Preparation of copoly(vinyl alcohol–styrenesulfonic acid) resin and its catalytic activity on hydrolysis of carbohydrates. II. Two-step polymerization using tetraethylthiuram disulfide as an initiator

Copoly(vinyl alcohol–styrenesulfonic acid) resin was prepared by a two-step polymerization, consisting of a suspension polymerization of styrene containing divinylbenzene using tetraethylthiuram disulfide as an initiator and a subsequent block copolymerization of vinyl acetate to the crosslinked polystyrene obtained, followed by sulfonation and saponification. Some reaction conditions in the polymerization of styrene were investigated to obtain copolymer containing more vinyl alcohol units. The catalytic activity of the copolymer on the hydrolysis of dextrin was investigated and found to be increased with increasing amount of vinyl alcohol units and with a lowering degree of crosslinking of the copolymer. The maximum acceleration of rate obtained in the presence of the copolymer was about six times that in the presence of Amberlite 120B. Catalytic activity of the copolymer on hydrolysis of sucrose and methyl acetate were also investigated and found to be comparable each other and lower than that for dextrin. The difference between the activities for dextrin and for sucrose and methyl acetate increased with an increasing amount of vinyl alcohol units in the copolymer.     

Pervaporation separation of binary organic-aqueous liquid mixtures using crosslinked poly(vinyl alcohol) membranes. IV. Methanol–water mixtures

The pervaporation separation of methanol–water (M/W) mixtures was carried out using crosslinked poly(vinyl alcohol) (PVA) membranes with the low molecular weight of poly(acrylic acid) (PAA) as the crossinking agent. The PVA/PAA ratio in the crosslinked membrane was 90/10, 85/15, and 80/20 by weight. The operating temperatures were 50, 60, and 70°C, and the compositions of methanol–water mixtures to be separated were 70/30, 80/20, 90/10, and 95/5 (M/W) solutions. In all cases, the PVA/PAA = 80/20 membrane showed the best results. For M/W = 90/10 solution, the separation factor, α_w/m = 465, and the permeation rate, 0.109 kg/m²h, at 70°C were obtained using the PVA/PAA = 80/20 menbrane. The permeation rate and the separation factor for M/W = 95/5 solution showed 0.033 kg/m²h and α_w/m = 2650, respectively, when PVA/PAA = 80/20 membrane was used. © 1996 John Wiley & Sons, Inc.     

Preparation of poly(vinyl alcohol)-grafted ion exchange resin and its catalytic activity. I. Photo-induced graft copolymerization of vinyl acetate on ion exchange resin

Photo-induced graft copolymerization of vinyl acetate on sulfonic acid-type ion exchange resins was investigated. In the copolymerization on isopropylated resin, graft copolymers with graft ratios (mole ratio of monomer unit of grafts to that of the resin) of up to 0.18 were obtained, although in the copolymerization on the original resin graft copolymer was not obtained. It was found that the graft ratio showed a maximum with reaction time, and the maximum graft ratio increased with conversion of the resin from the Na salt to the Fe(III) salt. Poly(vinyl alcohol)-grafted resins were obtained with saponification of the poly(vinyl acetate)-grafted resins, and their catalytic activities on the hydrolysis of amylose were investigated. The catalytic activity of the resins was found to increase with increasing graft ratio at values above 0.10. In the present experiment, however, the maximum acceleration of the reaction was up to 1.5-fold that of the original resin because of limited graft ratio.     

Isothermal crystallization of poly(vinyl alcohol–co–ethylene)

Isothermal melt crystallization of poly(vinyl alcohol–co–ethylene) with different ethylene contents was studied in the temperature range of 140°C–160°C. A differential scanning calorimeter was used to follow the energy of the crystallization process. The results were analyzed by Avrami and Hoffman–Laurizten methods. The Avrami exponent was close to 2, indicating two‐dimensional growth with a linear growth rate and crystals nucleating athermally. The equilibrium melting temperature was determined by the Hoffman–Weeks method. The rate of crystallization depended on ethylene content and temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1071–1077, 2003     

Preparation of pH‐sensitive poly(vinyl alcohol‐g‐methacrylic acid) and poly(vinyl alcohol‐g‐acrylic acid) hydrogels by gamma ray irradiation and their insulin release behavior

A series of pH‐responsive hydrogels were studied as potential drug carriers for the protection of insulin from the acidic environment of the stomach before releasing in the small intestine. Hydrogels based on poly(vinyl alcohol) networks grafted with acrylic acid or methacrylic acid were prepared by a two‐step process. Poly(vinyl alcohol) hydrogels were prepared by gamma ray irradiation (50 kGy) and then followed by grafting either acrylic acid or methacrylic acid onto these poly(vinyl alcohol) hydrogels with subsequent irradiation (5–20 kGy). These graft hydrogels showed pH‐sensitive swelling behavior and were used as carriers for the controlled release of insulin. The in vitro release of insulin was observed for the insulin‐loaded hydrogels in a simulated intestinal fluid (pH 6.8) but not in a simulated gastric fluid (pH 1.2). The release behavior of insulin in vivo in a rat model confirmed the effectiveness of the oral delivery of insulin to control the level of glucose. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 636–643, 2004     

Synthesis and characterization of poly(2‐ethylaniline)–poly(styrenesulfonic acid) and poly(o‐phenetidine)–poly(styrenesulfonic acid) complexes

This research focuses on the synthesis of ethyl and ethoxy substituted polyaniline with poly(styrenesulfonic acid) comprising a poly(o‐phenetidine)–poly(styrenesulfonic acid) [P(O? P)‐PSSA] and poly(2‐ethylaniline)–poly(styrenesulfonic acid) [P(2‐E)‐PSSA]. The complexes P(O? P)‐PSSA and P(2‐E)‐PSSA were prepared by chemical polymerization of monomer (o‐phenetidine, 2‐ethylaniline) with PSSA using an oxidant of ammonium persulfate in 1M HCl solution; polyaniline (PANI), poly(2‐ethylaniline) (P2E), poly(o‐pheneditine) (POP), and polyaniline‐poly(styrenesulfonic acid) (PANI‐PSSA) also were prepared by chemical polymerization to be the reference samples. The products were characterized by IR, VIS, EPR, water solubility, elemental analysis, conductivity, SEM, and TEM. IR spectral studies shown that the structure of P(2‐E)‐PSSA and P(O? P)‐PSSA complexes is similar to that of polyaniline. EPR and visible spectra indicate the formation of polarons. The morphology of the blend was investigated by measured SEM and TEM, indicating the conducting component and electrically conductive property of the polymer complexes. The pH value for deprotonation [pH ≥ 9.5 for P(2‐E)‐PSSA and pH ≥ 8.0 for P(O? P)‐PSSA] are higher than that of corresponding HCl salts, indicating an intimate interaction between polymer chains. Elemental analysis results show that P(O? P)‐PSSA has a nitrogen‐to‐sulfur ratio of ～52%, larger than that for P(2‐E)‐PSSA, ～41%. The conductivity of the complexes is around 10^?2S/cm, and the solubility of P(2‐E)‐PSSA and P(O? P)‐PSSA in water is 2.9 and 1.9 g/L, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1198–1205, 2005     

Separation characteristics of acetic acid–water mixtures using poly(vinyl alcohol‐g‐4‐vinyl pyridine) membranes by pervaporation and temperature difference evapomeation techniques

The separation of acetic acid–water mixtures was carried out using pervaporation (PV) and temperature difference evapomeation (TDEV) methods. For the separation process, 4‐vinyl pyridine was grafted on poly(vinyl alcohol). Membranes were prepared from the graft‐copolymer by casting method and crosslinked by heat treatment. The effects of feed composition on the separation characteristics were studied and the performances of the separation methods were compared. Permeation rates were found to be high in PV whereas separation factors were high in TDEV method. Membranes gave permeation rates of 0.1–3.0 kg/m²h and separation factors of 2.0–61.0 depending on the composition of the feed mixture and the method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1385–1394, 2006     

Separation characteristics of acetic acid–water mixtures by using poly(vinyl alcohol‐g‐4‐vinyl pyridine) membranes by pervaporation and temperature difference evapomeation techniques

The separation of acetic acid–water mixtures was carried by using pervaporation (PV) and temperature difference evapomeation (TDEV) methods. For the separation process 4‐vinyl pyridine was grafted on poly(vinyl alcohol). Membranes were prepared from the graft‐copolymer by casting method and crosslinked by heat treatment. The effect of feed composition on the separation characteristics was studied and the performances of the separation methods were compared. Permeation rates obtained in PV were found to be high, whereas separation factors were high in TDEV method. Membranes gave permeation rates of 0.1–3.0 kg/(m² h) and separation factors of 2.0–61.0, depending on the composition of the feed mixture and the method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2030–2039, 2006     

Separation of ethylene glycol–water mixtures with composite poly(vinyl alcohol)–polypropylene membranes

Composite membranes consisting of a crosslinked poly(vinyl alcohol)(PVA) active layer on top of a porous polypropylene (PP) support were prepared with glutaraldehyde as a crosslinking reagent. The degree of crosslinking and the thickness of the active layer were determined with attenuated total reflection–Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The membranes were used in the pervaporation dehydration of ethylene glycol (EG)–water mixtures. The effects of the crosslinker content and operational conditions, including feed EG concentration and operating temperature, on the permeation flux and selectivity of the PVA–PP composite membranes were investigated. We observed that the dehydration of a 80 wt % EG mixture at temperature of 60°C, a feed flow rate of 1.5 L/min, and a vacuum pressure of 10 mmHg could be effectively performed, and a moderate permeation flux and a high separation factor were obtained, that is, 0.91 kg m⁻² h⁻¹ and 1021, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pervaporation separation of isopropanol–water mixtures using mixed matrix blend membranes of poly(vinyl alcohol)/poly(vinyl pyrrolidone) loaded with phosphomolybdic acid

Mixed matrix membranes of poly(vinyl alcohol) and poly(vinyl pyrrilidone) blends were prepared by loading with phosphomolybdic acid (PMA) and their pervaporation (PV) properties were investigated for the PV separation of isopropanol. Membrane performance shown a dependence on the extent of PMA loading. The 4 wt % PMA‐loaded blend membrane had the highest separation factor of 29991, which declined considerably at higher loading. The flux of 4 wt % PMA‐loaded membrane was lower than that of nascent blend membrane. Feed water composition and temperature influenced the PV performance. Solubility selectivity was higher than diffusion selectivity. Degree of swelling was smaller after PMA loading exhibiting better separation ability. The PV results were analyzed using the Flory‐Huggins theory and sorption was dominated by Langmuir's mode. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrospinning of poly(vinyl alcohol) and poly(4‐styrenesulfonic acid) for fuel cell applications

Electrospun fibers of poly(vinyl alcohol) (PVA) and PVA/poly(4‐styrenesulfonic acid) (PSSA) were obtained. By varying PVA to PSSA weight ratios, various fiber sizes and shapes were observed. The fiber diameters ranged from 176 to 766 nm, and the largest fibers were obtained from 15 wt % aqueous PVA solution. The effect of solution viscosity on fiber morphology was discussed. The presence of PSSA in electrospun fibers was confirmed by Fourier Transform Infrared spectroscopy. The PVA fibers were thermally stable up to 250°C, and the PVA/PSSA fibers were stable up to approximately 150°C. The water stability of the fibers was improved by heat‐treatment at 120°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Permeation and separation characteristics of alcohol–water mixtures through poly(dimethyl siloxane) membrane by pervaporation and evapomeation

Permeation and separation characteristics for aqueous alcoholic solutions such as methanol/water, ethanol/water and 1-propanol/water were studied using a poly(dimethyl siloxane) membrane by pervaporation and evapomeation. Poly(dimethyl siloxane) membrane preferentially permeated alcohol from aqueous alcoholic solutions in both methods. The concentration of alcohol in the permeate by evapomeation was higher than that by pervaporation. However, the permeation rate for the former method was smaller than that for the latter method. In evapomeation with a temperature difference between the feed solution and the membrane surroundings, when the temperature of the membrane surroundings was kept constant and the temperature of the feed solution was raised, both the permeation rate and the permselectivity for ethanol increased with increasing temperature of the feed solution. On the other hand, as the temperature of the feed solution was kept constant and the temperature of the membrane surroundings was changed, the permeation rate decreased, but the permselectivity for ethanol increased remarkably with dropping temperature in the membrane surrounding. Under permeation conditions of a feed solution of 40°C and a membrane surrounding temperature of ?30°C in evapomeation, an aqueous solution of 10 wt % ethanol in the feed was concentrated to about 90 wt % in the permeate. The permselectivity for alcohol was in the order of methanol <ethanol <1-propanol. The above permeation and separation characteristics are discussed from the viewpoint of the physicochemical properties of the poly(dimethyl siloxane) membrane and the permeating molecules.     

Water‐absorptive blend fibers of copoly(acrylic acid–acrylamide) and poly(vinyl alcohol)

Through the addition of N‐hydroxymethyl acrylamide as a potential crosslinker, water‐absorptive blend fibers of copoly(acrylic acid–acrylamide) and poly(vinyl alcohol) with three‐dimensional network structures were prepared with heat‐crosslinking technology after fiber formation. Fourier transform infrared, scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry were used to analyze the structures and properties of the fibers. The tensile behavior and absorbent capacities of the fibers were also studied. The results showed that there were lots of chemical crosslinking points in the fibers, the compatibility of copoly(acrylic acid–acrylamide) and poly(vinyl alcohol) was perfect, and the tensile properties of the fibers could be improved effectively through stretching in a vapor bath. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3353–3357, 2006     

In vitro release of salicylic acid through poly(vinyl alcohol‐g‐itaconic acid) membranes

In this study, itaconic acid (IA) was grafted on poly(vinyl alcohol) (PVA) at two different grafting percentages, 7.0% (w/w) and 14.0% (w/w), and membranes were prepared from the grafted copolymer (PVA‐g‐IA). Performances of PVA and PVA‐g‐IA membranes for the transdermal release of salicylic acid (SA) at in vitro conditions were investigated by using 2.0 mg/mL SA solutions. Effect of the pH on the release of SA was studied by keeping pH of donor and acceptor solutions in a range of (2.1–7.4). Permeation studies were also carried on at different SA concentrations. Effect of temperature on the release of SA was investigated in the temperature range of (32–39) (±1)°C. Results showed that presence of IA decreased the release of SA from the PVA membranes and 73% SA was released at the end of 48 h at (32 ± 1)°C from the IA‐1 membranes. pH affected the release of SA through the grafted membranes and studies showed that release of SA was high with donor solution pH of 2.1. When the pH of donor and receiver solutions were kept at the same pH value, the overall SA% in permeate increased. Increase in concentration of SA decreased the release of SA for the studied membranes. Release of SA from PVA‐g‐IA membranes was temperature sensitive and increase in temperature from (32 ± 1)°C to (39 ± 1)°C increased the release percentage of SA by 24% (w/w). The overall activation energy for the permeation of SA through IA‐1 membrane was found to be 22.97 kJ/mol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Permeation and separation characteristics of acetic acid/water mixtures through poly(vinyl alcohol‐g‐itaconic acid) membranes by pervaporation,evapomeation, and temperature‐difference evapomeation

In this study, itaconic acid (IA) was grafted onto poly(vinyl alcohol) (PVA) with cerium(IV) ammonium nitrate as an initiator at 45°C. The grafted PVA was characterized with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. IA‐grafted PVA membranes were prepared with a casting method, and the permeation and separation characteristics of acetic acid/water mixtures were investigated with pervaporation (PV), evapomeation (EV) and temperature‐difference evapomeation (TDEV) methods. The effects of the feed composition, operating temperature, and temperature of the membrane surroundings on the permeation rate and separation factor for the acetic acid/water mixtures were studied. The permeation rates in EV were lower than those in PV, whereas the separation factors were higher. With the TDEV method, the permeation rates decreased and the separation factors increased as the temperature of the membrane surroundings decreased. The prepared membranes were also tested in PV, EV, and TDEV to separate the various compositions of the acetic acid/water mixtures (20–90 wt % acetic acid) at 40°C. The highest separation factor, 686, was obtained in TDEV with a 90 wt % acetic acid concentration in the feed. The activation energies of permeation in PV and EV were calculated to be 8.5 and 10.2 kcal/mol, respectively, for a 20 wt % acetic acid solution. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2322–2333, 2004     

Thermal behavior of poly(acrylic acid)–poly(vinyl pyrrolidone) and poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

Thermal analysis (TGA and DTA) of samples of PAA, PVP, PAA–PVP complexes, containing different weight fractions of PAA and ternary polymer–metal–polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl₃, NiCl₂, and Ni(NO₃)₂ on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA–PVP complex containing FeCl₃, NiCl₂, and Ni(NO₃)₂ showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA–PVP complex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4049–4057, 2006     

Modification of poly(vinyl alcohol) membranes using sulfur-succinic acid and its application to pervaporation separation of water–alcohol mixtures

For the purposes of the water-selective membrane material development for pervaporation separation, we crosslinked poly(vinyl alcohol) (PVA) with sulfur-succinic acid (SSA), which contains —SO₃OH, by heat treatment and investigated the effect of the crosslinking density on the separation of water–alcohol mixtures by pervaporation technique. The crosslinking reaction between PVA and SSA was characterized through Fourier transform infrared spectroscopy and differential scanning calorimetry tests by varying the amount of the crosslinking agent, the reaction temperature, and the swelling measurements of each pure component. The separation performance of the water–methanol mixture is not good due to the existence of sulfonic acid, hydrophilic group, in the crosslinking agent. However, for the water–ethanol mixture, the flux of 0.291 kg/m²h and the separation factor of 171 were obtained at 70°C when PVA-crosslinked membrane containing 7 wt % SSA was used. The same membrane also showed flux of 0.206 kg/m²h and a separation factor of 1969 at the same operating temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1717–1723, 1998     

O2 and N2 gas permselectivity of alternating copoly(vinylidene cyanide–vinyl acetate)

The sorption and permeation of oxygen and nitrogen in and through alternating copoly(vinylidene cyanide–vinyl acetate) [copoly(VDCN–VAc)] (T_g = 176°C) membranes annealed for different periods just below T_g, 160°C, were investigated over the pressure range from 100 to 1000 cmHg. The dual-mode sorption and mobility models were used to analyze the results. A sub-T_g annealing of copoly(VDCN–VAc) caused a slight decrease in the amount of sorption in the membranes. This decrease in the amount of oxygen and nitrogen sorption can be attributed to a decrease in the Langmuir sorption capacity term, C′_H, with increasing sub-T_g annealing period. The densification of copoly(VDCN–VAc) membranes caused simultaneously by the annealing remarkably reduced diffusion coefficients for both gases. The reduction in diffusion coefficients of Langmuir mode, D_H, for both gases was found to be larger than that of Henry's law mode, D_D. Furthermore, permselectivity of oxygen to nitrogen, the ratio of permeability coefficient of oxygen to nitrogen (P O₂/P N₂), reached to 11.8 for the copoly(VDCN–VAc) annealed for 30 h. Evidently the reduction of D_H and D_D for nitrogen with increasing annealing period was much larger than that for oxygen.     

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