Hydroxyl Groups Of Polyvinyl Alcohol Research Articles

Optical properties and structural characteristics of zinc oxidecerium oxide doped polyvinyl alcohol films

Abstract Influence of zinc oxide cerium oxide (ZnO Ce 2 O 3 ) nanoparticles on the structural characteristics and optical properties of polyvinyl alcohol (PVA) films have been investigated. The fabricated PVA/ZnO Ce 2 O 3 nanocomposite films have been characterized by UV–visible spectroscopy, photoluminescence spectroscopy, X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The UV–vis analysis reveals the interaction of ZnO Ce 2 O 3 nanoparticles through hydroxyl groups of PVA. Photoluminescence spectra shows intense emission peaks due to the presence of ZnO Ce 2 O 3 nanoparticles. Microwave irradiation analysis shows the effect of nanoparticles on the degradation profile of PVA. The band gap energy measured based on UV–vis analysis shows enhanced conductivity of PVA films. XRD analysis shows the effect of annealing temperature on the XRD patterns of PVA. DSC analysis shows reduction in percentage of crystallinity with an increase in annealing temperatures and nanoparticles concentration. Thermal analysis by TGA shows enhanced thermal stability for the nanocomposites as compared to the PVA matrix. The data generated from these investigations will support the PVA nanocomposites for possible applications in opto-electronic devices.

Synthesis of nanocrystalline LaMn0.5Fe0.5O3 powders via a PVA sol–gel route

Abstract LaMn 0.5 Fe 0.5 O 3 powders were synthesized via a sol–gel route based on polyvinyl alcohol (PVA). Differential thermal (DTA) and thermogravimetric (TG) analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) techniques were used to characterize precursors and derived oxide powders. The effect of the molar ratios of hydroxyl groups of PVA to metal ions (OH/M) on the formation of LaMn 0.5 Fe 0.5 O 3 was investigated. XRD analysis showed single-phase and well-crystallized LaMn 0.5 Fe 0.5 O 3 of around 25 nm diameters was synthesized from the OH/M=1.5 precursor at 600 °C. For the precursor with OH/M=0.75, phase pure LaMn 0.5 Fe 0.5 O 3 was not obtained even at 1000 °C and La(OH) 3 was observed as impurity phase. LaMn 0.5 Fe 0.5 O 3 ceramics sintered at 1300 °C showed a dielectric constant of 4300 at room temperature and 100 kHz.

Effect of high adhesive polyvinyl alcohol binder on the anodes of lithium ion batteries

High molecular weight (MW) polyvinyl alcohol (PVA) was synthesized by two-step polymerizations and employed as an anodic binder of lithium ion batteries (LIBs). Numerous hydroxyl groups in PVA formed strong hydrogen bonds with both active materials and the current collector. These strong hydrogen bonds led to an increase in the amount of binder covering the surface of active materials and significantly enhanced the adhesion strength of electrodes. The high MW PVA binder showed much better cyclic performance for silicon/carbon anodes than polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA) binders.

Synthesis of La 2NiO 4 via a PVA-based route

Single-phase La 2NiO 4 has been prepared using polyvinyl alcohol (PVA) as a complexing agent. Thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to characterize precursor and derived oxide powders. The particle size and morphologies of La 2NiO 4 crystallites were characterized by field emission scanning electron microscope (FSEM). The effect of the mol ratios of metal ion to hydroxyl groups in polyvinyl alcohol on the formation of La 2NiO 4 was investigated. XRD analysis showed that single-phase and well-crystallized La 2NiO 4 was obtained from precursor with M/OH = 1:3 at 900 °C. The La 2NiO 4 ceramics sintered at 1300 °C for 4 h exhibits an electrical conductivity of 42.5 Ω −1 cm −1 at room temperature.

Synthesis of Bi2Fe4O9 via PVA sol–gel route

Abstract Bi 2 Fe 4 O 9 powders were synthesized by a sol–gel process using polyvinyl alcohol (PVA) as a complexing agent. Differential scanning calorimetry (DSC), thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Field emission scanning electron microscope (FSEM) techniques were used to characterize precursor and derived oxide powders. The effect of the ratios of positively charged valences to hydroxyl groups of PVA (M n + /–OH) on the formation of Bi 2 Fe 4 O 9 was investigated. XRD analysis showed that single-phase Bi 2 Fe 4 O 9 was obtained from the M n + /–OH = 2:1 and M n + /–OH = 1:1 precursors at the temperature of 700 °C. For the precursor with M n + /–OH = 4:1, pure Bi 2 Fe 4 O 9 formed at the temperature of 800 °C. Bi 2 Fe 4 O 9 powders clacined at 700 °C from M n + /–OH = 2:1 precursor shows weak ferromagnetism.

Effects of PVA content on the synthesis of LaFeO3 via sol–gel route

LaFeO3 were synthesized via a sol–gel route based on polyvinyl alcohol (PVA). Differential scanning calorimetry (DSC), Thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM) techniques were used to characterize precursors and derived oxide powders. The effect of the ratios of positively charged valences to hydroxyl groups of PVA (Mn+/–OH) on the formation of LaFeO3 was investigated. XRD analysis showed that single-phase and well-crystallized LaFeO3 was obtained from the Mn+/–OH=4:1 molar ratio precursor at 700°C. For the precursor with Mn+/–OH=2:1, nanocrystalline LaFeO3 with average particle size of ∼50nm was formed directly in the charring procedure. With increase of PVA content to Mn+/–OH=1:1, phase pure LaFeO3 was obtained at 500°C.

Boron adsorption mechanism on polyvinyl alcohol

Recently, an increase in the use of boron compounds has led to an increase in boron emissions, and concern has grown regarding its detrimental effects on the human body. An adsorbent that adsorbs boron selectively has been developed as a countermeasure. Although certain commercially available boron selective adsorbents can be used to remove boron from aqueous solutions by utilizing the strong affinity between boron and hydroxyl groups, the adsorption capacity appears to be insufficient. So, we adopted polyvinyl alcohol (PVA), which contains many hydroxyl groups, as a model adsorbent. We investigated the boron adsorption characteristics of PVA, and then studied the relationship between the number of adsorption sites and actual adsorption amounts. We assessed the adsorption result by using adsorption site availability (ASA) as an indicator of the ratio of effectively functioning hydroxyl groups from the many hydroxyl groups in PVA. ASA was expressed as a percentage of the experimental equilibrium adsorbed amount in relation to the theoretical equilibrium adsorbed amount. We also compared the adsorption isotherms and ASA obtained with PVA, commercially available N-methylglucamine-type resin (CRB03 and CRB05) and the adsorbent we synthesized from polyallylamine (PAA) and glucose (PAA-Glu). Although PVA has many hydroxyl groups in a molecule, ASA analysis revealed that only 6% of the hydroxyl groups in PVA was used for boron adsorption. On the other hand, CRBs and PAA-Glu exhibited higher ASA values (about 15% and 35% respectively) and adsorption amounts, suggesting that the sterically congested adsorbent structure had a great influence on boron adsorption and ASA.

Low‐Temperature Synthesis of BiFeO3 via PVA Sol–Gel Route

Bismuth ferrite (BiFeO3) powders were synthesized by a sol–gel process using polyvinyl alcohol (PVA) as a complexing agent. Thermogravimetric, Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), and field‐emission scanning electron microscope techniques were used to characterize precursor and derived oxide powders. The effect of the ratios of positively charged valences to hydroxyl groups of PVA (Mn+/–OH) on the formation of BiFeO3 was investigated. XRD analysis showed that single‐phase and well‐crystallized BiFeO3 was obtained from the Mn+/–OH=2:1 precursor at a temperature as low as 400°C. For the precursor with Mn+/–OH=4:1, BiFeO3 formed only at the temperature of 600°C. With Mn+/–OH=1:1 and 1.5:1 precursor, pure BiFeO3 powder was not obtained. In present work, single‐phase BiFeO3 can be formed at lower temperature and less organics are required; furthermore, the process is simple and easy to control.

Crosslinking reaction of poly(vinyl alcohol) with glyoxal

Crosslinking reactions are one of the most commonly used techniques to improve physical properties of polyvinyl alcohol (PVA). Commonly used crosslinkers for these reactions are di-functional compounds, such as glutaraldehyde and glyoxal. The hydroxyl groups of PVA react with aldehydes via formation of acetal bonds hence corsslinking could take place. Quantitative analysis of glyoxal crosslined PVA will be described in this report. A convenient FTIR method has been established to analyze degree of crosslinking in PVA. Analysis by 1H NMR spectroscopy methods will also be described.

Mechanism of proton conductivity in polyvinyl alcohol-phenolsulfonic acid membranes from 1H and 13C NMR data

With line narrowing during magic angle spinning in solid-state NMR, molecular mobility and hydration in composite membranes based on polyvinyl alcohol (PVA) and phenol-2,4-disulfonic acid (PSA) were studied as functions of the ratio of the acidic and polymeric components, the degree of cross-linking in the polymeric matrix, and the moisture content. It is shown that at high relative humidity proton transport takes place by means of the network of hydrogen bonds, which are formed by the H+ counterions, sulfonate groups, and water molecules. At low moisture content, the hydroxyl groups in PVA play an active role in proton transport.

Development of potentially biodegradable polyamide‐6 and polyvinyl alcohol blends: Physico‐mechanical properties, thermal properties, and soil test

AbstractBlends of polyamide‐6 with 5, 7.5, 10, 15, and 20 wt % of polyvinyl alcohol (PVA) were prepared by the extruding in a corotating twin‐screw extruder. The extrudate strands were cut into pellets and injection‐molded to make test specimens. These specimens were tested for physico‐mechanical properties such as tensile strength, impact strength, density, water absorption, hardness, and thermal characteristics by differential scanning calorimetry, heat distortion temperature (HDT), vicat softening point (VSP), and melt flow index. The prepared blends show enhanced biodegradation, water absorption, and density, but it is observed that the introduction of PVA into the polyamide–6 matrix shows considerable reduction in tensile strength, impact strength, HDT, VSP, and hardness initially, but subsequent addition does not show significant reduction because of the enhanced interaction between amide groups of polyamide‐6 and hydroxyl groups of PVA. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2339–2346, 2005

CROSS LINKING OF POLYVINYLALCOHOL AND STARCH WITH POLYACROLEIN-CH(OH)SO<sub>3</sub>H

Air dried, chemically stable, powdery, polyacrolein was immersed into liquid SO2 at room temperature in order to obtain the chemically active polyacrolein-CH(OH)SO3H. After immersion for 24hrs, light brown powdery polyacrolein-CH(OH)SO3H was gained. This powder is easily soluble in water. The polyacrolein-CH(OH)SO3H was reacted with alcohols to form polyacrolein acetals, which was soluble at room temperature in several organic solvents, such as dimethyl formamide, dimethyl sulfoxide, dioxane and acetone. CH(OH)SO3H groups in polyacrolein reacted with hydroxyl groups in polyvinylalcohol and starch in the aqueous SO2 solution. Polyvinylalcohol film crosslinked with polyacrolein-CH(OH)SO3H swelled to some extent but did not dissolve in water. Furthermore, the crosslinked polyvinylalcohol film displayed high elastic recovery. 84% recovery was obtained from 35% stretch in water, and this value was retained after 10 times stress-strain repeating tests. The dynamic modulus and tan δ had a low dependency on temperature.