Swelling of thermosensitive interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(acrylic acid)

The swelling behavior of interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) in water was studied. The PVA/PAA IPN gels were prepared by four synthetic methods. The swelling behaviors of these IPNs made by different methods were compared. The differences in swelling behaviors of samples are discussed on the basis of their structural and physical differences. © 1996 John Wiley & Sons, Inc.     

PH-induced structure change of poly(vinyl alcohol) hydrogel crosslinked with poly(acrylic acid)

The structure of the hydrogel of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was investigated by small angle X-ray scattering (SAXS) of synchrotron radiation. A physically crosslinked blend gel, which was prepared by repetitive freezing and thawing of an aqueous solution of PVA and PAA, could be chemically crosslinked by esterfication of PVA with PAA even in the hydrogel state. The chemical crosslinking induced the destruction of physical crosslinks into a folded structure, indicating that the chemical crosslinking proceeds at the sites around the physical crosslinks that contain PVA and PAA in much higher concentration than other portion of the gel. The pH-induced structure changes of the PVA hydrogels, chemically crosslinked with poly(acrylic acid) (PAA) were investigated by SAXS on the samples of various chemical crosslinking time. The gels were shrunk at pH4, and swollen at pH8. The results of SAXS showed, that the Porod slope changed with chemical crosslinking time from -3.5 to ?2.9 at pH4, and from ?2.9 to ?2.4 at pH8. The results suggest that a folded structure as a structural domain, which is characterized by fractally rough interface, tends to change into the structure that corresponds to percolation cluster, particularly at pH8. The gels immersed in pH8 showed a remarkable structure change accompanying swelling. The results revealed that a conformational change of PAA chains, induced by the pH change, can be explained by the presence of a structural domain in the gel network, where both PVA chains and PAA chains get entangled and partially form a interpenetrating polymer network(IPN).     

Poly(acrylic acid)–poly(vinyl alcohol) semi- and interpenetrating polymer network pervaporation membranes

A series of poly(acrylic acid) (PAA)–poly(vinyl alcoho) (PVA) semiinterpenetrating (SIPN) and interpenetrating (IPN) polymer network membranes were prepared by crosslinking PVA alone or by crosslinking both PVA and PAA. Glutaraldeyde and ethylene glycol were used as crosslinking agents for the PVA and PAA networks, respectively. The presence of PAA increases the permeability of the membranes while the presence of PVA improves their mechanical and film-forming properties. The mechanical properties of the membranes were investigated via tensile testing. These hydrophilic membranes are permselective to water from ethanol–water mixture and to ethanol from ethanol–benzene mixtures. The IPN membranes were employed for the former mixtures and the SPIN membranes for the latter, because the IPN ones provided too low permeation rates. The permeation rates and seperation factors were determined as functions of the IPN or SIPN composition, feed composition, and temperature. For the azeotropic ethanol–water mixture (95 wt % ethanol), the separation factor and permeation rate at 50°C of the PAA-PVA IPN membrane, containing 50 wt % PAA, were 50 and 260 g/m²h, respectively. For the ethanol–benzene mixture, the PAA–PVA SIPN membranes had separation factors between 1.4 and 1200 and permeation rates between 6 and 550 g/m²h, respectively, depending on the feed composition and temperature. © 1996 John Wiley & Sons, Inc.     

Electrical properties of sorbitol‐doped poly(vinyl alcohol)–poly(acrylamide‐co‐acrylic acid) polymer membranes

Solid polymer membranes from poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐acrylic acid) (PAA) with varying doping ratios of sorbitol were prepared using the solution casting method. The films were examined with Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and AC impedance spectroscopy. The impedance measurements showed that the ionic conductivity of PVA–PAA polymer membrane can be controlled by controlled doping of sorbitol within the polymer blends. The PVA–PAA–sorbitol membranes were found to exhibit excellent thermal properties and were stable for a wide temperature range (398–563K), which creates a possibility of using them as suitable polymers for device applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nanofibrillated cellulose,poly(vinyl alcohol), montmorillonite clay hybrid nanocomposites with superior barrier and thermomechanical properties

Nanocomposites of poly(vinyl alcohol) (PVA), nanofibrillated cellulose (NFC), and montmorillonite (MMT) clay were prepared via solvent casting. In addition to investigating the effect of clay loading, PVA matrices crosslinked with poly(acrylic acid) (PAA) were prepared and compared with linear (noncrosslinked) PVA nanocomposites. ¹³C NMR and infrared spectroscopy confirmed the presence of crosslinks. Scanning electron microscopy revealed effective NFC and MMT clay dispersion throughout the nanocomposites, while X‐ray diffraction highlighted the effectiveness of PAA to encourage clay dispersion. MMT clay provided a barrier against the diffusion of water and oxygen (molecules) through the nanocomposite films. Permeability and adsorption were further reduced by crosslinking, while oxygen barrier properties were remarkably enhanced at elevated relative humidities. Thermal stability of the PVA segments was strengthened by the presence of MMT clay and crosslinks. MMT clay–reinforced PVA and NFC within the films, increasing the Young's modulus, tensile strength, and glass transition temperature. Crosslinking further enhanced the thermomechanical properties by imparting physical restraints on polymer chain segments, providing elasticity, and ductility. The hybrid films were successfully reinforced at elevated humidities, with nanocomposites displaying enhanced storage moduli and near‐complete recovery. POLYM. COMPOS., 35:1117–1131, 2014. © 2013 Society of Plastics Engineers     

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     

Elaboration of ion‐exchange membranes with semi‐interpenetrating polymer networks containing poly(vinyl alcohol) as polymer matrix

Ion‐exchange membranes were prepared with semi‐interpenetrating networks (s‐IPNs) by mixing a film‐forming polymer, poly(vinyl alcohol) (PVA), for the crosslinked matrix and a polyelectrolyte for the specific ion‐exchange property. Poly(sodium styrenesulfonate) (PSSNa), poly(styrenesulfonic acid) (PSSH), and poly(acrylic acid) (PAA) were used as anionic polyelectrolytes. Polyethyleneimine (PEI), poly(1,1‐dimethyl‐3,5‐dimethylenepiperidinium chloride) (PDDPCl), and poly(diallyldimethylammonium chloride) (PDDMACl) were used as cationic polyelectrolytes. Membranes with PVA 60% and polyelectrolyte 40% showed the best compromise among mechanical, homogeneous, and ion‐exchange properties. Gaseous dibromoethane was used as a crosslinking agent to form the PVA network and for efficient entrapment of the polyelectrolyte in the membrane. The crosslinking time (tc) was optimized for each type of membrane and its influence was studied by thermogravimetric analysis of the sample and scanning electron microscopy observations. The best results (large ion‐exchange capacity and small swelling ratio) were obtained for PVA/PAA and PVA/PSSNa/PSSH membranes. Among anion‐exchange membranes, PVA/PEI gave the best permselectivity (low co‐ion leakage) and the highest ion‐exchange capacity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1572–1580, 2002; DOI 10.1002/app.10420     

微波驱动咪唑类聚离子液体/聚乙烯醇形状记忆材料

结合微波驱动原理、聚离子液体（PIL）及形状记忆聚合物的结构特性,目的是设计合成完全基于聚合物、能在微波驱动下快速回复的聚离子液体/聚乙烯醇（PVA）形状记忆复合材料。首先合成了乙烯基咪唑功能性离子液体单体（[ViEtIm][BF₄],ILM）,之后在含有戊二醛的PVA溶液中对ILM进行原位聚合生成PIL,将PIL引入到交联PVA中,形成聚乙烯基咪唑PIL/PVA形状聚合物复合材料（SMPC）。用核磁对ILM和PIL的结构进行了表征,证明了所合成目标化合物的结构准确性。介电性能测试结果显示PIL/PVA有较高的介电常数和介电损耗,当P[ViEtIm][BF₄]含量从0增加到30%时PIL/PVA复合材料的介电损耗因子呈增大趋势,可见PIL是一种有效的微波吸收介质。弯曲法测试结果表明该复合材料在微波驱动下具有很好的形状记忆效应,所有复合材料的形变固定率都接近100%且形变回复率都高达80%以上,且PIL的含量和微波输出功率的大小对材料回复率和回复时间有显著影响。140 W的微波足以驱动PIL/PVA SMPC发生回复,280 W下40 s内可以完成,微波功率增大到420 W时SMPC在20 s内可回复到起始形状。     

Preparation and swelling properties of semi‐IPN hydrogels based on chitosan‐g‐poly(acrylic acid) and phosphorylated polyvinyl alcohol

The phosphorylated poly(vinyl alcohol) (P‐PVA) samples with various substitution degrees were prepared through the esterification reaction of PVA and phosphoric acid. By using chitosan (CTS), acrylic acid (AA) and P‐PVA as raw materials, ammonium persulphate (APS) as an initiator and N,N‐methylenebisacrylamide as a crosslinker, the CTS‐g‐PAA/P‐PVA semi‐interpenetrated polymer network (IPN) ssuperabsorbent hydrogel was prepared in aqueous solution by the graft copolymerization of CTS and AA and followed by an interpenetrating and crosslinking of P‐PVA chains. The hydrogel was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) techniques, and the influence of reaction variables, such as the substitution degree and content of P‐PVA on water absorbency were also investigated. FTIR and DSC results confirmed that PAA had been grafted onto CTS backbone and revealed the existence of phase separation and the formation of semi‐IPN network structure. SEM observations indicate that the incorporation of P‐PVA induced highly porous structure, and P‐PVA was uniformly dispersed in the polymeric network. Swelling results showed that CTS‐g‐PAA/P‐PVA semi‐IPN superabsorbent hydrogel exhibited improved swelling capability (421 g·g^?1 in distilled water and 55 g·g^?1 in 0.9 wt % NaCl solution) and swelling rate compared with CTS‐g‐PAA/PVA hydrogel (301 g·g^?1 in distilled water and 47 g·g^?1 in 0.9 wt % NaCl solution) due to the phosphorylation of PVA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and swelling characteristics of pH and thermoresponsive interpenetrating polymer network hydrogel composed of poly(vinyl alcohol) and poly(acrylic acid)

The swelling behavior of novel pH- and temperature-sensitive interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) in water was investigated. The PVA/PAAc IPN hydrogels were synthesized by UV irradiation, followed by a repetitive freezing and thawing process by which PVA hydrogel networks were formed inside of cross-linked PAAc chains. The swelling behaviors of these IPNs were analyzed in buffer solution at various pH and temperature ranges. Swelling ratios of all IPNs were relatively high, and they showed reasonable sensitivity to both pH and temperature. Hydrogels showed both the positive and negative swelling behaviors depending on PAAc content. IPN46 showed the positive temperature-sensitive swelling behaviors and its stepwise changes in swelling ratio was about 1.8 and 2.0 obtained between 25 and 45°C at pH 7, and between pH 4 and 7 at 35°C, respectively. The positive temperature dependence is attributed to the formation and dissociation of hydrogen bonding complexes between PVA and PAAc. These IPNs are expected to show a pH- and temperature-sensitive drug release according to the stepwise behavior at this temperature region. © 1996 John Wiley & Sons, Inc.     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry     

A novel mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poly (ethylene glycol)

A new mucoadhesive polymer was prepared by template polymerization of acrylic acid in the presence of poly(ethylene glycol) (PEG). FTIR results indicated that a polymer complex was formed between poly(acrylic acid) (PAA) and PEG through hydrogen bonding. The hydrogen bonding in the PAA/PEG polymer complex was stronger than that in the PAA/PEG blend, and became stronger as the molecular weight of PEG increased. Glass transition temperatures (T_g) of PAA in the PAA/PEG polymer complexes was shifted to a lower temperature than that of PAA in the PAA/PEG blend. However, they tended to become higher as the molecular weight of PEG increased. The dissolution rate of the PAA/PEG polymer complex was much slower than the PAA/PEG blend, and was dependent on pH and molecular weight of the PEG. The mucoadhesive force of the PAA/PEG polymer complexes was stronger than for the PAA/PEG blend or a commercial product, Carbopol 971P NF. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2749–2754, 1999     

A mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poly(vinyl alcohol) for mucosal drug delivery

The interpolymer complexes composed of PVA and PAA were prepared by template polymerization of acrylic acid in the presence of PVA with different molecular weights and degrees of saponification. The carbonyl absorption band of the PAA in the PAA/PVA interpolymer complexes was shifted to a lower wavenumber due to H‐bonding between the carboxyl group of PAA and the hydroxyl group of PVA. The swelling ratio and the degree of dissolution of the PVA/PAA interpolymer complexes were dependent on the pH of the medium, the molecular weight, and the degree of saponification of the PVA. The release rate of a model drug, lidocaine, from the complexes decreased with increasing degree of saponification of the PVA due to the lower swelling degree of the complex. The adhesive force of the PVA/PAA interpolymer complexes with a plastic plate (poly propylene) was stronger than that of the commercial Carbopol 971P. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 327–331, 2004     

Effects of composition on the properties of dual physically cross-linked hydrogel composed of polyvinyl alcohol and poly (acrylamide-co-acrylic acid)

In previous work, we have developed a dual physically cross-linked hydrogel composed of poly (acrylamide-co-acrylic acid) (PAM-co-PAA) and polyvinyl alcohol (PVA), named as PVA/CP DN gel, by facile copolymerization and freezing/thawing. The PVA/CP DN gel is featuring both excellent mechanical properties and self-healing ability. Additionally, we have preliminarily found that the comonomer ratio for PVA/CP DN gel have great influence on the self-healing efficiency. In this research article, we will further discuss the mechanical and self-healing properties of the PVA/CP DN gel by varying the comonomer ratio of PAM-co-PAA. The results proved that the structure of DN will be loosen when the number of PAA segments exceed that of PAM. More PAA segments in copolymer make the PVA/CP DN gel have better elongation at break but weak in tensile strength and young’s modulus because of less PVA crystalline domains formed in the gel. The energy dissipation value for the double-network hydrogel decrease with the addition of PAA segments, whereas self-healing efficiency of PVA/CP DN gel increased. Anyway, this work provides more information to further understand the effects of composition on the properties of dual physically cross-linked PVA/CP DN hydrogel.     

Preparation method and physical,mechanical, thermal characterization of poly(vinyl alcohol)/poly(acrylic acid) blends

A series of blends of poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) were prepared by solution mixing and casting. Glycerol was used as plasticizer. The blends were characterized for their physicochemical and thermo-mechanical properties. The FTIR results revealed the molecular level interaction between PVA and PAA at all blend ratios. The incorporation of PAA significantly reduced the storage modulus of PVA at a given temperature. PVA gradually lost its crystalline character with the increase of PAA and became fully amorphous when the PAA content in the blend exceeded 50 wt%. The kinetic parameters of the semi-crystalline blends were determined using the Avarami–Erofeev model, which showed excellent fitting with the experimental data from DSC. The loss in crystallinity of PVA also contributed to an increase in swelling of the blend when the PAA content is increased. The morphology study by FE-SEM demonstrated that there is no phase separation among the blend components at all blend ratios.     

A mucoadhesive polymer prepared by template polymerization of acrylic acid in the presence of poly(ethylene glycol) macromer

A new mucoadhesive polymer complex was prepared by the template polymerization of acrylic acid with poly(ethylene glycol) macromer (PEGM) as a template polymer. Fourier transform infrared results showed that the poly(acrylic acid) (PAA)/PEGM mucoadhesive polymer complex was formed by hydrogen bonding between the carboxyl groups of PAA and the ether groups of PEGM. The glass‐transition temperature of the PAA/PEGM mucoadhesive polymer complexes was shifted to a lower temperature as the repeating unit ratio of PAA/PEGM in the complex decreased. The dissolution rate of the PAA/PEGM mucoadhesive polymer complex was much slower than that of the PAA/poly(ethylene glycol) (PEG) mucoadhesive polymer complex and was dependent on the pH and molecular weight of PEGM. The mucoadhesive force of the PAA/PEGM mucoadhesive polymer complexes was stronger than that of commercial Carbopol 971P NF and almost the same as that of the PAA/PEG mucoadhesive polymer complex. The PAA/PEGM interpolymer complex seemed to be a better mucoadhesive polymer matrix than the PAA/PEG interpolymer complex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1904–1910, 2002     

Release of diclofenac through gluteraldehyde crosslinked poly(vinyl alcohol)/poly(acrylic acid) alloy membranes

A controlled‐release preparation of diclofenac sodium for transdermal administration has been developed. Poly(vinyl alcohol) (PVA) and PVA/poly(acrylic acid) (PAA) alloy membranes were prepared from a solvent‐casting technique using different PVA/PAA (v/v) ratios. The release of the drug from the membrane was evaluated under in vitro conditions at pH 7.4. The delivery system provided linear release without time lag, burst effect, and boundary layer resistance. Effects of variables such as film thickness and PVA/PAA ratio on the permeation behavior of the polymeric membranes were discussed. The optimal PVA/PAA was determined as 50/50. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 72–77, 2004     

Synthesis and pH‐induced phase transition behavior of PAA/PVA nanogels in aqueous media

Polyacrylic acid (PAA) and polyvinyl alcohol (PVA) are well‐known FDA‐approved biocompatible polymers. A novel method for preparing PAA/PVA complex nanoneedles in PVA aqueous solution is presented in this article. The PAA/PVA complex nanogels are obtained via polymerization of acrylic acid monomer after PVA nanoparticles formed in water/acetone cosolvent. The results of TEM images showed that the PVA chains were aggregated to form gel particles with some erose nanoparticles. As AA monomers polymerized around PVA nanoparticles, PAA/PVA complex nanogels formed. The PAA/PVA nanogels had an average diameter of 300–100 nm with AA concentration of 0.5–2 g/100 mL. As acetone concentration varied, TEM images demonstrated that the morphologies of resulting nanogels are different. Without acetone in PVA aqueous solution, however, PAA/PVA complexes aggregated to form earthnut‐like particles. These results show that the shape and size of PVA/PAA nanogels can be tailored as a template or core for the formation of PAA/PVA nanogels. These PAA/PVA nanogels exhibited pH‐induced phase transition due to protonation of PAA chains. The novel PVA/PAA nanogels promise to be developed into pH‐controlled drug delivery system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Silicone secondary cross-linked IPN based on poly(vinylacetate-co-hydroxyethyl methacrylate) and SiO2

Silicone secondary cross-linked interpenetrating polymer networks (IPNs) of poly(vinylacetate-co-hydroxyethyl methacrylate) (PVAc-HEMA) and SiO₂ were prepared by free radical polymerization and condensation methods. The resulting copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR). Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology of copolymers was also investigated by optical microscopy (OM) and then the effects of silicone concentrations, the reflux time, and composition on the phase morphology of the IPNs of PVAc-HEMA/SiO₂ were discussed. The broadening of the transition region was observed with the increase of the prolongation of the reflux time and the tendency of the aggregation of silicon in the surface was also observed with Teflon as a substrate plate. However, an optically transparent film was easily achieved at higher temperature due to the chemical cross-link and physical entanglement between the two phases of PVAc-HEMA and SiO₂.     

Synthesis of poly(acrylic acid)–Fe3+/gelatin/poly(vinyl alcohol) triple‐network supramolecular hydrogels with high toughness,high strength and self‐healing properties

Hydrogels with good mechanical and self‐healing properties are of great importance for various applications. Poly(acrylic acid)–Fe³⁺/gelatin/poly(vinyl alcohol) (PAA‐Fe³⁺/Gelatin/PVA) triple‐network supramolecular hydrogels were synthesized by a simple one‐pot method of copolymerization, cooling and freezing/thawing. The PAA‐Fe³⁺/Gelatin/PVA triple‐network hydrogels exhibit superior toughness, strength and recovery capacity compared to single‐ and double‐network hydrogels. The mechanical properties of the synthesized hydrogels could be tailored by adjusting the compositions. The PAA‐Fe³⁺/Gelatin/PVA triple‐network hydrogel with 0.20 mmol Fe³⁺, 3% gelatin and 15% PVA could achieve good mechanical properties, the tensile strength and elongation at break being 239.6 kPa and 12.8 mm mm^?1, respectively, and the compression strength reaching 16.7 MPa under a deformation of about 91.5%. The synthesized PAA‐Fe³⁺/Gelatin/PVA triple‐network hydrogels have good self‐healing properties owing to metal coordination between Fe³⁺ and carboxylic groups, hydrogen bonding between the gelatin chains and hydrogen bonding between the PVA chains. Healed PAA‐Fe³⁺(0.20)/Gelatin3%/PVA15% triple‐network hydrogels sustain a tensile strength of up to 231.4 kPa, which is around 96.6% of the tensile strength of the original samples. Therefore, the synthesized triple‐network supramolecular hydrogels would provide a new strategy for gel research and expand the potential for their application. © 2019 Society of Chemical Industry