydrogel patches as delivery system of antioxidant astaxanthin: a cardiovascular approach

After myocardial infarction, the heart’s mechanical properties and its intrinsic capability to recover are compromised. To improve this recovery, several groups have developed cardiac patches based on different biomaterials strategies. Here, we developed polyvinylalcohol/dextran (PVA/Dex) elastic hydrogel patches, obtained through the freeze thawing (FT) process, with the aim to deliver locally a potent natural antioxidant molecule, astaxanthin, and to assist the heart’s response against the generated myofibril stress. Extensive rheological and dynamo-mechanical characterization of the effect of the PVA molecular weight, number of freeze-thawing cycles and Dex addition on the mechanical properties of the resulting hydrogels, were carried out. Hydrogel systems based on PVA 145 kDa and PVA 47 kDa blended with Dex 40 kDa, were chosen as the most promising candidates for this application. In order to improve astaxanthin solubility, an inclusion system using hydroxypropyl-β-cyclodextrin was prepared. This system was posteriorly loaded within the PVA/Dex hydrogels. PVA145/Dex 1FT and PVA47/Dex 3FT showed the best rheological and mechanical properties when compared to the other studied systems; environmental scanning electron microscope and confocal imaging evidenced a porous structure of the hydrogels allowing astaxanthin release. In vitro cellular behavior was analyzed after 24 h of contact with astaxanthin-loaded hydrogels. In vivo subcutaneous biocompatibility was performed in rats using PVA145/Dex 1FT, as the best compromise between mechanical support and astaxanthin delivery. Finally, ex vivo and in vivo experiments showed good mechanical and compatibility properties of this hydrogel. The obtained results showed that the studied materials have a potential to be used as myocardial patches to assist infarcted heart mechanical function and to reduce oxidative stress by the in situ release of astaxanthin.

Synthesis of poly(vinyl alcohol‐graft‐hyperbranched glycerol)

ABSTRACTWe report the first example of grafting hyperbranched polyglycerol onto poly(vinyl alcohol) via ring‐opening polymerisation of glycidol to prepare poly(vinyl alcohol‐graft‐hyperbranched glycerol) (P[(VA)‐g‐(hPG)]). The effects of catalyst, molecular weight of PVA, reaction temperature, water content, moles of reagent, and addition time of reagent were also investigated. P[(VA)‐g‐(hPG)] with various mole fractions of hPG were prepared and the degrees of substitution and branching were determined. P[(VA)‐g‐(hPG)] displayed decreased degree of crystallinity and also increased solubility in water, compared to PVA. P[(VA)‐g‐(hPG)] is shown to be a superior hair styling polymer with a curl retention value of 85% after 4 h. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3041–3047

Screening and characterisation of a poly(vinyl alcohol)-degrading mixed microbial culture

A mixed microbial culture, which can degrade poly(vinyl alcohol) (PVA), was screened from the activated sludge of a textile factory. This mixed culture was found to consist of many bacterial strains, including representatives of Pseudomonas, Sphingopyxis, Castellaniella, Stenotrophomonas, Ochrobactrum and Shinella. The relative abundance of strains in the mixed culture during the incubation period was determined through the Illumina Miseq Platform. The biodegradation of PVA by this mixed culture in liquid medium was determined using several methods, including UV and gel-permeation chromatography (GPC). When the mixed culture was incubated in PVA1799-containing mineral medium for 4.5 days, the concentration of PVA decreased by 91% and the mean weight-average molecular weight of PVA decreased by 68%. The PVA-degrading enzymes produced by the mixed culture appear to be membrane or intracellular enzyme. The optimum pH and temperature for PVA-degrading enzyme activity were investigated by single-factor tests and were discovered to be pH 7.0 and 40°C, respectively. The crude enzymes extracted from the mixed culture could partly degrade PVA1799 nanofibre scaffolds.

Separation performance of poly(vinyl alcohol) based nanofiltration membranes crosslinked by malic acid for salt solutions

In this study, poly(vinyl alcohol) (PVA) based nanofiltration (NF) membranes were prepared by coating a thin PVA film on polysulfone ultrafiltration support substrates. The PVA film was cross-linked using malic acid in the presence of HCl as a catalyst. The impacts of crosslinker content and PVA molecular weight on physicochemical properties and separation performance of the prepared membranes were investigated. The obtained membranes were characterized using FTIR spectra, swelling degree, and sessile drop contact angles, respectively. Then, the separation performance of the NF membrane was systematically evaluated for pure water; magnesium sulfate (MgSO4) as well as sodium chloride (NaCl) solutions using a custom fabricated 4-cell crossflow desalination system. On increasing the malic acid content, the extent of crosslinking degree increased and disrupted the crystallinity of the PVA film. The salt rejection of the prepared membranes was found to increase and then decrease through the maximum point of malic acid content for 20 wt%, while the water permeability showed the opposite trend. Moreover, the results revealed that the prepared membrane with higher molecular weight exhibited lower water permeability but better salt rejection.

Effect of molecular weight of PEG or PVA as reducing-stabilizing agent in the green synthesis of silver-nanoparticles

Silver nanoparticles (Ag-NPs) have been prepared by a green chemistry method using PEG or PVA, as reducing-stabilizing agent, and characterized using UV–vis, SEM-EDS, AFM and TEM. A comparative study was done to determine the PEG or PVA molecular weight (Mw) effect, on shape, size and dispersity of Ag-NPs. Lower Mw of PEG or PVA results in small Ag-NPs. The synthesized Ag-NPs were spherical with an average size of 2–30nm (PEG measured by TEM), and 2.5–45nm (PVA measured by TEM). Furthermore, photocatalytic degradation of Putnam sky-blue 39 was measured spectrophotometrically using Ag-NPs under sun light illumination, with 97% efficiency.

Microparticles produced by the hydrogel template method for sustained drug delivery

Polymeric microparticles have been used widely for sustained drug delivery. Current methods of microparticle production can be improved by making homogeneous particles in size and shape, increasing the drug loading, and controlling the initial burst release. In the current study, the hydrogel template method was used to produce homogeneous poly(lactide-co-glycolide) (PLGA) microparticles and to examine formulation and process-related parameters. Poly(vinyl alcohol) (PVA) was used to make hydrogel templates. The parameters examined include PVA molecular weight, type of PLGA (as characterized by lactide content, inherent viscosity), polymer concentration, drug concentration and composition of solvent system. Three model compounds studied were risperidone, methylprednisolone acetate and paclitaxel. The ability of the hydrogel template method to produce microparticles with good conformity to template was dependent on molecular weight of PVA and viscosity of the PLGA solution. Drug loading and encapsulation efficiency were found to be influenced by PLGA lactide content, polymer concentration and composition of the solvent system. The drug loading and encapsulation efficiency were 28.7% and 82% for risperidone, 31.5% and 90% for methylprednisolone acetate, and 32.2% and 92% for paclitaxel, respectively. For all three drugs, release was sustained for weeks, and the in vitro release profile of risperidone was comparable to that of microparticles prepared using the conventional emulsion method. The hydrogel template method provides a new approach of manipulating microparticles.