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.     

Properties of interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) and poly(N‐isopropylacrylamide) were prepared by the sequential‐IPN method. The IPN hydrogels were analyzed for sorption behavior of water at 35°C and at a relative humidity of 95% using a dynamic vapor sorption system, and water diffusion coefficients were calculated. Differential scanning calorimetry was used for the quantitative determination of the amounts of freezing and nonfreezing water. Free water contents in the IPN hydrogel of IPN1, IPN2, and IPN3 were 45.8, 37.9 and 33.1% in pure water, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2041–2045, 2003     

Electroactive characteristics of interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

An interpenetrating polymer network (IPN) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) was prepared by the sequential IPN method. The equilibrium swelling ratio and bending behavior under electric fields of the IPN hydrogel were measured in an aqueous NaCl solution. The IPN exhibited a high equilibrium swelling ratio, in the range 280–380%. When the IPN in aqueous NaCl solution was subjected to an electric field, the IPN showed significant and quick bending toward the cathode. The IPN hydrogel also showed stepwise bending behavior, depending on the electric stimulus. In addition, the ionic conductivity of the IPN hydrogel was measured using dielectric analysis, and its conductive behavior followed the Arrhenius equation. The conductivity of the IPN hydrogel and the activation energy for the form of the IPN were 1.68 × 10^?5 S/cm at 36°C and 61.0 kJ/mol, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 890–894, 2003     

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.     

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     

Synthesis and characterization of an interpenetrating polymer network composed of poly(methacrylic acid) and poly(vinyl alcohol)

Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry     

Sorption characterization of poly(vinyl alcohol)/chitosan interpenetrating polymer network hydrogels

Poly(vinyl alcohol) (PVA)/chitosan interpenetrating polymer networks (IPN) were prepared by UV irradiation. The water sorption behavior of the IPNs was measured at various temperatures and humidity levels. The water uptake of IPN13 is greater than that of other IPNs. Vapor sorption behavior is more affected by the density of water vapor than by hydrophilic properties with increasing temperature. Equilibrium water uptake increases as humidity increases, and the increase is more noticeable at high humidity. The sorption system of all IPNs is a relaxation‐controlled mechanism at a relative humidity (RH) of 90%, but it is a Fickian diffusion‐controlled mechanism when the RH is below 50%. With an increase in humidity, the diffusion coefficients were found to increase due to greater penetration of water into the IPNs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 86–90, 2003     

Water sorption of poly(vinyl alcohol)/ poly(diallyldimethylammonium chloride) interpenetrating polymer network hydrogels

Temperature‐responsive interpenetrating polymer network (IPN) hydrogels constructed with poly(vinyl alcohol) and poly(diallyldimethylammonium chloride) using the sequential IPN method were studied. The characteristics of IPN hydrogels were investigated using the dynamic vapor sorption system. IPN hydrogels exhibited a relatively high sorption ratio, 180–360% at room temperature. The sorption ratio of hydrogels depended on temperature. Diffusion coefficients were calculated according to the Fickian Law at several temperatures. The apparent activation energy was 5.43 kJ mol^?1, which corresponds to typical diffusion processes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1389–1392, 2003     

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.     

Synthesis and characteristics of interpenetrating polymer network hydrogel composed of chitosan and poly(acrylic acid)

Interpenetrating polymer network (IPN) hydrogels composed of chitosan and poly(acrylic acid) (PAAc) were synthesized by UV irradiation method, and their structure, crystallinity, swelling behavior, thermal property, and mechanical property were investigated. Chitosan/PAAc IPNs exhibited relatively high equilibrium water content and also showed reasonable sensitivity to pH. From the swelling behaviors at various pH's, Fourier transform infrared spectra at high temperature and thermal analysis confirmed the formation of polyelectrolyte complex due to the reaction between amino groups in chitosan and carboxyl groups in PAAc. For this reason, even at a swollen state, the present chitosan/PAAc IPNs possess good mechanical properties. Particularly, the CA‐2 sample (with a weight ratio of chitosan/PAAc = 50/50, molar ratio [NH₂]/[COOH] = 25/75) showed the lowest equilibrium water content and free water content, attributed to the more compact structure of the polyelectrolyte than CA‐1 or CA‐3 due to the high amount of interchain bond within the IPN. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 113–120, 1999     

Electrochemical behavior of an interpenetrating polymer network hydrogel composed of poly(propylene glycol) and poly(acrylic acid)

An interpenetrating polymer network (IPN) hydrogel based on poly(propylene glycol) and poly(acrylic acid) was prepared by UV irradiation. The swelling behavior of the IPN hydrogel was studied by the immersion of the gel in aqueous NaCl solutions of various concentrations. The swelling ratio decreased with an increase in the NaCl concentration. The electrically sensitive behavior of the IPN hydrogel in electric fields was also investigated. The IPN hydrogel also showed a stepwise bending behavior that depended on the electric stimulus. The bending angle and bending speed of the IPN hydrogel were greatest in 0.6 wt % aqueous NaCl and increased with an increase in the applied voltage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2301–2305, 2003     

Microwave-induced shape-memory poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks chemically linked to SiC nanoparticles

Microwave (MW)-induced shape-memory poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) interpenetrating polymer networks (SMP-IPNs) were prepared through in situ polymerization. Silicon carbide (SiC) nanoparticles were modified by 3-(methacryloyloxy) propyltrimethoxysilane (KH570). 3-(Methacryloyloxy) propyltrimethoxysilane was covalently bonded on the surface of SiC through the reaction of silanol and the methoxy groups. The polymerization of acrylic acid (AA) using N,N′-methylenebis (2-propenamide) (MBA) as cross-linker in PVA solution was initiated through the double bonds of KH-570 grafted on SiC, leading to a PAA polymer network cross-linked with MBA. The PVA molecular chains run through the PAA cross-linking network and form an IPN structure. Therefore, SiC as a strong MW absorbing material could be chemically cross-linked into polymer matrix. The effect of composition on the properties of SMP-IPN was studied using dynamic mechanical analysis, dielectric properties and shape memory effect (SME) test. The results showed that the introduction of SiC in IPNs not only provided samples with excellent MW-induced shape memory effect (SME), but also caused a higher equilibrium temperature under MW irradiation. Moreover, both SiC content and applied MW power affected the shape recovery properties of PVA/PAA interpenetrating composites. MW-induced SMPs offered great advantages such as fast recovery, high recovery rate, and remote actuation. This study provides the potential applications of the fast and environmentally friendly SMPs used as MW-responsive sensors, implantable devices, etc.     

Swelling behavior of semi‐interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(acrylamide‐co‐sodium methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐sodium methacrylate) poly(AAm‐co‐SMA) were prepared by the semi IPN method. These IPN hydrogels were prepared by polymerizing aqueous solution of acrylamide and sodium methacrylate, using ammonium persulphate/N,N,N¹,N¹‐tetramethylethylenediamine (APS/TMEDA) initiating system and N,N¹‐methylene‐bisacrylamide (MBA) as a crosslinker in the presence of a host polymer, poly(vinyl alcohol). The influence of reaction conditions, such as the concentration of PVA, sodium methacrylate, crosslinker, initiator, and reaction temperature, on the swelling behavior of these IPNs was investigated in detail. The results showed that the IPN hydrogels exhibited different swelling behavior as the reaction conditions varied. To verify the structural difference in the IPN hydrogels, scanning electron microscopy (SEM) was used to identify the morphological changes in the IPN as the concentration of crosslinker varied. In addition to MBA, two other crosslinkers were also employed in the preparation of IPNs to illustrate the difference in their swelling phenomena. The swelling kinetics, equilibrium water content, and water transport mechanism of all the IPN hydrogels were investigated. IPN hydrogels being ionic in nature, the swelling behavior was significantly affected by environmental conditions, such as temperature, ionic strength, and pH of the swelling medium. Further, their swelling behavior was also examined in different physiological bio‐fluids. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 302–314, 2005     

Synthesis and characteristics of interpenetrating polymer network hydrogels composed of alginate and poly(diallydimethylammonium chloride)

Temperature‐ and pH‐responsive interpenetrating polymer network (IPN) hydrogels, with sodium alginate (SA) and poly(diallydimethylammonium chloride) (PDADMAC), constructed by a sequential IPN method, were studied. The characterizations of the IPN hydrogels were investigated by FTIR, DSC, and swelling tests under various conditions. The prepared IPN hydrogels exhibited relatively high swelling ratios, in the range of 380–690%, at 25°C. The swelling ratios of SA/PDADMAC IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the freezing and nonfreezing water contents of the hydrogels. The amount of free water increased with the increasing PDADMAC content of the IPN hydrogels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3705–3709, 2004     

Thermal characteristics of interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by the sequential‐IPN method. The thermal characterization of the IPNs was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depression of the melting temperature (T_m) of the PVA segment in IPNs was observed with increasing PNIPAAm content using DSC. DEA was employed to ascertain the glass‐transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_g values, indicating the presence of phase separation in the IPNs. The thermal decomposition of IPNs was investigated using TGA and appeared at near 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 881–885, 2003     

Poly(vinyl alcohol)/poly(vinyl pyrrolidone) interpenetrating polymer network: Synthesis and pervaporation properties

Novel interpenetrating polymer network membranes were made from poly(vinyl alcohol)/poly(vinyl pyrrolidone) blends of different compositions. The two polymer components were independently crosslinked chemically with glutaraldehyde and photochemically with 4,4′‐diazostilbene‐2,2′‐disulfonic acid disodium salt. The membrane performances were studied in pervaporation of tetrahydrofuran (THF)/water and THF/methanol mixtures. It was found that the membranes were excellent in THF dehydration, but much less efficient for the separation of THF/methanol mixtures. The pervaporation results were consistent with the membrane swelling data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2808–2814, 2003     

Preparation and characterization of pH-sensitive,interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid)

Hydrogels with varying cross-linking ratio and ionic content were prepared from interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid). Equilibrium swelling studies were conducted and the average molecular weight between cross-links, M _c, and mesh size were determined. Hydrogels with large M _c, values were found to swell to a greater extent than those with small M _c values. It was also observed that an increase in M _c yielded faster swelling and deswelling rates, as the rates for membranes with M _c = 18,000 were about twice as fast as were the rates for membranes with M _c = 34,000. Oscillatory swelling behavior was investigated in response to changes in the pH and ionic strength of the swelling medium. A change in pH from 3 to 6 caused an ionization of the hydrogels and an increase in the weight swelling ratio, with a greater increase exhibited by IPNs with a higher ionic content. Increase in pH also caused an increase in the average mesh size. © 1995 John Wiley & Sons, Inc.     

Pervaporation of nonaqueous ethanol azeotropes through interpenetrating polymer network membranes prepared from poly(4-vinylpyridine) and poly(vinyl alcohol)

Highly hydrophilic interpenetrating polymer network (IPN) membranes were prepared from a mixture system of poly(4-vinylpyridine) (P4VP) and poly(vinyl alcohol) (PVA) by quaternizing crosslinking of P4VP with 1,4-dibromobutane (DBB) and simultaneous crosslinking of PVA with hexamethylene diisocyanate (HMDI). The membrane performance in pervaporation (PV) for the azeotropic mixture of ethanol with a less polar organic liquid (chloroform, benzene, carbon tetrachloride, and cyclohexane) was investigated. The strength of these IPN membranes was higher than that of the cellulose acetate membrane and depended on the membrane composition. All the membranes were ethanol permselective for the azeotropic feeds and equimolar mixture feeds as well. Only the swelling degree Q of the membrane, among several physicochemical factors, showed a relationship with the separation performance for the four feeds; a lower value of Q generally corresponded to a higher separation factor and smaller permeability. The membrane composition, which exhibited an optimum membrane performance, was examined in detail for some membranes. Both the separation factor for sorption and that for diffusion far exceeded unity, but the latter was greater in most cases than was the former and dominated the overall separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2729–2738, 2001     

Permeation of solutes in water-swollen poly(vinyl alcohol-co-itaconic acid) membranes

Partition and permeability coefficients of urea, NaCl, and saccharose in water-swollen poly(vinyl alcohol-co-itaconic acid) membranes with various water contents (0.25 ? H ? 0.86) were measured. Partition coefficients and permeability ratios in freezing and nonfreezing water were estimated based on a parallel permeation model. It was suggested that at 25°C the permeation of saccharose in the nonfreezing water was nearly zero due to its negligible partition coefficient, while NaCl and urea were found to be able to permeate even the nonfreezing water. The activation energies of diffusion for three solutes were found to increase with the decrease of water content of the membranes. Since the fraction of nonfreezing water increased with the decrease of water content of the membranes, it is assumed that the increased activation energy of diffusion is due to the fact that the diffusion in nonfreezing water needs higher activation energy than in the pure bulk water.     

Properties of electroresponsive poly(vinyl alcohol)/poly(acrylic acid) IPN hydrogels under an electric stimulus

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) exhibited electrical-sensitive behavior. PAAc as an initial network was prepared inside a PVA solution using UV irradiation; then, PVA networks as a secondary network were formed by a repetitive freeze–thawing process. Their mechanical properties were influenced by the swelling ratio, crosslinking by UV radiation and a freeze–thawing process, and intermolecular force by hydrogen bonding. When a swollen PVA/PAAc IPN was placed between a pair of electrodes, the IPN exhibited bending behavior upon the applied electric field. The equilibrium bending angle (EBA) and the bending speed of the PVA/PAAc IPN increased with the applied voltage and the content of the PAAc network having negatively charged ionic groups within the IPN. The electroresponsive behavior of the present IPN was also affected by the electrolyte concentration of the external solution. Particularly, IPN37 showed a maximum EBA when the critical ionic strength was 0.1. Anisotropic deswelling of the IPN was observed in a direct contact with a pair of electrodes under aerobic conditions. The PVA/PAAc IPN also showed stepwise bending behavior depending on the electric stimulus. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1675–1683, 1999