Low Molecular Weight Poly Vinyl Research Articles

Universal 2D material film transfer using a novel low molecular weight polyvinyl acetate

Polyvinyl acetate (PVAc) is used as a rigid support layer during transfer process of large area chemical vapor deposition (CVD)-grown two-dimensional (2D) materials onto desirable target substrates without incorporating structural and chemical damages. The PVAc as a support layer provides key advantages suitable for transfer of high-quality large-area 2D materials, such as an excellent room-temperature solubility in chemical solvents (including acetone, methanol, and ethanol), a robust support, and low-cost. To demonstrate that our PVAc assisted transfer method exhibits a reliable performance, we measured 100 devices employing graphene transferred by each polymer medium. The PVAc assisted transfer technique enables graphene to achieve a high carrier mobility of up to ~ 10,000 cm2 V−1 s−1 at room temperature having smaller standard deviation compared to those of the graphene transferred via other transfer methods, indicating that the quality of the as-transferred 2D materials is not only mainly determined by the quality of the as-synthesized 2D materials, but also by defects incurred during the transfer process. Our novel transfer technique will enable application studies of 2D materials to large area electronic and optoelectronic devices.

Response surface methodology optimization of electrospinning process parameters to fabricate aligned polyvinyl butyral nanofibers for interlaminar toughening of phenolic-based composite laminates

In this study and for the first time, aligned nanofibers were produced from low molecular weight polyvinyl butyral. Using response surface methodology, the preparation condition of aligned nanofiber was optimized in terms of nanofiber diameter and its structural stability. Central composite design as a response surface methodology was employed and the effects of process variables and their influence on nanofiber diameter were investigated. Based on a statistical analysis, the use of a model, which was used to determine the nanofiber diameter, proved to be successful because of its low probability value (0.0073) and high correlation coefficient (0.9619). A high-speed cylinder collector was used to fabricate aligned polyvinyl butyral nanofibers. The optimum conditions of 17.5 kV voltage, 10 cm collector distance, 13% solution concentration, and 2100 r/min rotational speed were obtained from experiments. The least diameter of 158.6 nm along with a stable structure was determined for polyvinyl butyral nanofiber prepared under the optimum conditions. An aligned polyvinyl butyral nanoweb was applied on the mid-layer of glass-phenolic laminated composites as an interlaminar reinforcement. The fracture behavior of the laminates was determined by end-notched flexure tests. Excellent toughening property which was observed for the aligned polyvinyl butyral nanofibers caused the mode-II fracture toughness and its maximum force to increase by 25.2 and 40.8%, respectively.

Novel and simple method to synthesize donut-like TiO2 with photocatalytic activity

This paper presents a novel and simple method to fabricate donut-like TiO2 with efficient photocatalytic activity. Donut-like TiO2 was successfully prepared via electrospraying technique using a low molecular weight polyvinyl pyrrolidone (PVP) polymer. X-ray diffraction measurements show that donut-like TiO2 maintains a pure anatase structure. A transmission electron microscopy image reveals hollow donut-like TiO2. The effects of applied voltage parameter on energy gap, atomic force microscopy micrographs, field emission scanning electron microscopy pictures, and photoluminescence spectra are examined. The photocatalytic properties of donut-like TiO2 were evaluated with photocatalytic degradation of methylene blue (MB) in water under UV light irradiation. Donut-like TiO2 exhibits an efficient photocatalytic activity that reaches 67% after the degradation of MB in aqueous solution for 200min.

Statistically optimized fast dissolving microneedle transdermal patch of meloxicam: A patient friendly approach to manage arthritis

IntroductionThe long term administration of Meloxicam for the management of arthritis, a chronic disorder, results in gastrointestinal disturbances leading to poor patient compliance. Considering the favorable molecular weight, therapeutic dose, biological half-life and log P value of meloxicam for transdermal delivery, its fast dissolving microneedle patch, with an ability to breach the stratum corneum and efficiently deliver the cargo to deeper skin layers, were developed. MethodsMicroneedle patch of low molecular weight polyvinyl alcohol and polyvinylpyrrolidone was prepared using Polydimethylsiloxane micromolds. The ratio of polyvinyl alcohol to polyvinyl pyrrolidone and solid content of matrix solution was optimized to achieve maximum needle strength. The optimized batch was extensively evaluated for in vitro dissolution, drug release, stability, ex vivo skin permeation/deposition, histopathology and in vivo pharmacodynamic study. ResultsThe patch containing 9:1 polyvinyl alcohol to polyvinylpyrrolidone ratio with 50% solid content had shown maximum axial needle fracture force (0.9N) suitable for penetrating the skin. The optimized batch was found to be fast dissolving and released almost 100% drug in 60min following dissolution controlled kinetics. The formulation showed a significant drug deposition within skin (63.37%) and an improved transdermal flux (1.60μg/cm2/h) with a 2.58 fold enhancement in permeation as compared to plain drug solution. The formulation showed a comparable anti-inflammatory activity in rats when compared to its existing approved marketed oral tablet. Histopathology and stability evaluations demonstrated acceptable safety and shelf-life of the developed formulation. ConclusionThe successful verification of safety, efficacy and stability of microneedle patch advocated the suitability of the formulation for transdermal use.

Production of Laccase by Cochliobolus sp. Isolated from Plastic Dumped Soils and Their Ability to Degrade Low Molecular Weight PVC.

One of the utmost man-made problems faced today has been the ever-increasing plastic waste filling the world. It accounts for an estimated 20–30% (by volume) of municipal solid waste in landfill sites worldwide. Research on plastic biodegradation has been steadily growing over the past four decades. Several fungi have been identified that produce enzymes capable of plastic degradation in various laboratory conditions. This paper presents a study that determined the ability of fungi to degrade low molecular weight polyvinyl chloride (PVC) by the enzyme laccase. We have isolated a fungal species, Cochliobolus sp., from plastic dumped soils and they were cultured on Czapek Dox Agar slants at 30°C. The effectiveness of this fungal species on the degradation of commercial low molecular weight polyvinyl chloride (PVC) was studied under laboratory conditions. Significant differences were observed from the FTIR, GC-MS, and SEM results in between control and Cochliobolus sp. treated PVC.

Preparation and catalytic application of sulfonated PVA-Zr-pillared clay nanocomposite materials towards one pot synthesis of hexahydropyrimidines

A series of sulfonated polyvinyl alcohol-Zr-pillared clay nanocomposites were synthesized. A low molecular weight polyvinyl alcohol (PVA) was sulfonated using chlorosulfonic acid. The sulfonated PVA was intercalated inside the parent clay and Zr-pillared clay (Zr-P) matrix. In an alternative approach, the polyvinyl alcohol was initially intercalated into the clay and Zr-P structure followed by in-situ sulfonation inside the clay matrix. The composite materials were characterized using XRD, FTIR, Raman, UV–vis and FE-SEM analytical techniques. Expansion in clay interlayer due to insertion of the polymeric species and the Zr-pillars was observed from XRD study. FTIR and UV–vis study revealed presence of hydrated sulfonic acid clusters in the composite materials. The clay sheets were largely present in an exfoliated state in the clay-polymer composite materials. Insertion of the Zr-pillar imparts structural rigidity and consequent changes in the morphological features. The catalytic activity of the Zr-pillared clay-sulfonated polyvinyl alcohol composite materials has been investigated for synthesis of hexahydropyrimidines by multicomponent condensation of substituted aniline, formaldehyde and β-dicarbonyl compounds. The composite materials were found to be highly active for synthesis of structurally diverse hexahydropyrimidines in high yield and purity.

Dielectric properties and analysis of H-bonded interaction study in complex systems of binary and ternary mixtures of polyvinyl alcohol with water and DMSO

The dielectric relaxation properties and dipole ordering of binary mixtures of low molecular weight Poly Vinyl alcohol (PVA) with water (WAT) and ternary mixtures of PVA+WAT with Dimethylsulfoxide (DMSO) of different concentration have been measured at 298K using Time Domain Reflectometry (TDR) technique. The measured values of permittivity (ϵ′), dielectric loss (ϵ″), static dielectric constant (ϵ0) and high frequency limiting dielectric constant (ϵ∞) have been measured in frequencies 10MHz to 30GHz and used to determine the values of molecular relaxation time (τ), and excesses permittivity (ϵE) of the different composition of binary and ternary mixtures. The formation of H-bonded complexes between PVA and WAT molecules increases the number of dipoles of binary mixtures. The PVA+WAT mixture forms the strongest complexes corresponding to the various concentrations. The ternary mixtures indicate the existence of heterogeneous species of different characteristics and molecular interactions in dilute solutions. The ϵE values of the ternary mixtures confirm the increase in dipole number. This contributes the raise in dielectric constant values and formation of the ternary complexes. The ionic conductivity (σ) and activation energy (ΔF) justify that the electronic polarization is influenced by heterogeneous H-bond of complexes of both binary and ternary systems. The Kirkwood correlation factor (gf) and effective Kirkwood correlation factor (geff) indicates the dipole ordering of the binary and ternary mixtures. The comparative values of various binary and ternary mixtures of different composition suggest that the nature of heterogeneous interaction varies with the solvent. Variations of the constituent compositions in the binary and ternary mixture also identified.

Method development for compositional analysis of low molecular weight poly(vinyl acetate) by matrix-assisted/laser desorption-mass spectrometry and its application to analysis of chewing gum

The influence of the sample preparation parameters (the choice of the solvent and of the matrix:analyte ratio) was investigated and optimal conditions were established for MALDI mass spectrometry analysis of the pristine low molecular weight polyvinyl acetate (PVAc). It was demonstrated that comparison of polymer’s and solvent’s Hansen solubility parameters could be used as a guide when choosing the solvent for MALDI sample preparation. The highest intensity PVAc signals were obtained when ethyl acetate was used as a solvent along with the lowest matrix–analyte ratio (2,5-dihydroxybenzoic acid was used as a matrix in all experiments). The structure of the PVAc was established with high accuracy using the matrix-assisted laser desorption/ionization-Fourier transform mass spectrometry (MALDI-FTMS) analysis. It was demonstrated that PVAc undergoes unimolecular decomposition by losing acetic acid molecules from its backbone under the conditions of FTMS measurements. Number and weight average molecular weights as well as polydispersity indices were determined with both MALDI-TOF and MALDI-FTMS methods. The sample preparation protocol developed was applied to the analysis of a chewing gum and the molecular weight and structure of the polyvinyl acetate present in the sample were established. Thus, it was shown that optimized MALDI mass spectrometry could be used successfully for characterization of polyvinyl acetate in commercially available chewing gum.

Highly sensitive and spatially resolved polyvinyl alcohol/acrylamide photopolymer for real-time holographic applications

By employing low molecular-weight polyvinyl alcohol (PVA) as binder, the spatial resolution of a red-sensitive PVA/acrylamide based photopolymer are improved from 1000 lines/mm to 3000 lines/mm. By increasing the ambient temperature during the holographic recording, the photosensitivity of photopolymer is also increased about 5 times. The optimized photopolymer system has high capacity such as high photosensitivity (8 mJ/cm(2)), high spatial resolution (over 3000 lines/mm) and high diffraction efficiency (over 94%). To our knowledge, its holographic recording performance is the best of ever reported PVA/acrylamide based photopolymer systems. It has good application prospects in real-time holographic interferometry, holographic storage and holographic display.

In vitromicrobiological evaluation of polyvinyl alcohol-based ocular inserts of Ciprofloxacin hydrochloride

Soluble inserts of ciprofloxacin hydrochloride using high and low molecular weight polyvinyl alcohol alone and in various combinations were fabricated by a casting technique. The in vitro drug release from the prepared inserts was studied using a continuous flow-through model, developed in our laboratory. The antimicrobial efficacies of the prepared inserts against common ocular pathogens, viz., Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853, were evaluated using a modified in vitro microbiological model. Ciprofloxacin hydrochloride release from the inserts followed matrix diffusion kinetics showing an anomalous release mechanism (erosion-controlled) based on the calculated release exponent (n) values. Drug release increased with an increase in the proportion of high molecular weight polyvinyl alcohol in the inserts. The in vitro microbiological model demonstrated the effectiveness of the inserts against the two microorganisms. Further, the results of the in vitro release studies correlated well with that of the antimicrobial studies.

Characterization of Low-molecular-weight Polyvinyl Alcohol for Restoration Purposes

Low molecular weight polyvinyl alcohol, used in the paper industry as a pigment coating adhesive, was tested as a re-sizing agent used in paper restoration to strengthen decayed papers. All of the tests (pH, degree of polymerisation, folding endurance, tensile strength, opacity, blue reflectance and reversibility) done after accelerated aging in different ambient conditions and for various lenghts of time resulted in very good results for the tested type of polyvinyl alcohol for the intended purpose

Characterization of Low Molecular Weight Polyvinyl Acetate

Characterization of Low Molecular Weight Polyvinyl Acetate

Reasons for the crystallinity of low molecular weight polyvinyl chloride

Reasons for the crystallinity of low molecular weight polyvinyl chloride