Synthesis of poly(vinyl alcohol) phosphorylate–dicyandiamide–formaldehyde resin complex and its absorption of rare earth ions

Poly(vinyl alcohol) phosphorylate was prepared and its complex with dicyandiamide–formaldehyde resin was used for adsorption and separation of Sm³⁺, Nd³⁺, Gd³⁺, Ho³⁺, and Er³⁺ ions. The factors that affect the adsorption and separation of these ions on the polyacid–polybase complex, such as the acidity of the sample solution, adsorption capacity, and conditions of desorption, were investigated by means of spectrophotometry and inductively coupled plasma optical emission spectrometry. IR spectrometry and X‐ray photoelectric spectrometry were used to study the adsorption mechanism, and the probably coordination structure was given. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 962–968, 2002; DOI 10.1002/app.10197     

Graphene oxide/poly(vinyl alcohol) hydrogels with good tensile properties and reusable adsorption properties

Graphene oxide (GO)/poly(vinyl alcohol) (PVA) hydrogel (PGOH), which possesses good tensile and reusable absorption properties, has been prepared by the freezing–thawing method. The presence of GO visibly decreases the swelling ratio of PGOH and significantly enhances the tensile properties of PGOH due to the formation of hydrogen bonds between the GO and PVA. The maximum tensile strength and the equilibrium adsorption capacity of methylene blue (MB) of PGOH with 0.5?wt-% GO (PGOH-0.5) is found to be 15, being 4.1 times higher than that of pure PVA hydrogel. The spontaneous adsorption obeys the intraparticle diffusion kinetic model. In addition, PGOH-0.5 exhibits a promising cycling absorption performance. The 1st and 5th cycle of dye removal for PGOH-0.5 reached to 92 and 70%, respectively. Such enhancement in adsorption can be attributed to π–π stacking and strong electrostatic attraction between GO and MB.     

Swelling kinetics of modified poly(vinyl alcohol) hydrogels

Interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and monomer, N‐isopropylacrylamide (NIPAAm), diallyldimethylammonium chloride (DADMAC), or methacrylic acid (MAA) were prepared by using the sequential‐IPN method. The equilibrium swelling ratios of PVA/NIPAAm (VANP), PVA/DADMAC (VADC), and PVA/MAA (VAMA) are 412, 370, and 297 at 25°C, respectively. VANP had the highest swelling ratio in time‐dependent swelling behavior, whereas the swelling ratio of VAMA had the lowest. The n values of VANP, VADC, and VAMA are 0.72, 0.81, and 0.96, respectively. Transport of all IPN hydrogels is anomalous and their transport mechanisms are dominated by a combination of diffusion‐controlled and relaxation‐controlled systems. VAMA has the highest activation energy and VANP has the lowest activation energy. The values of all IPN hydrogels are from 4.66 to 16.49 kJ/mol, which proves that all IPN hydrogels are hydrophilic. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3310–3313, 2003     

Friction of double‐network hydrogels against glass substrate in poly(vinyl alcohol) aqueous solution

The frictional coefficient of biological joint cartilage is extremely low. For this, many researchers are looking to develop materials that are similar to those in nature. We prepared a poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate)/polyacrylamide double‐network hydrogel, and tested the friction of the hydrogel in poly(vinyl alcohol) (PVA) aqueous solution, which imitates a biological environment, against glass substrate. Results show that there is a transition sliding velocity in the friction test, which decreases with an increase in PVA solution concentration. At low sliding velocities, the frictional stress exhibits a minimum at a PVA concentration of 2c^*, where c^* is the overlap concentration. It is assumed that a separation layer of PVA has formed completely at this concentration, the thickness of which is calculated. In addition, the friction of the hydrogel is not sensitive to the normal pressure in PVA aqueous solution. © 2014 Society of Chemical Industry     

Water behavior of poly(vinyl alcohol)/poly(vinylpyrrolidone) interpenetrating polymer network hydrogels

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) and 1‐vinyl‐2‐pyrrolidone were prepared by radical polymerization with 2,2‐dimethoxy‐2‐phenylacetophenone as a photoinitiator and N,N′‐methylenebisacrylamide as a crosslinker. The IPN hydrogels were analyzed for the sorption behavior of water at 35°C and a relative humidity of 95% with a dynamic vapor sorption system, and water diffusion coefficients were calculated. Differential scanning calorimetry was used to quantitatively determine the amounts of freezing and nonfreezing water. The free‐water contents in the IPN hydrogel samples PV51, PV31, and PV11 were 74.40, 64.03, and 60.48% in pure water, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 24–27, 2003     

制备方法对GO/P(NIPAM-MA)水凝胶La3+吸附性能的影响

用冷冻聚合法和非冷冻聚合法制备了氧化石墨烯/聚(N-异丙基丙烯酰胺-顺丁烯二酸)(GO/P(NIPAM-MA))水凝胶,比较制备方法对GO/P(NIPAM-MA)水凝胶La³⁺吸附能力的影响,发现通过冷冻聚合法合成的水凝胶,具有更加优异的溶胀-退溶胀性能和吸附性能。NIPAM与MA摩尔比为10∶1的冷冻聚合法水凝胶,在370 mg/L的LaCl₃溶液中平衡吸附量为(29.87±0.073)mg/g,而相同条件下的非冷冻聚合法水凝胶平衡吸附量仅为(20.29±0.395)mg/g。冷冻聚合法水凝胶的Freundlich等温线拟合参数n值随着MA含量的增加呈线性增加,而非冷冻聚合法水凝胶增加幅度小于冷冻聚合法。经过5次吸附-解吸循环,冷冻聚合法水凝胶的形状和体积没有明显变化且吸附能力没有明显下降,而非冷冻聚合法水凝胶经过3次吸附-解吸循环就出现破碎,无法再使用。冷冻聚合法合成的GO/P(NIPAM-MA)水凝胶具有La³⁺平衡吸附量大、可重复使用等优点。     

Chitosan/poly(vinyl alcohol) hydrogels for amoxicillin release

Chitosan and poly(vinyl alcohol)-based hydrogel films were synthesized using tartaric acid as a crosslinking agent. The films denoted as CVT were then characterized using Fourier transform infrared, Nuclear magnetic resonance, X-ray diffraction, and scanning electron microscopy analysis. TG/DTG and DSC analysis were also carried out for the determination of thermal properties of hydrogel films. Swelling properties of these hydrogel films were investigated at two different pHs and temperatures. The swelling behaviors of all samples were increased in acidic medium, while decreased in alkaline medium. The enzymatic degradation of the hydrogels was studied using lysozyme, and degradation rates were found to be parallel with the swelling ratio for CVT hydrogel. The hydrogels were also used for the amoxicillin release in KCl/HCl and PBS buffer solutions. The release behaviors of CVT hydrogel films were slower and can be controlled as compared with commercial drug release systems. CVT hydrogel films may be more appropriate for controlled release of amoxicillin.     

Synthesis of copolymeric acrylamide/potassium acrylate hydrogels blended with poly(vinyl alcohol): Effect of crosslinking and the amount of poly(vinyl alcohol) on swelling behavior

A novel series of copolymeric acrylamide/potassium acrylate superabsorbents, blended with poly(vinyl alcohol), have been synthesized by using N, N′‐methylenebisacrylamide as a crosslinker and potassium persulphate (K₂S₂O₈) as an initiator. Swelling behavior of these hydrogels in water was investigated; and on the basis of swelling properties, the diffusional behavior of water into these hydrogel systems was analyzed. It was observed that with the increase of amount of poly(vinyl alcohol) or crosslinking, the swelling of the hydrogels decreased. The hydrogel synthesized by addition of 5% poly(vinyl alcohol) and 0.25% crosslinking showed maximum swelling of 54445%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1927–1931, 2005     

Silicon dioxide/poly(vinyl alcohol) composite hydrogels with high mechanical properties and low swellability

Poly(vinyl alcohol) (PVA) hydrogels with tissue-like viscoelasticity, excellent biocompatibility, and hydrophilicity have been considered as promising cartilage replacement materials. However, the low mechanical properties of pure PVA hydrogels limit their applications for bearing complicated loads. Herein, we report silicon dioxide (SiO₂)/PVA composite hydrogels fabricated by fabricated cyclically freezing/thawing the aqueous mixture of PVA and methyltrimethoxysilane (MTMS). MTMS hydrolyzes and forms SiO₂ particles in situ to reinforce PVA hydrogel. Meanwhile, silanol group condenses with hydroxyl groups of PVA and chemically bonds with PVA. The resulting SiO₂/PVA hydrogels exhibit much better mechanical properties than bare PVA hydrogel. In addition, the composite hydrogels keep very low swellable property. This prepared composite hydrogels are promising in a variety of biomedical applications such as artificial articular cartilage, drug delivery, and biosensors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46895.     

High‐efficiency recovery of rare earth ions by hydrolyzed poly(styrene‐co‐maleic anhydride)

Hydrolyzed poly(styrene‐co‐maleic anhydride) (PSMA) as a high‐efficiency adsorbent is used for recovering La³⁺, Eu³⁺, Tb³⁺, and Yb³⁺ from the simulate wastewater of bastnaesite leach liquor. The pseudo‐first‐order and pseudo‐second‐order models are used to fit adsorption data in the kinetic studies and the results show good correlation with the pseudo‐second‐order model. The Langmuir model is found to fit for the isotherm data of all the rare earth ions (RE³⁺) and the maximum adsorption capacity of hydrolyzed PSMA is 285.79, 301.92, 305.46, and 336.65 mg g^?1 at 298 K for La³⁺, Eu³⁺, Tb³⁺, and Yb³⁺, respectively. The adsorption could be conducted in at pH 6.0 and the equilibrium is fast established in 30 min. Competition from coexisting ions (Ca²⁺, Mg²⁺) was proved to be insignificant. Moreover, the spent adsorbent could be well regenerated and kept above 80% of adsorption efficiency at the end of the fifth cycle. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43676.     

Increasing the adsorption capacity and selectivity of poly(vinyl alcohol) hydrogels by an alternative imprinting technique

In this work, we report an innovative alternative imprinting method for obtaining chemically crosslinked poly(vinyl alcohol) hydrogels with β‐cyclodextrin as template. The materials present high affinity toward the template that imprinted them, revealed by the higher sorption yield of β‐cyclodextrin and higher selectivity factors of the imprinted material, by comparing with the nonimprinted reference. The imprinting kinetic and mechanism has been demonstrated by adsorption studies, binding isotherms and Scatchard analysis and is in good correlation with the information regarding the morphology of the materials, determined by fluorescence microscopy and atomic force microscopy. By using a novel fluorescence spectroscopy method of the starting polymer solution, the optimum amount of imprinting template could be determined. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42024.     

Swollen behavior of crosslinked network hydrogels based on poly(vinyl alcohol) and polydimethylsiloxane

Poly(vinyl alcohol) (PVA) was dissolved in the water to make a 10 wt % aqueous solution, and polydimethylsiloxane (PDMS) was mixed with 1 wt % 2,2‐dimethyl‐2‐phenylacetophenone (DMPAP) and 0.5 mol % methylenebisacrylamide (MBAAm) in isopropyl alcohol. This mixture was added to a PVA aqueous solution and heated at 90°C for 7 h. Various crosslinked networks were prepared at different molar ratios of PVA/PDMS (1:1, 1:3, and 3:1). The characterization of PVA/PDMS crosslinked networks was determined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), a universal testing machine (UTM), and the equilibrium water content (EWC). The DSC melting endotherms showed, at 219.49°C, a sharp endothermic peak of PVA, and PVA/PDMS crosslinked networks had melting peaks close to this point. The value of EWC increased with the content of PVA in the crosslinked networks, simultaneously depending on the temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 957–964, 2002     

Recovery of heavy metals from aqueous solution by using radiation crosslinked poly(vinyl alcohol)

Crosslinked poly(vinyl alcohol) (PVA) and PVA/acrylic acid hydrogels, prepared by γ‐irradiation, were used in the removal of heavy metals from aqueous solution. Comparative studies of the properties of the two hydrogels were made. The application of the prepared hydrogels as adsorbent materials for Cu²⁺, Co²⁺, and Ni²⁺ from aqueous solution was studied. The chemical and physical properties of the hydrogels, before and after adsorption of the heavy metal ions, were investigated by means of thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The efficiency of such hydrogels for the recovery of metal ions was determined by atomic absorption and UV spectroscopic analysis. The effect of changing pH on the metal uptake was also studied. It was found that the prepared hydrogels have a substantial ability to adsorb metal ions from their solution. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1649–1656, 2004     

Preparation and properties of chitosan/poly(vinyl alcohol) blend foams for copper adsorption

A new form of polymer blend, macroporous chitosan/poly(vinyl alcohol) (PVA) foams made by a starch expansion process, exhibits the functionalities of chitosan while avoiding its poor mechanical properties and chemical instabilities. The appropriate conditions for foaming are discussed using both insoluble and water‐soluble chitosan. The chitosan/PVA foams demonstrated interconnected and open‐cell structures with large pore size from tens to hundreds of micrometers and high porosities from 73.6 to 84.3%. Glutaraldehyde was employed to improve the retention of chitosan and copper adsorption of the chitosan/PVA foams. While it increased the retention of chitosan and the adsorption capacities, glutaraldehyde decreased the pore size and porosity. The macroporous structure of the chitosan/PVA foams indicates extensive application prospects in terms of the considerable adsorption of heavy metal ions. Copyright © 2006 Society of Chemical Industry     

Drug release behavior of electrical responsive poly(vinyl alcohol)/poly(acrylic acid) IPN hydrogels under an electric stimulus

The electrically modulated properties of interpenetrating polymer networks (IPN) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) under electric field were investigated for drug delivery systems. PVA/PAAc IPNs with various compositions were synthesized by a sequential method, that is, ultraviolet polymerization of AAc in the mixture of PVA and aqueous AAc monomer solution, followed by a freeze‐thawing process to prepare elastic hydrogels. The amount of loaded drug significantly increased with the content of PAAc containing ionizable groups in IPN. The amount of introduced ionic drug (cefazoline) was greater than that of the nonionic drug (theophylline). Release behaviors of drug molecules from negatively charged PVA/PAAc IPN were switched on and off in a pulsatile pattern depending on the applied electric stimulus. The released amount and the release rate of drug were influenced significantly by the applied voltage, ionic group contents in IPN, ionic properties of drug solute, and the ionic strength of release medium. In addition, the ionic properties of drug molecules dramatically affected release behaviors, thus the release of ionic drug was much more enhanced than that of the nonionic drug. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1752–1761, 1999     

Gellan/poly(vinyl alcohol) hydrogels: characterization and evaluation as delivery systems

Bioartificial polymeric materials in the form of hydrogels were prepared starting from blends of poly(vinyl alcohol) (PVOH) with gellan, using a procedure based on freeze–thawing cycles. The effect exerted by gellan on the properties of these materials was investigated. The materials were loaded with human growth hormone (GH) and the release of the drug was evaluated. The results obtained indicated that gellan favours the crystallization process of PVOH allowing the formation of a material with a more homogeneous and stable structure than that of pure PVOH hydrogels. Both the PVOH melting enthalpy and the elastic modulus increased with increasing gellan content in the hydrogels; in addition, the higher the gellan content in the samples, the lower was the amount of PVOH released. Gellan/PVOH hydrogels were able to release GH and the release was affected by the content of the biological component. The amount of GH released was within a physiological range. © 2001 Society of Chemical Industry     

Network characterization and swelling behavior of chemical hydrogels based on acid‐containing poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was modified with phthalic and succinic anhydrides to give vinyl alcohol–vinyl ester copolymers that contain carboxylate groups. These half‐esters were then crosslinked by using the poly‐ (ethylene glycol) (PEG) 400 diglycidylether. Low crosslinker/carboxylate ratios were used to obtain low degrees of crosslinking, so the capacity of the resulting hydrogel to absorb water was high. Water absorption was determined gravimetrically as a function of time at room temperature. The equilibrium swelling ratio and compressive modulus were characterized for all the resulting PVA hydrogels and related to the network structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3026–3031, 2003     

Removal of chromium (VI) from aqueous solutions using poly(4‐vinyl pyridine) beads

Sorption of hexavalent chromium ions from aqueous solution by poly 4‐vinyl pyridine [Poly(4‐VP)] was studied. The batch method was applied for adsorption processes. The effects of initial ion concentration, time, pH and temperature on adsorption were investigated. A treatment time of 60 min was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value for the process. The maximum adsorption performance was achieved at 86.7 mg g^?1 using 500 mg L^?1 Cr (VI) solutions. The process of adsorption of Cr (VI) was explained by Langmuir isotherm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2865–2870, 2006     

Transparent and semi-interpenetrating network P(vinyl alcohol)- P(Acrylic acid) hydrogels: pH responsive and electroactive application

ABSTRACT

In this paper, poly(vinyl alcohol)-poly(acrylic acid) based transparent semi-interpenetrating network (semi-IPN) hydrogels were synthesized by using a solvent mixture of dimethyl sulfoxide and deionized water via free radical polymerization and subsequent freeze-thaw technique. The formation of the semi-IPN hydrogels was conformed from FT-IR spectra. The acrylic acid concentration effect on the hydrogels was investigated in terms of transparency, crystalline structure and thermal stability by using UV-visible spectroscopy, X-ray diffraction and thermogravimetric analysis. Swelling behaviours of the semi-IPNPAP hydrogels were studied in deionized water and different pH solutions. The compression and electroactive behaviour was tested in fully hydrated stage by using compression test and by applying electrical voltage. The hydrogels showed displacements under the applying voltage and detailed experiment is illustrated.