Synthesis and swelling properties of 2‐hydroxyethyl methacrylate‐co‐1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine hydrogels

A series of 2‐hydroxyethyl methacrylate/1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine (HEMA/VSIB) copolymeric gels were prepared from various molar ratios of HEMA and the zwitterionic monomer VSIB. The influence of the amount of VSIB in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures and the drug‐release behavior, compression strength, and crosslinking density were investigated. Experimental results indicated that the PHEMA hydrogel and the lower VSIB content (3%) in the HEMA/VSIB gel exhibited an overshooting phenomenon in their dynamic swelling behavior, and the overshooting ratio decreased with increase of the temperature. In the equilibrium water content, the value increased with increase of the VSIB content in HEMA/VSIB hydrogels. In the saline solution, the water content for these gels was not affected by the ion concentration when the salt concentration was lower than the minimum salt concentration (MSC) of poly(VSIB). When the salt concentration was higher than the MSC of poly(VSIB), the deswelling behavior of the copolymeric gel was more effectively suppressed as more VSIB was added to the copolymeric gels. However, the swelling behavior of gels in KI, KBr, NaClO₄, and NaNO₃ solutions at a higher concentration would cause an antipolyelectrolyte phenomenon. Besides, the anion effects were larger than were the cation effects in the presence of a common anion (Cl^?) with different cations and a common cation (K⁺) with different anions for the hydrogel. In drug‐release behavior, the addition of VSIB increased the drug‐release ratio and the release rate. Finally, the addition of VSIB in the hydrogel improved the gel strength and crosslinking density of the gel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2888–2900, 2001     

Chitosan–polyelectrolyte complexation for the preparation of gel beads and controlled release of anticancer drug. II. Effect of pH‐dependent ionic crosslinking or interpolymer complex using tripolyphosphate or polyphosphate as reagent

Chitosangel beads were prepared using an in‐liquid curing method by ionotropic crosslinking or interpolymer linkage with tripolyphosphate (TPP) or polyphosphate (PP). The ionic interaction of chitosan with TPP or PP is pH‐dependent due to the transition of “ladder‐loop” complex structures. Chitosan gel beads cured in a pH value lower than 6 of a TPP solution was a controlled homogeneous ionic‐crosslinking reaction, whereas chitosan gel beads cured in a lower pH PP solution was a nonhomogeneous interpolymer complex reaction due to the mass‐transfer resistance for the diffusion of macromolecular PP. According to the results of FTIR and EDS studies, it was suggested that significantly increasing the ionic‐crosslinking density or interpolymer linkage of a chitosan–TPP or chitosan–PP complex could be achieved by transferring the pH value of curing agent, TPP or PP, from basic to acidic. The swelling behavior of various chitosan beads in acid medium appeared to depend on the ionic‐crosslinking density or interpolymer linkage of the chitosan–TPP or chitosan–PP complex, which were deeply affected by the in‐liquid curing mechanism of the chitosan gel beads. By the transition of the in‐liquid curing mechanism, the swelling degree of chitosan–TPP or chitosan–PP beads was depressed and the disintegration of chitosan–TPP or chitosan–PP beads did not occur in strong acid. The drug‐release patterns of the modified chitosan gel beads in simulated intestinal and gastric juices were sustained for 20 h. These results indicate that the sustained release of anticancer drugs could be achieved due to the variation of the reaction mechanism of a chitosan–polyelectrolyte pH‐dependent ionic interaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1093–1107, 1999     

Swelling characteristics of block order networks prepared by styrene-ethylene/butylene ABA triblock copolymer and styrene homopolymer binary blends

Mixed networks based on polystyrene (PS) and styrene-ethylene/butylene triblock copolymer (SEBS) binary blends were synthesized via a postpolymerization Friedel-Crafts-type reaction employing styrene units and a bis-chloromethylated crosslinking agent. The swelling behavior of the produced gels was studied in relation to network densty, SEBS/PS mass ratio, and solubility parameter of the swelling media, in a range of aliphatic, chlorinated, and aromatic solvents. Swelling characteristics of the mixed macronets were found to differ markedly from those of pure homopolymer gels. Selective swelling was observed in three different regions in respect to the solvent solubility parameter, in contrast to pure PS networks where adsorption was favored in a single region of solvents. This phenomenon was found to depend primarily on the SEBS/PS constitution of gels, while the solvent holding capacity depended directly on the crosslinking density. © 1995 John Wiley & Sons, Inc.     

Investigation of mechanical and thermodynamic properties of pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with different crosslinking agents

pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels were synthesized by free‐radical crosslinking polymerization using two different crosslinking agents; tetraethylene glycol dimethacrylate (TEGMA) and N,N′‐methylenebis(acrylamide) (BAAm). The influence of the polymerization factors such as the type of the crosslinking agent and the gel preparation concentration on the swelling behavior, the gel strength, the effective crosslinking density and the average chain length between the crosslink points for the resulting hydrogels was investigated. The results of the equilibrium swelling measurements in water showed that the linear swelling ratio of the resulting hydrogels increases with increasing gel preparation concentration. The swelling ratio of PDMAEMA hydrogels crosslinked with BAAm is larger than those for hydrogels crosslinked with TEGMA over the entire range of the polymer network concentration. The hydrogels exhibit very sharp pH‐sensitive phase transition in a very narrow range of pH between 7.7 and 8.0. From the mechanical measurements, it was also found that the linear swelling ratio of resulting hydrogels depends on the crosslinking density and also the type of the crosslinker used in the preparation. The resulting hydrogels are thought to be good candidates for pH‐sensitive drug delivery systems. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Syntheses of hydroxypropyl methylcellulose phthalate hydrogels in Na2CO3 aqueous solutions with electron‐beam irradiation

Novel cellulose ether hydrogels were prepared by the radiation‐induced crosslinking of hydroxypropyl methylcellulose phthalate (HPMCP) in a solution of Na₂CO₃. The effects of several factors, such as the HPMCP concentration, Na₂CO₃ concentration, absorbed dose, and dose rate, on the crosslinking of HPMCP were investigated in detail. An increase in the HPMCP concentration resulted in an increasing content of the gel fraction, and this meant that the crosslinking probability increased as well. Na₂CO₃ was essential for dissolving HPMCP in water, and a 4–5% Na₂CO₃ aqueous solution was optimal for the crosslinking of HPMCP. The dose rate also affected the radiation crosslinking of HPMCP; hydrogels with higher gel fractions and transparency could be formed at lower dose rates. The ratio of degradation to crosslinking of the gel was calculated according to the Charlesby–Rosiak equation, and it showed good agreement with the experimental results. Some important properties, such as the swelling kinetics, ion and ionic strength dependence, and pH dependence, of the HPMCP hydrogels were also investigated. The HPMCP hydrogels possessed excellent swelling rates and swelling ratios in some solvents, such as water and methanol, with a high hydrogen‐bonding parameter. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2123–2130, 2003     

Curing of polyfurfuryl alcohol resin catalyzed by a homologous series of dicarboxylic acid catalysts. II. Swelling behavior and thermal properties

Polyfurfuryl alcohol (PFA), as a bio‐based resin made from lignocellulosic materials, was crosslinked using a homologous series of dicarboxylic acid catalysts consisting of oxalic, succinic, and adipic acids, which are different in their dissociation constants. Swelling behavior, thermal stability, and non‐oxidative char residue of the resulting networks were characterized as a function of the acids strength and their concentration. Swelling of the networks were investigated at room temperature in eight solvents differing in molecular size and solubility parameter. Using acetonitrile as a solvent, the swelling mechanism was explored by applying kinetic models to the swelling data. Dynamic swelling studies during 16–30 days supported non‐Fickian and anomalous diffusion mechanism in highly crosslinked samples supporting PFA chain rigidity and high crosslinking density of the networks. Polymer–solvent interaction parameter, molecular weight between crosslinks and crosslinking densities were also determined. According to the results, the extent of PFA crosslinking and non‐Fickian behavior of the swelling solvent diffusion through the networks are strongly dependent on the concentration and dissociation characteristics of the catalysts used. Thermal stability studies showed no significant differences between the compositions, up to 900 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45770.     

Modified Poly(Vinyl Alcohol) and Coconut Shell Powder Composite Films: Physico-Mechanical,Thermal Properties,and Swelling Studies

Cross-linked poly(vinyl alcohol) (PVA) was blended with 10, 20, 33, and 50 wt. % of coconut shell (CCS) powder by a solution casting process. The solution-casted PVA/CCS powder films were dried and characterized for physico-mechanical properties, such as tensile, tear, and burst strengths, and density. The influence of CCS powder addition on moisture content, moisture vapor transmission rate (MVTR), solubility, swelling, and the thermal transition of PVA/CCS powder composite films have been studied. The PVA/CCS powder composite films show enhancement in elastic modulus, solubility resistance in water, 5% acetic acid, 50% ethanol, moisture vapor transmission rate, and moisture resistance. However, the introduction of CCS powder affects tensile strength, percentage of elongation, tear and burst strengths, moisture content, and swelling capacity Considerably.     

Synthesis and swelling characteristics of responsive carboxybetaine gel

A polyimminium gel, Dimedone‐[N, N′ melaminium] butyrocarboxylate copolymer, comprising of zwitterionic carboxybetaine repeat units was synthesized via a catalyst free facile polycondensation approach. The polymer was studied for its photoluminescence, thermal, and swelling behavior. Swelling behavior was investigated in different solvent mixtures as well as in pure solvents. The extent of swelling was dictated by solvent composition, such as dielectric constant, pH, ionic strength, and other variables for instance, temperature and crosslinking density. Gel was soluble in alkali and could be regenerated on treatment with an acid. This pH responsive behavior could find various industrial applications, especially in wastewater treatment. A preliminary study on sorption of dyes was also carried out. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Equilibrium swelling properties of a novel ethylenediaminetetraacetic dianhydride (EDTAD)-modified soy protein hydrogel

A novel pH and ionic strength-sensitive protein-based hydrogel was synthesized via cross-linking ethylenediaminetetraacetic dianhydride-modified soy protein isolate (EDTAD–SPI) with glutaraldehyde. Incorporation of ionizable carboxyl groups into soy proteins increased the net negative charge of the protein and caused extensive unfolding of the protein structure. The EDTAD–SPI hydrogel was capable of imbibing 80-300 g water per g dry gel after centrifuging at 214g, depending on the extent of modification, protein structure, crosslinking density, protein concentration during the crosslinking step, gel particle size, and environ-mental conditions, such as temperature, pH, and ionic strength. The protein concentration used during the crosslinking step was found to be the most important factor affecting the water uptake of the gel. The lower the protein concentration, the higher was the water uptake at 214g. The hydrogel was highly sensitive to pH and exhibited reversible swelling when sequentially exposed to water and 0.15M NaCl. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of superabsorbent hydrogels composites based on polysuccinimide

A kind of novel superabsorbent hydrogel with high swelling ratio property that could be used for the development of water absorbing resin, soil water retention agent, and chemical sand‐fixing material was synthesized in this study. The hydrogels were prepared by the crosslinking reaction of polysuccinimide (PSI). The relationships between swelling ratio and volume of solvent as well as the concentration of crosslinking agent were investigated in detail. Several composites, such as starch, carrageenan, and polyacrylamide, were added into hydrogels to enhance the swelling ratio. It was found that the swelling ratio was significantly increased, which the maximum water absorbency was enhanced 2.46 times when the composite polyacrylamide (PAM) was added compared to the control. The effects of ionic strength and sensitivity of pH on hydrogels were also studied. The modified hydrogels products with swelling ratio less sensitivity to the salinity as well as relative high swelling ration in salinity system were also obtained by adding PAM. Through the Fourier transform infrared spectroscopy (FTIR) characterizations, the crosslinking reaction mechanism and the structure of composite were proposed. In addition, the transmission electron microscopy (TEM) examinations showed that some composite materials elevated the physical crosslinked and connected channels density substantially. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 550–557, 2006     

温度敏感高分子水凝胶的合成及性能研究

从分子设计的角度出发,选用具有优良温敏性的N-异丙基丙烯酰胺(NIPA)为基本原料,制备了温度敏感水凝胶,系统研究了水凝胶的基本物理性能(密度、平均分子量、交联密度、平衡态水含量、固定电荷密度等),测试了水凝胶在不同离子强度下的溶胀、退溶胀性能,并对其响应机理进行了探讨,同时对水凝胶的机械性能进行了测试.结果表明:温度敏感水凝胶的溶胀受离子强度和温度的影响很大,离子强度越高,溶胀率越低;其机械强度随温度变化显著.     

Biomineralized hyaluronic acid/poly(vinylphosphonic acid) hydrogel for bone tissue regeneration

Novel biomineralized hydrogels composed of hyaluronic acid (HA) and vinyl phosphonic acid (VPAc) were designed with the aim of developing a biomimetic hydrogel system to improve bone regeneration by local delivery of a protein drug including bone morphogenetic proteins. We synthesized crosslinked hydrogels composed of methacrylated HA and poly(VPAc) [P(VPAc)], which serves as a binding site for calcium ions during the mineralization process. The HA/P(VPAc) hydrogels were biomineralized by a urea‐mediation method to create functional polymer hydrogels that can deliver the protein drug and mimic the bone extracellular matrix. The water content of the hydrogels was influenced by the HA/P(VPAc) composition, crosslinking density, biomineralization, and ionic strength of the swelling media. All HA/P(VPAc) hydrogels maintained more than 84% water content. Enzymatic degradation of HA/P(VPAc) hydrogels was dependent on the concentration of hyaluronidase and the crosslinking density of the polymer network within the hydrogel. In addition, the release behavior of bovine serum albumin from the HA/PVPAc hydrogels was mainly influenced by the drug loading content, water content, and biomineralization of the hydrogels. In a cytotoxicity study, the HA/P(VPAc) and biomineralized HA/P(VPAc) hydrogels did not significantly affect cell viability. These results suggest that biomineralized HA/P(VPAc) hydrogels can be tailored to create a biomimetic hydrogel system that promotes bone tissue repair and regeneration by local delivery of protein drugs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41194.     

Effect of gelatin on the swelling behavior of organic hybrid gels based on N‐isopropylacrylamide and gelatin

Organic hybrid gels based on poly(N‐isopropylacrylamide) and a natural polymer, gelatin, were prepared through two‐step crosslinking with genipin or glutaraldehyde. The effects of the gelatin content on the swelling behaviors and physical properties of these hybrid gels were investigated. The results indicated that the swelling ratio decreased with an increase in the content of gelatin in these hybrid gels. The swelling ratio for the gel crosslinked by genipin was significantly smaller than that for the gel crosslinked by glutaraldehyde. The results also showed that the gel crosslinked with genipin had a higher crosslinking density and a higher gel strength. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1092–1099, 2005     

Theoretical and experimental investigation of the swelling behavior of sodium polyacrylate superabsorbent particles

Sodium polyacrylate superabsorbent polymers were prepared in particle forms by the inverse suspension technique. The surfactant concentration effect on the polymer particle size was analyzed with molecular sieves and an optical microscope. Water absorption and desorption characteristics were analyzed by the gravimetric method. The equilibrium water uptake in sodium polyacrylate particles was strongly dependent on both the salt concentration of the aqueous media and the crosslinking density of the polymers. The polymer crosslinking density was determined from the measurement of Young's modulus and the polymer–solvent interaction parameter from the equilibrium swelling experiment. The degree of inonization was predicted from experimental measurements, and theoretical analysis was performed on the effects of the salt concentration and polymer crosslinking density on the equilibrium water swelling ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 252–257, 2003     

Swelling behaviors of polyacrylate superabsorbent in the mixtures of water and hydrophilic solvents

The swelling behaviors of polyacrylate superabsorbent in the mixtures of water and hydrophilic solvents, including methanol, ethanol, ethylene glycol, glycerol, acetone, dimethyl formamide, and dimethyl sulfoxide, were investigated. In 20 wt % solvent–water mixture, the superabsorbent with granularity between 40‐ and 80‐mesh could reach swelling equilibrium at 25°C in several hours. It was also found that mixture temperature between 15 and 35°C had little influence on absorbency. Furthermore, the influence of water temperature between 0.5 and 99°C on absorbency was also rather limited when the superabsorbent was swelled by distilled water. The mixture concentration influenced absorbency significantly by changing the solubility parameter of the solvent–water mixture, particularly when the solubility parameter of the solvent–water mixture was < 20. The equilibrium absorbency was very high when the solubility parameter of the mixture was > 20, whereas the absorbing capacity of the superabsorbent was very low when the solubility parameter was < 17.5. The polarity fraction of solvents did not have any obvious influence on equilibrium absorbency, but not enough polarity fraction might affect the absorbing rate. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1331–1338, 2000     

Characterization,mechanical, and thermal properties of gamma irradiated starch films reinforced with mineral clay

Composite fabricated from starch and different concentrations of clay was prepared by solution casting method. The casted film was irradiated to different gamma irradiation doses 10, 20, 30, and 40 kGy. The dispersion of clay into starch was investigated by using X‐ray diffraction (XRD). The structural morphology of the composite was measured by scanning electron microscope and infrared spectroscopy. Film properties, such as water vapor transmission, mechanical, and thermal properties were also measured. The gel content and swelling behavior of the starch/clay composite were investigated. It was found that the gel content increases with increasing clay content and irradiation dose. The results obtained indicate that the starch/clay composite showed an increase in the tensile strength, thermal stability. Moreover, there is a decrease in water vapor transmission (WVRT) which improves its barrier properties. Both XRD and infrared spectroscopy showed that starch can be intercalated into the clay galleries. Also antibiotic drug Chlortetracycline HCl was loaded into the starch/clay composite by direct adsorption method. Chlortetracycline HCl adsorption capacity of composite was found to increase from 1.13 to 4.20 mg Chlortetracycline HCl per gram dry film with increasing amount of drug concentration. In vitro drug release studies in different buffer solutions showed that the basic parameters affecting the drug release behavior of the film are pH of the solution, drug concentration, and time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

On the swelling of polychloroprene-MMT nanocomposite films

For the first time, the effects on the percentage of swelling of fifteen solvents on latex polychloroprene (CR) nanocomposite (NC) films, and typical physical properties were studied. These films were prepared with 2.5, 5.0, 7.5, and 10.0 phr of montmorillonite (MMT) dispersed in water. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) results exhibit both exfoliated and intercalated layers in NC films. It was found that the Young's modulus and hardness increased with the MMT content. Calculations of the crosslink density were used to evaluate the effect of MMT concentration on the percentage of swelling. It was observed that in chloroform CR films showed the maximum swelling and it is therefore the best solvent to calculate the Flory–Huggins polymer–solvent interaction parameter as well as the crosslink density. To find the Flory-Huggins polymer–solvent interaction parameter, it was preferred to use the Hoftyser and Van Krevelen polychloroprene solubility parameter of 19.2 (MPa)^1/2 (calculated from the molar attraction constants) instead of using the swelling master curve which is not accurate. In all NC films, swelling by organic solvents was reduced by the addition of MMT. The increasing crosslink density with MMT suggests that dispersed clay emulates chemical bonds by hindering solvent migration throughout the polymer matrix and reducing solvent penetration. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of intercalated hydrotalcite on swelling and mechanical behavior for poly(acrylic acid‐co‐N‐isopropylacrylamide)/hydrotalcite nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from acrylic acid (AA), N‐isopropylacrylamide (NIPAAm), and intercalated hydrotalcite (IHT) by photopolymerization. The influence of the intercalating content of 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) in HT on the swelling and mechanical properties for poly(AA‐co‐NIPAAm)/IHT nanocomposite hydrogels was investigated. The results showed that the higher the content of the AMPS‐HT was, the higher the swelling ratio of the gels and the higher the content of the intercalating agent was, the lower swelling ratio. It was also demonstrated that the swelling ratio of the gel was not affected by the counterion in HT. The gel strength and crosslinking density were not enhanced by adding AMPS‐HT into the gel composition, but the maximum effective crosslink density and shear modulus of the nanocomposite hydrogels were increased with an increase of the content of the intercalating agent in HT. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1572–1580, 2005     

Interaction of richlocain with some linear and crosslinked polymers

The interaction of local anesthetic drug richlocain with linear polyacrylic acid and crosslinked sodium polyacrylate, linear and crosslinked acrylic acid-Schiff base copolymers has been investigated. The compositions of forming polymer-drug complexes were determined. The influence of external factors such as pH, ionic strength, temperature and thermodynamic quality of solvent on the stability of these complexes was studied. The kinetics and activation energy of drug release from the gel matrix has been evaluated.     

Studies on poly(acrylic acid)/attapulgite superabsorbent composites. II. Swelling behaviors of superabsorbent composites in saline solutions and hydrophilic solvent–water mixtures

The effect of the attapulgite content on the swelling for a series of poly(acrylic acid)/attapulgite superabsorbent composites in water was studied. The effects of the temperature and pH values on the water absorbency of the superabsorbent composites were investigated. The swelling behavior of the superabsorbent composites in various saline solutions was also investigated. The water absorbency in various salt solutions decreased with an increase in the ionic strength of the solutions. At a high ionic strength (>1 × 10^?3M), the water absorbency in monovalent cationic solutions was higher than that in multivalent cation solutions. This dramatic reduction of the water absorbency in multivalent cationic solutions of high ionic strength may have been due to the complexing ability of the carboxylate groups inducing the formation of intramolecular and intermolecular complexes, which resulted in an increased crosslink density of the network. The swelling behavior of the superabsorbent composites in mixtures of water and hydrophilic solvents, including methanol, acetone, ethanol, and dimethyl sulfoxide (DMSO), was also investigated. The water absorbency decreased with an increase in the concentration of any of the four organic solvents, and two transitions were observed in the superabsorbent composite/hydrophilic solvent–water mixture systems. The main transition for the four hydrophilic solvent–water mixtures was a collapse of the swollen gel (at 50–80% methanol, 30–80% acetone, 50–80% ethanol, and 50–80% DMSO). For the methanol–water system, the magnitudes of the first and second transitions for the poly(acrylic acid)/attapulgite superabsorbent composites containing lower proportions of attapulgite were larger than those for the superabsorbent composites with higher attapulgite contents. The effect of the mixture temperature on the water absorbency of the superabsorbent composites in 10 min was also reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1869–1876, 2004