Ammonium Propane Sulfonate Research Articles

Investigation of charge effects on drug release behavior for ionic thermosensitive hydrogels

The influence of various drugs with different charges on the drug release behavior in porous ionic thermosensitive hydrogels was investigated. The present hydrogels were prepared from N-isopropylacrylamide (NIPAAm) and cationic monomer, trimethyl (acrylamido propyl) ammonium iodide (TMAAI), or anionic monomer, acrylic acid (AA), or zwitterionic monomer, N′, N′-dimethyl (acrylamido propyl) ammonium propane sulfonate (DMAAPS), or nonionic monomer, poly(ethylene glycol) methylether acrylate (PEGMEA), and pore-forming agent, poly(ethylene glycol) (PEG) with different molecular weights. Caffeine as a nonionic drug, crystal violet (CV) as a cationic drug solute, and phenol red as an anionic drug solute were chosen as model drugs to perform the drug release experiment. Results show that the release ratio of caffeine in the hydrogels is not affected by the ionicity of hydrogels. The CV strongly interacted with the anionic hydrogel; thus, the CV release ratio is very low. CV is only adsorbed on the skin layer of the cationic hydrogel due to charge repulsion and is released rapidly. The result of phenol red (anionic solute) release in the hydrogels is contrary to CV. In addition, the partition coefficients ( K d) and the drug delivery behavior of the present gels were also investigated.

Effect of salt and surfactant on aqueous solution properties of pyrene-labeled poly(3-dimethyl(methylmethacryloyl ethyl) ammonium propane sulfonate)

Photophysical and solution properties of pyrene-labeled poly(3-dimethyl(methylmethacryloyl ethyl) ammonium propane sulfonate), poly(DMAPS/Py), were studied in terms of fluorescence emission measurement. The IE/IM was shown as a function of polymer concentration in deionized water. IE/IM value decreases with an increase in the salt concentration. The addition of surfactants to the aqueous solution of poly(DMAPS/Py) can either induce the mixed micelle of intra-polymer and its surrounding surfactants and/or mixed micelle of inter-polymers and their surrounding surfactants. Models of interactions between poly(DMAPS/Py) and surfactant or divalent salt in aqueous solution are proposed.

Water‐soluble grafted polysaccharides containing sulfobetaine groups: Synthesis and characterization of graft copolymers of hydroxyethyl cellulose with 3‐dimethyl(methacryloyloxyethyl)ammonium propane sulfonate

AbstractNew water‐soluble grafted polysaccharides containing sulfobetaine groups were synthesized by the grafting of the sulfobetaine‐type zwitterionic monomer 3‐dimethyl‐(methacryloyloxyethyl)ammonium propane sulfonate (DMAPS) onto hydroxyethyl cellulose (HEC) in the presence of a ceric ammonium nitrate (CAN)/ethylenediaminetetraacetic acid (EDTA) initiation system. The effects of the concentrations of CAN, EDTA, DMAPS, and HEC, as well as the polymerization time and temperature, on the grafting reactions were investigated in terms of the grafting percentage (%GP) and grafting conversion (%GC) of the monomer. The %GP and %GC increased and then decreased with increasing concentrations of CAN, EDTA, and HEC. The %GP and %GC increased with increasing DMAPS concentration up to a certain value, beyond which the %GP did not significantly increase and the %GC decreased. The appropriate polymerization time and temperature were favorable for the grafting reactions. With infrared, thermogravimetric analysis, and viscosity measurements, the resulting grafted polysaccharides were characterized. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2755–2761, 2002; DOI 10.1002/app.10191

Thermoreversible Hydrogels XVI: Synthesis and Swelling Behaviors of [N-Isopropylacrylamide–co-trimethyl acrylamidopropyl ammonium iodide-co-3-dimethyl (methacryloxyethyl) ammonium propane sulfonate] Copolymeric Hydrogels in Aqueous Salt Solution

A series of copolymeric hydrogels were prepared from various molar ratios of N-isopropylacrylamide (NIPAAm), trimethyl acrylamidopropyl ammonium iodide (TMAAI), and 3-dimethyl (methacryloxyethyl) ammonium propane sulfonate (DMAPS). The swelling behaviors of these copolymeric hydrogels were investigated in various saline solutions. The result showed that the phase transition temperatures of these gels changed insignificantly, and the thermosensitivity, in contrast, diminished. In the saline solution, results showed that the swelling ratio of pure NIPAAm gel did not significantly change with an increase in the salt concentration until the salt concentration was larger than 0.5 M. In addition, the copolymer gels exhibited polyelectrolytic behavior under lower salt concentration (10−5–10−1 M), exhibited a nonionic gel (like NIPAAm) behavior at the salt concentration from 0.1 to 0.5 M, and showed an antipolyelectrolytic behavior (polyzwitterionic effect) at a concentration of salt over 0.5 M.

Grafting sulfobetaine monomer onto the segmented poly(ether-urethane) surface to improve hemocompatibility

Polyurethanes are widely used as blood-contacting biomaterials, due to their good biocompatibility and mechanical properties. Nevertheless, their blood compatibility is still not adequate for more demanding applications. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of the present study was to synthesize a novel nonthrombogenic biomaterial by modifying the surface of polyurethane. Ozonization was used to introduce active peroxide groups onto the segmented poly(ether-urethane) (SPEU) film surface and graft polymerization of N,N′-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate (DMAPS), a sulfobetaine structure, onto the ozone-activated SPEU surface was conducted. The SPEU-g-PDMAPS film was characterized by ATR-FTIR, XPS, and contact angle measurements. ATR-FTIR and XPS confirmed the graft polymerization. The grafted film possessed a relatively hydrophilic surface, as revealed by contact angle measurement. The blood compatibility of the grafted films was evaluated by a platelet-rich plasma (PRP) adhesion study and scanning electron microscopy, using SPEU film as the reference. No platelet adhesion was observed for the grafted films incubated with PRP at 37°C for 60 and 180 min. This new sulfobetaine structure grafted biomaterial might have potential for biomedical applications.

Thermoreversible hydrogels XIII: Synthesis and swelling behaviors of [N-isopropylacrylamide-co-sodium 2-acrylamido-2-methylpropyl sulfonate-co-N,N-dimethyl(acrylamido propyl) ammonium propane sulfonate] copolymeric hydrogels

A series of copolymeric hydrogels were prepared from various molar ratios of N-isopropylacrylamide (NIPAAm), sodium-2-acrylamido-2-methylpropyl sulfonate (NaAMPS) and N,N′-dimethyl(acrylamido propyl) ammonium propane sulfonate (DMAAPS). The swelling behaviors of these copolymeric hydrogels were investigated in various saline solutions. The result showed that the phase transition temperatures of these gels changed insignificantly, and the thermosensitivity, in contrast, diminished. In addition, the copolymer gels exhibited polyelectrolytic behavior under lower salt concentration (10−5∼10−1 M), exhibited a nonionic gel (like NIPAAm) behavior at the salt concentration from 0.1 to 0.4 M, and showed an antipolyelectrolytic behavior (polyzwitterionic effect) at a salt concentration over 0.4 M. Finally, the presented coplymeric gels are investigated for use in drug release application.

Chemical modification of polyaniline powders by surface graft copolymerization

Chemical modification of emeraldine (EM) based powders via thermally induced surface graft copolymerization with acrylic acid (AAc), 4-styrenesulfonic acid (SSAc) and amphoteric N,N′-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS) was carried out in aqueous media. The effects of temperature on graft copolymerization and Mohr's salt on homopolymerization were also studied. The chemical composition and structure of the graft-copolymerized powders were studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. In all cases, the graft yield increased with the monomer concentration and the temperature used for graft copolymerization. Certain Mohr's salts effectively inhibited the production of the homopolymers. Graft copolymerization with AAc and SSAc readily gave rise to self-protonated and semi-conductive EM powders, with the conductivity increasing with the extent of grafting. However, steric hindrance and spatial configuration of the grafted chains had substantially limited the extent of protonation of the EM substrate by the protonic acid functional groups of these chains.

Effects of polyelectrolyte complexation on the UCST of zwitterionic polymer

A zwitterionic polymer—poly-3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate (PDMAPS)—was synthesized and its complexation behaviors with polyanion: poly-2-acrylamido-2-methyl propane sulfonic acid (PAMPS); and polycation: poly-3-acryloylamino propyl trimethyl ammonium chloride (PDMAPAA-Q); or: x,y-ionene bromides (x=3,6; y=3,4) have been studied. One of the characteristic features of these complexes is that they are soluble, in spite of the abolishment of positive or negative charge of PDMAPS after the complexation and is able to exhibit UCST depending on the concentration and the mixing molar ratio. It was found that PDMAPS–PAMPS complex dramatically increases the viscosity to give a network structure through electrostatic interaction extensively decreasing the UCST, while the PDMAPS–polycation complex first decreases, but then increases the UCST without forming the network. The mechanism of different behaviors of these complexes has been discussed.

Thermoreversible hydrogels. VIII. Effect of a zwitterionic monomer on swelling behaviors of thermosensitive hydrogels copolymerized byN-isopropylacrylamide withN,N?-dimethyl (acrylamidopropyl) ammonium propane sulfonate

A series of thermosensitive hydrogels were prepared from the various molar ratios of N-isopropylacrylamide, zwitterionic monomer, N,N′-dimethyl (acrylamidopropyl) ammonium propane sulfonate (DMAAPS), and N,N′-methylene-bis-acrylamide. The influence of the amount of DMAAPS in the copolymeric gels on the swelling behaviors in water, various saline solutions, and various temperatures was investigated. Results indicated that the higher the DMAAPS content in the hydrogel system, the higher the swelling ratio and the gel transition temperature. In the saline solution results showed that, when the salt concentration was greater than the minimum salt concentration (MSC) of poly(DMAAPS), the deswelling behavior of the N-isopropylacrylamide gel was suppressed more effectively when more DMAAPS was added into the copolymeric gels; but the swelling ratios of the present copolymeric gels did not significantly change while the salt concentration was lower than the MSC of poly(DMAAPS). In addition, only the sample containing 12 mol % DMAAPS (D4) exhibited an antipolyelectrolyte's swelling behavior when the salt concentration was greater than the MSC of poly(DMAAPS). In other words, only when the amount of DMAAPS added into the gel is over some proportion, can the hydrogel show an antipolyelectrolyte's swelling behavior in concentrated salt solution. In saline solutions, the anion effects were greater than the cation effects in the presence of common anion (Cl−) with different cations and common cation (K+) with different cations for these gels. Finally, the more DMAAPS content in the hydrogel, the higher the diffusion coefficient in dynamic swelling. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2170–2180, 1999

Thermally induced surface graft copolymerization with concurrent lamination of polyaniline films under atmospheric conditions

Simultaneous lamination of emeraldine base (EB) films of polyaniline (PANI) was achieved during thermally induced surface graft copolymerization with various monomers, such as N,N′-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS), sodium salt of styrenesulfonic acid (NaSS), 1-vinyl imidazole (VIDz) and acrylic acid (AAc). The simultaneous thermal grafting and lamination process can be carried out under atmospheric conditions, and in the complete absence of an added polymerization initiator and surface preactivation of the EB substrates. The structure and chemical composition of the graft copolymerized surfaces from the self-delaminated junction in water were investigated by X-ray photoelectron spectroscopy (XPS). The effects of monomer concentration, thermal grafting/lamination temperature, and the physicochemical attributes of the various monomers on the observed lamination strength were studied. The efficiency of surface graft copolymerization and the lamination strength were found to increase with increasing temperature in the temperature range of 80–120°C. Maximum lap shear adhesion strengths of greater than 350 N/cm 2 and exceeding the yield strength of the substrate EB film could be readily achieved for grafting/lamination carried out in the presence of DMAPS, VIDz and AAc monomer.

Superabsorbent polymeric materials. VI. Effect of sulfobetaine structure on swelling behavior of crosslinked poly(sodium acrylate-co-sulfobetaines) in aqueous salt solutions

A series of xerogels based on sodium acrylate (SA), N,N-dimethyl(acrylamidopropyl) ammonium propane sulfonate (DMAAPS) or dimethyl(methacryloyloxy ethyl) ammonium propane sulfonate (DMAPS), and N,N′-methylene bisacrylamide (NMBA) was prepared by inverse suspension polymerization. The water absorbencies or swelling kinetic behaviors for these xerogels in water or various saline solutions were investigated. The swelling behaviors of these absorbents were related to their chemical structures, their compositions, and the nature of external salt solutions. The water absorbencies of these two copolymeric gel series in deionized water or in various salt solutions would be improved effectively by copolymerizing SA with a small amount of zwitterionic monomer (DMAAPS or DMAPS). The water absorbency of the gel containing DMAPS is larger than that of the gel containing DMAAPS when the amount of zwitterionic monomer in the copolymeric gel is 0.8 mol %. The tendency of the absorbency for these gels in dilute solution is in the order Cu2+ > Zn2+ > Co2+ > Ni2+ for CuCl2, ZnCl2, CoCl2, and NiCl2 aqueous solution, respectively. The absorbency and initial absorption rate for those gels are related with gel compositions and salt concentrations. Finally, the adsorption of cupric ion by these gels is also investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1221–1232, 1999

Surface modification of polymers for adhesion enhancement

Surface modification of low-density polyethylene (LDPE) and polytetrafluoroethylene (PTFE) films via graft copolymerization with acrylic acid (AAc), Na salt of styrenesulfonic acid (NaSS), N,N-dimethylacrylamide (DMAA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), glycidyl methacrylate (GMA), acrylamide (AAm) and 3-dimethyl(methacryloylethyl) ammonium propanesulfonate (DMAPS) was carried out for adhesion improvements. The surface microstructure and composition of the modified film surfaces were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). It was demonstrated that the graft-modified LDPE and PTFE films are capable of exhibiting adhesive-free adhesion or auto-adhesion. The GMA graft copolymerized PTFE surfaces adhere strongly to one another when brought into direct contact and cured (i) in the presence of an epoxy adhesive and (ii) in the presence of a diamine curing agent alone. It was further demonstrated that the ozone-pretreated LDPE films and the Ar plasma pretreated PTFE films readily undergo photografting or thermal grafting with concurrent lamination when lapped together in the presence of a small quantity of the monomer solution. The simultaneous graft copolymerization and lamination process can be carried out under atmospheric conditions and in the complete absence of an added initiator or system degassing. Copyright © 1999 John Wiley & Sons, Ltd.

Poly(2-hydroxyethyl methacrylate-co-sulfobetaine)s hydrogels: 3. Synthesis and swelling behaviors of the [2-hydroxyethyl methacrylate-co-N,N′-dimethyl (acrylamido propyl) ammonium propane sulfonate] hydrogels

A series of the 2-hydroxyethyl methacrylate/N,N′-dimethyl-(acrylamido propyl) ammonium propane sulfonate (HEMA/DMAAPS) copolymeric gels has been prepared from various molar ratios of HEMA and the zwitterionic monomer DMAAPS. The influence of the amount of zwitterionic monomer in the copolymeric gels on the swelling behaviors in water, various saline solutions, and various temperatures was investigated. Results indicated that in the equilibrium swelling ratio (Qeq), the PHEMA hydrogel exhibited a minimum Qeq at 55°C. Then, the minimum Qeq was more obvious when higher zwitterionic monomer, DMAAPS, content was added into the HEMA/DMAAPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/DMAAPS copolymer gels increased rapidly with increasing concentration of the salt, and with smaller ratio of charge/radius. In dynamic swelling behaviors, the PHEMA hydrogel (DM0) and the HEMA/DMAAPS copolymeric gels with lower DMAAPS content (DM1 and DM2) exhibited overshoot phenomena. The maximum overshoot value decreases with increase in temperature.

Surface graft copolymerization of low density polyethylene films and its relevance to auto-adhesion

The surfaces of low density polyethylene (LDPE) films were modified first by ozone pretreatment, followed by thermally-induced graft copolymerization with the amphoteric monomer, 3-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS). The DMAPS graft copolymerized LDPE films were capable of exhibiting adhesive-free adhesion when brought into contact in the presence of water and subsequently dried. Lap shear adhesion strengths in excess of 100 N/cm 2 were achieved for lamination carried out at elevated temperature (60°C). It was also demonstrated that when two ozone-pretreated LDPE films were brought into contact in the presence of a small quantity of the aqueous DMAPS solution at an elevated temperature (70°C and above), surface graft copolymerization with concurrent lamination were achieved under atmospheric conditions and in the complete absence of an added polymerization initiator or oxygen scavenger. The adhesion strengths in both cases were governed by the concentration-dependent chain diffusion and entanglement, as well as by the electrostatic interaction, at the lapped interface. The graft copolymerized surfaces in both cases were characterized by X-ray photoelectron spectroscopy (XPS).

Poly(2-hydroxyethyl methacrylate-co-sulfobetaine) hydrogels. II. Synthesis and swelling behaviors of the [2-hydroxyethyl methacrylate-co-3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate] hydrogels

A series of the 2-hydroxyethyl methacrylate/3-dimethyl-(methacryloyloxy-ethyl)ammonium propane sulfonate (HEMA/DMAPS) copolymeric gels was prepared from various molar ratios of HEMA and the zwitterionic monomer DMAPS. The influence of the amount of the zwitterionic monomer in the copolymeric gels on the swelling behaviors in water, various saline solutions, and temperature was investigated. The results indicate that the PHEMA hydrogel (DO) and lower DMAPS content of the HEMA/DMAPS copolymeric gel (D1) exhibit overshooting phenomena in the dynamic swelling behavior. The maximum overshooting value decreases with increase in temperature. In the equilibrium swelling ratio, the PHEMA hydrogel exhibits a minimum swelling ratio at 55°C, Then, the minimum swelling ratio diminishes gradually with increasing of the DMAPS content in the HEMA/DMAPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/DMAPS copolymeric gels increase rapidly with increasing of concentration of the salt with a smaller ratio of the charge/radius.

Surface Modification of Low-Density Polyethylene Films by UV-Induced Graft Copolymerization and Its Relevance to Photolamination

Surface modification of ozone-pretreated low-density polyethylene (LDPE) films were carried out via a novel technique of UV-induced graft copolymerization with acrylamide (AAm), Na salt of styrenesulfonic acid (NaSS), 3-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS), acrylic acid (AAc), N,N-dimethylacrylamide (DMAA), and 2-(dimethylamino)ethyl methacrylate (DMAEMA) under atmospheric conditions and in the complete absence of an added initiator or oxygen scavenger. Photografting with concurrent photolamination in assemblies containing a monomer solution sandwiched between two LDPE films was demonstrated. The chemical composition and microstructure of the graft copolymerized surfaces were studied by angle-resolved X-ray photoelectron spectroscopy. For LDPE films with high graft concentrations, such as those graft copolymerized with AAm, DMAA, and DMAEMA, surface chain rearrangement to form a stratified surface microstructure with a higher substrate to graft chain ratio at the outermost surface ...

Surface modification and adhesion characteristics of polycarbonate films after graft copolymerization

The surfaces of ozone-pretreated polycarbonate films were subjected to further modification by thermally induced graft copolymerization with acrylic acid (AAc), sodium salt of styrene sulfonic acid (NaSS), N,N-dimethylacrylamide (DMAA), N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and 3-dimethyl(methacryloyl ethyl)-ammonium propanesulfonate (DMAPS) monomers. The structure and composition at the copolymer interface were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). For polycarbonate films with a substantial amount of grafted polymer, the hydrophilic graft penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains. This microstructure was further supported by the water contact angle measurements. Adhesive-free adhesion studies revealed that the AAc, DMAA or DMAPS graft copolymerized polycarbonate film surface adhered strongly to another similarly modified surface (homo-interface) when brought into direct contact in the presence of water and subsequently dried. The development of the lap shear strength is dependent on the concentration of the surface graft, the microstructure of the grafted surface, the adhesion (drying) time, and the nature of the interfacial interaction. The simultaneous presence of chain entanglement and electrostatic interaction readily results in substantially enhanced adhesion strengths between two DMAPS graft copolymerized surfaces or between an AAc and a DMAA graft copolymerized surface (hetero-interface). XPS analyses of the delaminated surfaces suggest that failure occurred cohesively below the graft-substrate interface. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 357–366, 1998

Surface modification of polymer films by graft copolymerization for adhesive-free adhesion

The surfaces of low density polyethylene (LDPE), poly(carbonate) (PC), polytetrafluoroethylene (PTFE) and emeraldine (EM) base films of poly(aniline) are modified by graft copolymerization with N,N-dimethylacrylamide (DMAA), Na salt of styrenesulfonic acid (NaSS), 3-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS) and acrylic acid (AAc). Two surface graft copolymerized films are capable of exhibiting ‘adhesive-free’ adhesion or auto-adhesion when brought into contact in the presence of water and subsequently dried. The development of the lap shear adhesion strength depends upon the concentration of the surface graft, the contact adhesion (drying) time, the nature of the substrate, the microstructure of the graft copolymerized surfaces and the extent of molecular interaction (dispersive, electrostatic, etc.) at the lapped junction. Lap shear adhesion strengths in excess of 90 N cm −2 were readily achieved between films graft copolymerized with the amphoteric DMAPS, as well as between a DMAPS graft copolymerized EM film and an AAc graft copolymerized PTFE film. X-ray photoelectron spectroscopy (x.p.s.) analysis of the delaminated surfaces suggests that the failure mode involves the fracture of the graft chains at the substrate-graft interface.

Surface-Functionalized Polyaniline Films

The surfaces of emeraldine (EM) base films of polyaniline (PANi) have been functionalized by thermal graft copolymerization with acrylic acid (AAc) and N,N-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS). The AAc graft copolymerized EM films were further functionalized via covalent immobilization of glucose oxidase (GOD) and collagen. The so-immobilized GOD still retains a substantial amount of activity. The amphoteric DMAPS graft copolymerized EM base films are capable of exhibiting strong adhesive-free adhesion to one another and to another similarly modified dielectric film, such as a surface graft copolymerized poly(tetrafluoroethylene) (PTFE) film. Lap shear adhesion strengths on the order of 300 and 100 N/cm2 were obtained for the respective cases. Pristine PANi films of various intrinsic oxidation states are capable of undergoing spontaneous surface metallization through reduction of precious metal ions, such as gold and palladium, in acid solutions to their elemental forms. The rate o...

Superabsorbent polymeric materials. IV. Swelling behavior of crosslinked poly [sodium acrylate-co-N,N-dimethyl (acrylamidopropyl) ammonium propane sulfonate] in aqueous salt solution

A series of xerogels based on sodium acrylate (SA), N,N-dimethyl(acrylamidopropyl)ammonium propane sulfonate (DMAAPS), and N,N′-methylene bisacrylamide (NMBA) were prepared by inverse suspension polymerization. The water absorbency or swelling behavior for these xerogels in water or various saline solutions was investigated. Results obtained from this study revealed a water absorbency of 721 g H2O/g sample in deionized water and 83 g H2O/g sample in 0.9 wt % NaCl solution for a gel containing a 1.50 × 10 −2 molar fraction of DMAAPS. The absorbency in the chloride salt solutions decreased with an increase in the ionic strength of the salt. For the same ionic strength of various salt solutions, the swelling amount had the following tendency: Co 2+ > Ni 2+ > Cu 2+ for the higher ionic strength of 2.44 × 10 −5–1.8 × 10 −2M. The Co 2+, Ni2+, and Cu 2+ solutions induce approximately the same degree of swelling at the lower ionic strength of <2.44 × 10 minus;5M. The pH effect on the water absorbency for these xerogels was also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66:499–507, 1997