Maximum Equilibrium Swelling Research Articles

Preparation of poly (vinyl alcohol)/polydopamine/tannin acid composite hydrogels with dual adhesive, antioxidant and antibacterial properties

Sometimes traditional hydrogel dressings for wound repair were difficult to meet the needs of use due to insufficient adhesive, antibacterial and antioxidant properties, so a high-performance and multifunctional poly(vinyl alcohol)-based hydrogel dressing was prepared using poly (vinyl alcohol) (PVA), polydopamine (PDA), and tannic acid (TA) for dual adhesive, antibacterial, and antioxidant properties in this study. The structure and morphology of the hydrogel were analyzed by FTIR and SEM. The effects of the concentrations of PVA, PDA and TA on the swelling, antioxidation and adhesion of the hydrogel were investigated. The results showed that the maximum equilibrium swelling of the hydrogels were all below 6 %, and they had good anti-swelling effects in different solution environments. The maximum skin adhesive strength of the hydrogels was 75.7 kPa, and the scavenging efficiencies against free radicals were above 90 %. Due to the inherent bacteriostatic ability of TA and the good photothermal conversion efficiency of PDA, the hydrogels could inhibit E. coli and S. aureus up to 99 %. The hydrogels possessed excellent dual antioxidant, antibacterial and adhesive properties, which greatly broadened the applications of PVA composite hydrogels.

Preparation and characterization of rapid temperature responsive cationic comb-type grafted POE-POP based hydrogel as prospective excellent actuators/sensors

In this study, novel temperature and pH–sensitive comb-type grafted (CH) poly(oxyethylene) (POE)- poly(oxypropylene) (POP) based hydrogels were prepared via epoxy ring-opening reactions. The prepared hydrogels were characterized using Fourier-transform infrared (FTIR) and differential scanning calorimetry (DSC) techniques. The thermo- and pH- responsiveness of the hydrogels was investigated by swelling experiments at the temperature of 4–50 °C and pH 5.0, 7.4 and 10.0, respectively. The desirable performance of the hydrogels was tested following swelling and deswelling kinetics at 4 and 37 °C, respectively, for all investigated pH values. According to the obtained results, the maximum equilibrium swelling of the prepared comb-type hydrogel was determined at 4 °C and pH 5.0. Comparatively to normal-type (NH) hydrogels that have same the oxypropylene ratio with CH, temperature dependence of the prepared CH hydrogels depicted faster deswelling rate than NH with no significant difference in pH dependency. The in-vitro drug-release study of the prepared POE-POP based hydrogels was performed with the model drug neomycin when the environmental temperature was changed. The findings indicated that neomycin was released even faster than the NH hydrogel from the CH hydrogels. The current finding reveals the rapid response rate properties possessed by the synthesized novel comb-typed POE-POP hydrogel, which can broaden the development of smart sensors/actuators in tissue engineering and drug delivery systems.

Preparation and characterization of environmentally friendly agar/κ-carrageenan/montmorillonite nanocomposite hydrogels

In the present study, for the first time, agar/κ-carrageenan and agar/κ-carrageenan/montmorillonite hydrogel materials were prepared by the free-radical crosslinking reaction of agar and κ-carrageenan in the presence of triethylene glycol divinyl ether (TEGDE) as the crosslinker agent. Here, montmorillonite (MMT) modified with phenylalanine was used as additive agent. Agar/κ-carrageenan hydrogel materials with and without MMT were characterized by FTIR, SEM and XRD analyses. The effect of free radical initiator (ammonium persulfate, APS) concentration, crosslinking agent (TEGDE) concentration, reaction temperature, polysaccharide ratio and MMT concentration on the swelling performance and surface property of hydrogel material was investigated and optimum reaction conditions were determined. Maximum equilibrium swelling capacity of the agar/κ-carrageenan hydrogel was found to be 2523 % under the optimum conditions ([APS] = 5 × 10−4 M, [TEGDE] = 5 × 10−4 M, T = 70 °C and magar:mκ-carrageenan = 1:4). An increase of the MMT content within hyrogel matrix led to a decrease in the swelling values of hydrogels. All of the hydrogels prepared in various formulations exhibited non-Fickian swelling behavior. New hydrogel materials obtained from this study could be potential candidates for biomedical applications.

Effect of the synthesis solvent in swelling ability of polyacrylamide hydrogels

A series of polyacrylamide hydrogels (PAAm HGs) and polymers were synthesized by free radical polymerization in the same reaction conditions but using two different media as solvent: water/ethanol at 100/0, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, and 20/80 (V/V) and water/DMSO at 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70 and 20/80 (V/V). In most cases hydrogels were obtained in high yields and their swelling degree showed a significant dependence with the solvent used in the synthesis. When HGs were synthesized in water/ethanol mixture, the maximum equilibrium swelling (Seq) was reached when the water/ethanol ratio was 60/40(V/V), while for water/DMSO it was obtained for a water/DMSO ratio 80/20. In both cases, these swelling values were higher than when the HGs were synthesized in pure water. The swelling degree achieved by the HGs in water/ethanol was directly related to the yields and the pore size, but this behavior was not observed for the HGs obtained in water/DMSO. In all cases the HGs obtained in water/DMSO swell more than those obtained in water/ethanol. On the other hand, the molar mass of the PAAm polymers prepared in the same reaction conditions, decrease as the proportion of ethanol or DMSO increase. However, the molar mass reached by the polymers obtained in water/DMSO were higher than those obtained in water/ethanol.

Effect of vinyl montmorillonite on the physical, responsive and antimicrobial properties of the optimized polyacrylic acid/chitosan superabsorbent via Box-Behnken model

This work aims to study the effect of a vinyl-modified montmorillonite (VMT) on the physical and antimicrobial properties of chitosan-graft-polyacrylic acid superabsorbent (Ch-g-PA). Ch-g-PA was first optimized using Box-Behnken design to obtain the maximum equilibrium swelling, and the model was efficient to express the experimental swelling data (R2 = 0.999). VMT was further added to the optimized Ch-g-PA in different contents 0, 4, 7 and 10 wt%. FTIR confirmed the successful synthesis of the copolymers and their nanocomposites. Morphology and the average pores size were studied using SEM. Wide angle X-ray diffraction showed the formation of exfoliated nanocomposites after VMT addition. Thermal stability studied by TGA was greatly enhanced in the presence of VMT. The swelling kinetics by Voigt-based viscoelastic model showed that the equilibrium swelling was increased by increasing the VMT up to 7 wt% then decreased after further incorporation. The superabsorbents exhibited salt and pH-responsive properties and showed a pH-reversibility at two buffer solutions (pH = 2 and pH = 9). Moreover, the prepared superabsorbents exhibited a strong bacterial and fungal killing ability which becomes more pronounced upon increasing the VMT content. The obtained results encourage the usage of the prepared copolymer nanocomposites in many fields as antimicrobial superabsorbents of improved physical properties.

Optimization of synthesis condition for carboxymethyl cellulose‐based hydrogel from rice straw by microwave‐assisted method and its application in heavy metal ions removal

AbstractBACKGROUNDAn alternative carboxymethyl cellulose‐based biosorbent hydrogel was synthesized by grafting 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) onto the prepared carboxymethyl cellulose backbone via microwave heating. Response surface methodology was employed to optimize the hydrogel synthesis condition for maximum gel content with respect to AMPS dose, N,N′‐methylene‐bis‐acrylamide dose, and microwave exposure time. The prepared gels were then characterized and evaluated in terms of their heavy metal ions adsorption performance and reusability.RESULTSThe optimum synthesis condition yielded the maximum gel content and maximum equilibrium swelling of 96.33% and 2819 ± 15%, respectively. The Langmuir model fitted the experimental isotherm data well, with maximum adsorption capacity of 86.21, 102.04 and 33.56 mg g‐1 for Cu2+, Pb2+ and Fe3+, respectively. Microwave heating was clearly noted to result in hydrogel of higher porosity and could shorten the synthesis time by 88.33%; the gel content was 7.46% higher compared with that obtained via conventional heating.CONCLUSIONMicrowave‐assisted heating is a feasible alternative and an efficient technique for CMC‐g‐AMPS hydrogel synthesis. The optimized CMC‐g‐AMPS hydrogel exhibited good performance for Cu2+, Pb2+ and Fe3+ ions removal and was satisfactorily reused, thus contributing to the alleviation of environmental problems caused by discarded rice straw and water contaminated with heavy metal ions. © 2017 Society of Chemical Industry

Dynamic swelling behavior of interpenetrating polymer networks in response to temperature and pH.

Temperature responsive hydrogels based on ionic polymers exhibit swelling transitions in aqueous solutions as a function of shifting pH and ionic strength, in addition to temperature. Applying these hydrogels to useful applications, particularly for biomedical purposes such as drug delivery and regenerative medicine, is critically dependent on understanding the hydrogel solution responses as a function of all three parameters together. In this work, interpenetrating polymer network (IPN) hydrogels of polyacrylamide and poly(acrylic acid) were formulated over a broad range of synthesis variables using a fractional factorial design, and were examined for equilibrium temperature responsive swelling in a variety of solution conditions. Due to the acidic nature of these IPN hydrogels, usable upper critical solution temperature (UCST) responses for this system occur in mildly acidic environments. Responses were characterized in terms of maximum equilibrium swelling and temperature-triggered swelling using turbidity and gravimetric measurements. Additionally, synthesis parameters critical to achieving optimal overall swelling, temperature-triggered swelling, and sigmoidal temperature transitions for this IPN system were analyzed based on the fractional factorial design used to formulate these hydrogels.

Synthesis, Characterization, and swelling behaviors of acrylic acid/carboxymethyl cellulose superabsorbent hydrogel by glow‐discharge electrolysis plasma

This article exploits a new approach for synthesis of acrylic acid/carboxymethyl cellulose (AA/CMC) superabsorbent hydrogel in aqueous solution by a simple one‐step using glow‐discharge electrolysis plasma, in which N,N′‐methylenebisacrylamide (MBA) was used as a crosslinking agent. The reaction parameters affecting the equilibrium swelling, that is, discharge voltage, discharge time, mass ratio of AA to CMC, content of crosslinker, and degree of neutralization, were systematically optimized to achieve a superabsorbent hydrogel with a maximum equilibrium swelling. The structure, thermal stability, and morphology of AA/CMC superabsorbent hydrogel were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The swelling kinetics in distilled water and swelling behaviors in various pH solutions and salts solutions (NaCl, KCl, MgCl2, CaCl2, AlCl3, and FeCl3) were investigated in detail. The effect of six cationic salt solutions on the equilibrium swelling had the following order K+ > Na+ > Mg2+ > Ca2+ > Al3+ > Fe3+. In addition, the pH‐reversibility was preliminarily investigated with alternating pH between 6.5 and 2.0. The results showed that the equilibrium swelling of AA/CMC was achieved in 90 min. The hydrogel was responsive to the pH and salts, and was reversible swelling and deswelling behavior. POLYM. ENG. SCI., 54:2310–2320, 2014. © 2013 Society of Plastics Engineers

High strength poly(acrylamide)-clay hydrogels

A series of polyacrylamide nanocomposite hydrogels were synthesized by in situ free radical polymerization of acrylamide (AAm) with ethylene glycol dimethacrylate (EGDMA) as a crosslinker in the presence of sodium montmorillonite (NaMMT) and organically modified montmorillonite (OrgMMT) clays. Modification of MMT was carried out with a quaternary salt of coco amine as intercalant having a styryl group whose contribution to both polymerization and crosslinking reactions via its reactive double bond was confirmed by solid state NMR. Exfoliation success was checked with X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques whereas mechanical performance was followed with uniaxial compression experiment. It has been found that exfoliated PAAm nanocomposites having 0.5% OrgMMT had both the maximum equilibrium swelling in water and compression strength as well as improved thermal stability due to the special and beneficial morphology observed via scanning electron microscopy (SEM).

Preparation and swelling behavior of macroporous poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels

AbstractMacroporous superabsorbent hydrogels (SAHs) composed of acrylamide (AAm) and sodium methacrylate (NMA) were prepared by aqueous solution polymerization in the presence of a glucose solution. Their swelling capacity was investigated as a function of the concentrations of the glucose solution, sodium methacrylate, crosslinker, initiator, and activator. The porosity of the poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels was confirmed using scanning electron microscopy. The SAHs were characterized by IR spectroscopy. To estimate the effect on the swelling behavior, three types of crosslinkers were employed: N,N′‐methylenebisacrylamide, 1,4‐butanediol diacrylate, and diallyl phthalate. Network structural parameters such as initial swelling rate, swelling rate constant, and maximum equilibrium swelling were evaluated by water absorption measurement. The equilibrium water content (EWC%) of the AAm–NMA macroporous SAHs was found to be in the range of 93.31–99.68, indicating that these SAHs may have applications as biomaterials in the medicinal, pharmaceutical, and veterinary fields. Most of the SAHs prepared in this investigation followed non‐Fickian‐type diffusion, and few followed a case II– or super–case II‐type diffusion. The diffusion coefficients of these macroporous SAHs were investigated. Further, the swelling behavior of these SAHs also was investigated at different pHs and in different salt solutions and simulated biological fluids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3202–3214, 2006

Polymer composition and acidification effects on the swelling and mechanical properties of poly(acrylamide-co-acrylic acid) superporous hydrogels

Poly(acrylamide-co-acrylic acid) (poly(AM-co-AA)) superporous hydrogels (SPHs) were synthesized and the acidification effects on the swelling and mechanical properties were studied. Gelation exotherms were measured to determine the optimum introduction time for adding a blowing agent. The gelation kinetics decreased with increasing the AA concentration. The maximum equilibrium swelling was observed around an AA weight fraction of 0.4, but the compressive strength decreased monotonically with increasing the AA concentration. Poly(AM-co-AA) SPHs were much less swollen in acidic solution than in distilled water of pH 6.7. The swelling ratio decreased with increasing acidity (decreasing pH). Reduction of water absorption content by acidification led to considerable increase in the mechanical strength.

Poly(hydroxamic acid) hydrogels from poly(acrylamide): preparation and characterization

Poly(hydroxamic acid) (PHA) hydrogels from crosslinked poly(acrylamide) (PAAm) hydrogels containing different type crosslinkers such as such as N, N'-methylene bisacrylamide (N) and ethyleneglycol dimethacrylate (E). The effect of crosslinkers on some physical properties was investigated. The structure of hydrogels was characterized spectroscopically and thermally. The swelling parameters of PHA in distilled water, such as percent equilibrium swelling (Seq%), initial swelling rate (ro), maximum equilibrium swelling (Smax), diffusional exponent (n), network parameter (k) and diffusion coefficient (D) were calculated. It has been found that the ionogenity of PHA and the structure of the used crosslinkers during the synthesis have been effective on the swelling behaviour of the hydrogels.

Controlled release of aminophylline from poly (N‐isopropylacrylamide‐co‐itaconic acid) hydrogels

AbstractN‐Isopropylacrylamide (NIPA) has been copolymerized with itaconic acid (IA) in the presence of N,N‐methylenebisacrylamide (BIS) as crosslinker. The swelling capacity and the release rate of aminophylline at 37 °C are reported. Maximum equilibrium swelling increases as the itaconic acid content in the hydrogel increases. The experimental data suggest clearly that the swelling process obeys second‐order kinetics. According to this, the kinetic constant, k, and the maximum equilibrium swelling, W∞, have been calculated. Drug release from fully swollen hydrogels follows Fick's law closely, but deviates from it for xerogels.© 2001 Society of Chemical Industry