Studies on the Hydration Behavior of Polyvinyl Alcohol in Aqueous Solution: A Kinetic Approach through the Hydrolysis of Benzocaine

The present work investigates the structural and dynamical features of Polyvinyl alcohol (PVA) and surfactant–PVA system through the change in the rate of hydrolysis of benzocaine. The UV–Vis spectra of benzocaine showed that the absorbance values at λ_max (284 nm) increased with the increase in PVA. The rate of hydrolysis decreased in the dilute- and high-concentration regions of PVA, whereas it remains unchanged in the mid-concentration range of PVA, known as the polymer–polymer interaction region. These observations correspond to the structural changes in PVA with the increase in PVA concentration in aqueous solution. The aggregation behavior of PVA was further studied using transmission electron microscopy micrographs. The rate constant for the hydrolysis of benzocaine showed peaked behavior with the increase in [CTABr] in the CTABr-PVA mixed system. The sodium dodecyl sulphate (SDS) molecules modify the PVA chains into a more compact form, and so, the hydration number around PVA is decreased. Consequently, the less hydrophilic benzocaine entangles with SDS-PVA, whereas OH^– ions aggregate into the aqueous pseudophase, resulting in a decrease in the rate of hydrolysis in the SDS–PVA mixed medium. The calculated value of binding constant increased with the increase in PVA in both CTABr-PVA and SDS-PVA mixed systems.     

Partition of α-lactoalbumin and β-lactoglobulin from goat milk whey utilizing aqueous biphasic systems

This paper presents a study of α-lactoalbumin and β-lactoglobulin proteins partition from goat milk whey in-nature, utilizing aqueous biphasic systems comprised of polymers (polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone), potassium phosphate, and water. The systems were evaluated at 25°C and pH 7.0. The influence of the polymer type, of the polymer molecular weight, and the polymer mass percentage on the partition coefficient of these proteins was assessed. Among the analyzed polymers, the polyethylene glycol (1500) was more indicated. The results showed that the separation technique by aqueous biphasic systems are applicable indicating high efficiency in the whey proteins separation process.     

Conjugated polymers with anionic dyes: Synthesis,properties, and sensing ability for nucleosides,DNA, and BSA

The reaction of N-(2,4-dinitrophenyl)pyridinium chloride (salt[Cl⁻]) with sodium salts of anionic dyes, such as acid red 52 (AR52), acid violet 49 (AV49), and coomassie brilliant blue G-250 (CBBG250) involves an anion exchange between the chloride anion of salt(Cl⁻) and sulfonium anion of the dyes, resulting in the generation of novel Zincke salts, namely, salt(AR52), salt(AV49), and salt(CBBG250), respectively. Reactions of salt(AR52), salt(AV49), and salt(CBBG250) with piperazine in the absence of catalysts resulted in the opening of the pyridinium ring to yield ionic polymers comprising units of 5-piperazinium-2,4-dienylideneammonium and the corresponding dye anion, namely polymer(AR52), polymer(AV49), and polymer(SBBG250), respectively. The corresponding model compounds for the polymers were also synthesized by reacting salt(AR52), salt(AV49), and salt(CBBG250) with piperidine. Polymer(AV49) and polymer(SBBG250) were found to be suitable for the detection of nucleosides, DNA, and proteins, realized by monitoring the changes in their UV–vis absorption spectra, arising from the anionic dyes within the polymers. The polymers and the model compounds were electrochemically oxidized in solution.     

Effect of the type of polymer functional groups on the structure of its film formed on the alumina surface – Suspension stability

The effects of polymer functional group and solution pH on stability of colloidal Al₂O₃ water suspension were studied. Both the nonionic polymers: polyethylene glycol (PEG), polyethylene oxide (PEO) and the ionic ones: polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA) were used in the experiments. The following methods were applied: turbidimetry (stability measurements), spectrophotometry (determination of polymer adsorption), viscosimetry (thickness of polymer adsorption layer), potentiometric titration (solid surface charge density) and microelectrophoresis (potential zeta). It was shown that anionic polyacrylic acid is both the most effective stabilizer (at pH 9) and flocculant (at pH 3) of the alumina suspension. Its carboxyl groups have the greatest affinity for the surface active sites (the largest adsorption) of all functional groups present in the other examined polymers. The latter, i.e. hydroxyl (PEG, PEO, and PVA) and acetate (PVA) show a much lower affinity for the Al₂O₃ surface (negligible adsorption) and minimally affect the stability of the alumina-solution system.     

Adsorption of Anionic and Cationic Dyes from Aqueous Solution on Non-Calcined Mg-Al Layered Double Hydroxide: Experimental and Theoretical Study

Non-calcined Mg-Al layered double hydroxide (LDH) with Mg/Al molar ratio of 3:1 was synthesized using the co-precipitation method. Sorption of anionic (acid blue 25 - AB25, reactive blue 4 - RB4), and cationic (methylene blue - MB) dyes by Mg-Al LDH form aqueous solution was investigated. The effect of solution pH, initial concentration, and contact time were investigated by batch adsorption experiments. The adsorbed amount increases with decrease in pH solution for AB25 and RB4. The cationic dye (MB) solution was insensitive to pH variation and also exhibited a low performance in the kinetic equilibrium studies. While anionic dyes were almost completely extracted from the solution, 90% of the methylene blue remained in solution. The equilibrium data were well described using the Langmuir-Freundlich model for RB4, AB25, and MB dyes with maximum adsorption capacity of 328.90, 246.10, and 43.48 mg/g, respectively. Finally, the mechanism of adsorption involving the dyes and LDH was evaluated using the Monte Carlo approach in the NVT ensemble. The results suggest that molecular simulation can be used to preview quantitatively the dye uptake. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

Structural characterization of hydrophilic polymer blends/montmorillonite clay nanocomposites

The nanocomposite films comprising polymer blends of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO), and poly(ethylene glycol) (PEG) with montmorillonite (MMT) clay as nanofiller were prepared by aqueous solution casting method. The X‐ray diffraction studies of the PVA–x wt % MMT, (PVA–PVP)–x wt % MMT, (PVA–PEO)–x wt % MMT and (PVA–PEG)–x wt % MMT nanocomposites containing MMT concentrations x = 1, 2, 3, 5 and 10 wt % of the polymer weight were carried out in the angular range (2θ) of 3.8–30°. The values of MMT basal spacing d₀₀₁, expansion of clay gallery width W_cg, d‐spacing of polymer spherulite, crystallite size L and diffraction peak intensity I were determined for these nanocomposites. The values of structural parameters reveal that the linear chain PEO and PEG in the PVA blend based nanocomposites promote the amount of MMT intercalated structures, and these structures are found relatively higher for the (PVA–PEO)–x wt % MMT nanocomposites. It is observed that the presence of bulky ester‐side group in PVP backbone restricts its intercalation, whereas the adsorption behavior of PVP on the MMT nanosheets mainly results the MMT exfoliated structures in the (PVA–PVP)–x wt % MMT nanocomposites. The crystallinities of the PEO and PEG were found low due to their blending with PVA, which further decreased anomalously with the increase of MMT concentration in the nanocomposites. The decrease of polymer crystalline phase of these materials confirmed their suitability in preparation of novel solid polymer nanocomposite electrolytes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40617.     

Acid-treated Bentonite as filler in the development of novel composite PVA hydrogels

In this study, novel eco-friendly hydrogel adsorbents were synthesized based on poly(vinyl alcohol) (PVA) and different contents of an acid-treated bentonite (1–5 wt %). The hydrogels were prepared by freezing–thawing, which is a simple and nontoxic method. The materials were morphologically and thermally characterized by means of swelling assays, X-ray diffraction, scanning electron microscopy, dynamic scanning calorimetry, and thermogravimetric analysis in order to evaluate the effect of acid-treated bentonite loading. The composite hydrogels showed very distinct porous structure and thermal features in comparison to neat PVA as a consequence of the addition of the clay. Moreover, the performance of the obtained composite hydrogels was tested toward the adsorption of cationic (methylene blue) and anionic dyes (methyl red and methyl orange) from aqueous media. The presence of acid bentonite seems to be beneficial for improving the removal capacity of PVA-based hydrogels. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47663.     

Inhibition effect of some polymers on the corrosion of cadmium in a hydrochloric acid solution

The effects of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), sodium polyacrylate (NaPA), poly(ethylene glycol) (PEG), pectin (P), and carboxymethyl cellulose (CMC) on the corrosion of cadmium in a 0.5M hydrochloric acid (HCl) solution were studied with both electrochemical impedance spectroscopy and Tafel plot techniques. Measurements were carried out at cathodic, open‐circuit, and anodic potentials. All the investigated polymers had inhibitory effects on both the cathodic (except for NaPA, P, and CMC) and anodic processes, with a predominant anodic inhibiting action. However, NaPA, P, and CMC exhibited a slight cathodic inhibiting action only at higher polymer concentrations. This behavior may be attributed to the very weak adsorbability of the polymers on the cathodic sites. Because PVA and PEG had hydroxy groups, there could be bridging between the polymer and the surface, resulting in an inhibiting effect in the HCl solution. However, PVA had much greater adsorbability on the surface than PEG at the anodic potential. The adsorption of most of the polymers obeyed a Temkin adsorption isotherm, and this indicated indicating that the main process of inhibition was adsorption. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 866–871, 2003     

A molecularly imprinted polymer via a salicylaldiminato‐based cobalt(III) complex: A highly selective solid‐phase extractant for anionic reactive dyes

A novel molecularly imprinted polymer based on tert‐butyl acrylate (MIP‐BA) was fabricated with the assistance of a cobalt(III)‐based catalyst bearing an N‐salicylidene isopropylamine ligand [(SPA)₂CoCl]. After initiation with methyl aluminoxane, the catalyst system was found to be active toward the polymerization of tert‐butyl acrylate (t‐BA) in the presence of a polar template (Cibacron reactive red dye) and divinylbenzene (DVB) as a crosslinker. Polymerization experiments, including those of t‐BA, t‐BA, and DVB and t‐BA and dye, were also carried out. Isolated blank polymers and MIP‐BA were analyzed with a variety of techniques, including differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, infrared spectroscopy, nuclear magnetic resonance, and ultraviolet–visible spectroscopy. In general, the complex showed moderate polymerization activity and produced high‐molar‐mass poly(tert‐butyl acrylate); however, a decrease in the monomer conversion was observed upon the addition of the dye and/or the crosslinker. The effect of imprinting was obvious when the adsorption capacity of MIP‐BA measured at pH 6 for red dye (the imprinted molecule) was increased from 9.2 to 90.4 mg/g after imprinting. Competitive adsorption studies revealed that the dye‐imprinted polymer enabled the efficient uptake of red dye, even in the presence of blue and yellow dyes that had similar chemical structures to the imprinted molecule. The selectivity coefficients were 43 and 36 with respect to the blue and yellow dyes, respectively. The proposed polymerization procedure could be extended to other anionic polar reactive dyes and polar reactive polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Modeling the protein partitioning in aqueous polymer two-phase systems: influence of polymer concentration and molecular weight

Aqueous polymer two-phase system provides a powerful method for separation and purification of biomaterials. Among various factors, polymer concentration and polymer molecular weight are essential and have strong impact on the protein partitioning in these systems. Based on the modified Pitzer's model, a simple expression has been obtained for correlating protein partitioning in aqueous polymer two-phase systems with varying polymer concentration and different polymer molecular weights. Using only one group of parameters for each target protein, the partition coefficients of five proteins (lysozyme, chymotrypsinogen-A, bovine serum albumin, transferrin and catalase) in 16 sets of polyethylene glycol (PEG)/dextran systems were correlated. In addition, partition behavior of lactate dehydrogenase in PEG/hydroxypropyl starch systems were measured, correlated and partially predicted. A comparison of calculated and experimental data indicated that the model provides good correlation and prediction abilities on the protein partitioning in aqueous polymer two-phase systems with a wide range of polymer concentration and molecular weight.     

Effects of Inorganic Salts and Polymers on the Foam Performance of 1-Tetradecyl-3-methylimidazolium Bromide Aqueous Solution

The foaming performance of 1-tetradecyl-3-methylimidazolium bromide (C₁₄mimBr) aqueous solution, in the presence of polymers (PEG or PVA) or inorganic salts (NaBr, MgCl₂, NaNO₃, Na₂SO₄ or Na₃PO₄), was investigated at 25.0?°C by using the self-made apparatus and the conductivity method. The experimental results show that the foaming ability and foam stability of the ternary aqueous systems of C₁₄mimBr coexisting with PEG or PVA are stronger than those of the C₁₄mimBr solutions in the absence of a polymer, and both the efficiency of foaming ability and foam stability of the surfactant solutions are evidently enhanced with an increase in polymer concentration. However, the addition of inorganic salts can decrease the foaming ability and foam stability of C₁₄mimBr solution. Especially, the inorganic salts, with high valence state of the anion (SO₄ ^2? and PO₄ ^3?), are good antifoam agents which can remove and inhibit foam quickly. For the aqueous solution of the surfactant, the effect of temperature on foaming properties was also examined. The results show that both the foaming ability and stability of the foams of the surfactant solutions decrease with an increase in the temperature within the range from 25.0 to 45.0?°C.     

Effect of molecular architecture on the self-diffusion of polymers in aqueous systems: A comparison of linear, star, and dendritic poly(ethylene glycol)s

Star polymers with a hydrophobic cholane core and four poly(ethylene glycol) (PEG) arms, CA(EG_n)₄, have been synthesized by anionic polymerization. Pulsed-gradient spin-echo NMR spectroscopy was used to study the diffusion behavior of the star polymers, ranging from 1000 to 10,000 g/mol, in aqueous solutions and gels of poly(vinyl alcohol) (PVA) at 23 °C. The star polymers have a lower self-diffusion coefficient than linear PEGs at equivalent hydrodynamic radius. In water alone, the star polymers and their linear homologues have a similar diffusion behavior in the dilute regime, as demonstrated by the similar concentration dependence of the self-diffusion coefficients. In the semidilute regime, the star polymers tend to aggregate due to their amphiphilic properties, resulting in lower self-diffusion coefficients than those of linear PEGs. ¹H NMR T₁ measurements at 10-70 °C revealed that the PEG arms of the star polymers are more mobile than the core, suggesting the star polymers in solution have a conformation similar to that of poly(propylene imine) dendrimers.     

Thermal,structural, and optical properties of γ‐irradiated poly(vinyl alcohol)/poly(ethylene glycol) thin film

Poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) copolymer was prepared using casting technique. The obtained PVA/PEG thin films have been irradiated with gamma rays with doses ranging from 1.5 to 20 Gy. The resultant effect of gamma irradiation on the thermal properties of PVA/PEG has been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The onset temperature of decomposition T_o and activation energy of thermal decomposition E_a were calculated, results indicating that the PVA/PEG thin film decomposes in one main weight loss stage. Also, the gamma irradiation in dose range 4–12 Gy led to a more compact structure of PVA/PEG copolymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with gamma dose has been determined using DTA. The PVA/PEG thermograms were characterized by the appearance of an endothermic peak due to melting of crystalline phase. In addition, structural property studies using X‐ray diffraction and infrared spectroscopy were performed on both nonirradiated and irradiated samples. Furthermore, the transmission of the PVA/PEG samples and any color changes were studied. The color intensity (E was greatly increased with increasing the gamma dose and was accompanied by a significant increase in the blue and green color components. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A spectroscopic and modelling study of polymer/dye interactions†

A spectroscopic study has been made of the comparative effectiveness of nonionic, zwitterionic and cationic polymers in binding model dyes. Addition of polymer produces smaller changes in the UV–vis spectra than observed in micellar solutions. Upon binding to polymers, the measured pK_A values of the model dyes decrease. The results of modelling and spectroscopic studies of the interaction between the model arylazonaphthol dyes are discussed in this paper. Addition of anionic surfactants, e.g. SDS, below their critical micelle concentrations disrupts polymer/dye binding, resulting in relocation of model dye to new sites formed from polymer/surfactant interactions. These sites are more apolar and produce spectra similar to those in corresponding micelles but with higher dye pK_A values and binding affinities. For the previous paper in this series see page 140; for parts 1 and 2 see refs 1 and 2, respectively.     

Nanofiltration membranes based on poly(vinyl alcohol) and ionic polymers

Nanofiltration membranes based on poly(vinyl alcohol) (PVA) and ionic polymers, such as sodium alginate (SA) and chitosan, were prepared by casting the respective polymer solutions. The membranes prepared from PVA or PVA–ionic polymer blend were crosslinked in a isopropanol solution using glutaraldehyde as a crosslinking agent. The membranes were characterized with Fourier transform infrared spectroscopy and X‐ray diffractometry and swelling test. The membranes crosslinked through the acetal linkage formation between the  OH groups of PVA and the ionomer and glutaraldehyde appeared to be semicrystalline. To study the permeation properties, the membranes were tested with various feed solutions [sodium sulfate, sodium chloride, poly(ethylene glycol) with 600 g/mol of molecular weight (PEG 600), and isopropyl alcohol]. For example, the permeance and the solute rejection of the 1000 ppm sodium sulfate at 600 psi of upstream pressure through the PVA membrane were 0.55 m³/m² day and over 99%, respectively. The effects of the ionomers on the permeation properties of the PVA membranes were studied using the PVA–SA and PVA–chitosan blend membranes. The addition of small amount of ionic polymers (5 wt %) made the PVA membranes more effective for the organic solute rejection without decrease in their fluxes. The rejection ratios of the PEG 600 and isopropanol were increased substantially. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1755–1762, 1999     

Cationic polyelectrolytes,XII. PEG-precursor for water-soluble cationic polymers with tertiary n-atoms in the main chain

Water-soluble cationic polymers were obtained by polyaddition of poly(ethylene glycol) (PEG) diglycidylethers (M?_n of PEG were 396, 587, 1437 and 3554, resp.) with asymmetrical diamines such as N,N-dimethyl-1,3-diaminopropane and N,N-diethyl-1,3-diaminopropane. The cationic polymer properties depend on the PEG initial molecular weight and on the diamine reactivity too. PEG with M?_n = 396 had the best behaviour in these reactions. The polyelectrolyte feature of cationic polymers was emphasized both in dilute aqueous solutions and in 2M aqueous NaCl solutions. The polyelectrolyte behaviour in 2M aqueous NaCl solution is determined by the PEG chain presence.     

Characterization of poly(vinyl alcohol)/poly(ethylene glycol) hydrogels and PVA-derived hybrids by small-angle X-ray scattering and FTIR spectroscopy

The purpose of this study is to develop novel poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogel blends and PVA-derived organic-inorganic hybrid materials and perform nanostructural characterizations. PVA and PEG hydrogels were prepared by dissolving the polymer in aqueous solution, followed by addition of glutaraldehyde (GA) chemical crosslinker. Hybrids were synthesized by reacting PVA in aqueous solution with tetraethoxysilane (TEOS). PVA/TEOS were also modified in the nanometer-scale by crosslinking with GA during the synthesis reaction. Hydrogels and hybrids were characterized by using small-angle X-ray scattering synchrotron radiation (SAXS) and Fourier transform infrared spectroscopy (FTIR). Thin film samples were prepared for SAXS experiments. SAXS results have indicated different nano-ordered disperse phases for hydrogels made of PVA, PEG, PVA/GA, PVA/PEG. Also, PVA/TEOS and PVA/TEOS/GA hybrids have indicated different X-ray scattering patterns. FTIR spectra have showed major vibration bands associated with organic-inorganic chemical groups present in the hybrid nanocomposites PVA/TEOS and PVA/TEOS/GA. PVA/PEG hydrogels and PVA-derived hybrid materials were successfully produced with GA crosslinking in nanometer-scale network.     

Reentrant phase transition of poly(N‐isopropylacrylamide) gels in polymer solutions: Thermodynamic analysis

The swelling behavior of poly(N‐isopropylacrylamide) (PNIPA) gels in polymer solutions, particularly in aqueous solutions of poly(ethylene glycol)s, was investigated using the theory of equilibrium swelling. The volume of the PNIPA gel and the partition parameter of the macromolecules between the gel and the solution phases were calculated for various extents of the energetic interactions between the components. The simulation results were compared with the experimental data reported in the literature. It was shown that the PNIPA gel has a tendency to a reentrant phase transition in an aqueous solution of low molecular weight linear polymers. In such a transition, the gel first collapses, then reswells, if the linear polymer concentration is continuously varied. The necessary condition for the reentrant behavior of PNIPA gels was predicted in terms of the interaction parameters among the PNIPA network, the linear polymer, and water. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 801– 813, 2002     

Polymer–solute interactions in solid–liquid two‐phase partitioning bioreactors

BACKGROUND: Biphasic systems with immiscible solvents have been studied for in situ product removal, and have shown improvements in bioreactor performance, however, problems associated with solvent biocompatibility, bioavailability and operation have been identified. One alternative is the solid–liquid system in which polymer beads are used, absorbing and removing target compounds from the aqueous phase while maintaining equilibrium conditions. This work aims to identify polymer properties that may be important in polymer selection for selected biotransformation molecules including 2‐phenylethanol, cis‐1,3‐indandiol, iso‐butanol, succinic acid and 3‐hydroxybutyrolactone. RESULTS: Relatively hydrophobic compounds (e.g. 2‐phenylethanol) tend to be absorbed by polymers better than hydrophilic ones (e.g. iso‐butanol) based on partition coefficient tests; values as high as 80 were obtained for the former and < 3 for the latter. Owing to the presence of polar functional groups on these compounds, polar polymers such as Hytrel® performed better than non‐polar ones such as Kraton®. Crystallinity and intermolecular hydrogen‐bonding were also found to be important polymer properties. CONCLUSION: Polymers showed excellent results in absorbing hydrophobic compounds such as aromatic alcohols, and positive results in absorbing hydrophilic compounds but to a lesser extent. Grafting hydrophilic functional groups onto polymers may be a promising approach for extending polymer uptake capabilities and is currently being investigated. Copyright © 2009 Society of Chemical Industry     

Grafting onto carbon black by the reaction of reactive carbon black having acyl chloride group with several polymers

Summary Acyl chloride group introduced onto carbon black rapidly lost its activity by the moisture in air. However, the decrease of acyl chloride group content in vacuum was negligibly small. By the reaction of the acyl chloride group with several polymers having hydroxyl or amino group, such as polyethylene glycol (PEG), poly(vinyl alcohol)(PVA), and polyethyleneimine (PEI), these polymers were found to be effectively grafted onto carbon black; for instance, the grafting ratio of PEG (Mn=8.2×10³), PVA (Mn=2.2×10⁴), and PEI (Mn=2.0×10⁴) was 18.5%, 32.9%, and 45.8%, respectively. The number of polymer grafted onto carbon black decreased with an increase of its molecular weight.