Methylenebisacrylamide Content Research Articles

Chitosan-based intelligent polymeric networks for site-specific colon medication delivery: A comprehensive study on controlled release of diloxanide furoate and network formation dynamics

Oral medications are prone to gastric degradation and enzymatic inactivation, diminishing their efficacy. This study investigates a solution by developing intelligent polymeric networks, incorporating chitosan, methacrylic acid, N, N, methylene bisacrylamide, and montmorillonite clay, to enable the controlled release of Diloxanide Furoate (DF), an anti-protozoal drug. Employing a swelling-assisted diffusion technique, drug loading percentages varied from 63.96 % to 76.82 % among different formulations. Increased chitosan and methacrylic acid content enhanced drug loading, while N, N, methylene bisacrylamide and montmorillonite clay demonstrated an inverse relationship affecting diffusion and swelling.Equilibrium swelling studies unveiled formulation-dependent behaviors, with chitosan reducing swelling and methacrylic acid promoting it. Higher N, N, methylene bisacrylamide concentrations decreased swelling, indicating a denser cross-linked structure, while montmorillonite clay reduced hydrophilicity and swelling capacity. Further analyses confirmed successful gel formation, particularly in formulations with higher chitosan, methacrylic acid, and N, N, methylene bisacrylamide content, while montmorillonite clay limited gel fraction due to restricted polymer chain mobility. Techniques such as Fourier transform infrared spectroscopy, Differential scanning calorimetry, and thermal gravimetric analyses supported network development, enhancing thermal stability and cross-linking density. This research underscores the flexibility of polymeric networks for precise drug delivery, offering potential advancements in targeted therapies for various medical conditions.

Novel Natrosol/Pectin-co-poly (acrylate) based pH-responsive polymeric carrier system for controlled delivery of Tapentadol Hydrochloride

Background & ObjectivesThis study aimed to create a controlled delivery system for Tapentadol Hydrochloride by developing interpenetrating networks (IPNs) of Natrosol-Pectin copolymerized with Acrylic Acid and Methylene bisacrylamide, and to analyze the effects of various ingredients on the physical and chemical characteristics of the IPNs. MethodsNovel Tapentadol Hydrochloride-loaded Natrosol-Pectin based IPNs were formulated by using the free radical polymerization technique. Co-polymerization of Acrylic Acid (AA) with Natrosol and Pectin was performed by using Methylene bisacrylamide (MBA). Ammonium persulfate (APS) was used as the initiator of crosslinking process. The impact of ingredients i.e. Natrosol, Pectin, MBA, and Acrylic Acid on the gel fraction, porosity, swelling (%), drug loading, and drug release was investigated. FTIR, DSC, TGA, SEM and EDX studies were conducted to confirm the grafting of polymers and to evaluate the thermal stability and surface morphology of the developed IPNs. ResultsSwelling studies exhibited an increase in swelling percentage from 84.27 to 91.17% upon increasing polymer (Natrosol and Pectin) contents. An increase in MBA contents resulted in a decrease in swelling from 85 to 67.63%. Moreover, the swelling was also observed to increase with higher AA contents. Significant drug release was noted at higher pH instead of gastric pH value. Oral toxicological studies revealed the nontoxic and biocompatible nature of Natrosol-Pectin IPNs. Interpretation & ConclusionThe developed IPNs were found to be an excellent system for the controlled delivery of Tapentadol Hydrochloride.

Effect of crosslinker to monomer ratio on the adhesion and size distribution of silver nanoparticles grown on poly (methacrylic acid) microspheres

In this study poly methacrylic acid (MAA) microparticles were synthesized with variations in methylene-bis-acrylamide (MBA), with MBA in the role of the crosslinker. The as produced microparticles serve as substrates for the growth of silver nanoparticles while evaluating the effect of different crosslinker content. Each formulation was assessed in terms of silver nanoparticle adhesion, size distribution and silver quantity. Experimental evidence reveals that while incorporating crosslinker above 20 wt% with respect to the monomer, silver nanoparticle adhesion to the polymer surface increases, whereas in formulations above 35 wt% microparticle morphology hinders silver ion binding and the subsequent formation of silver nanoparticles. In addition, TEM microcopy combined with image classification analysis reported that in the range of 20–35 wt% MBA content, silver nanoparticle size distribution can be tuned. Evidently, MBA content between 20 wt% and 35 wt% (in relation to MAA) exhibits a dynamic state where carboxylic acid terminated functional side groups and amino-terminal side groups provide a synergistic effect in silver ion binding thus opening a functional pathway towards the controlled synthesis of silver nanoparticles.

High‐strength, ultrastretchable hydrophobic association hydrogel reinforced by tailored modified carboxymethyl cellulose

AbstractA new pathway to construct high‐strength, ultrastretchable hydrogels based on tailored modified carboxymethyl cellulose (TMCMC)and hydrophobic association(HPA) system was investigated. TMCMC was prepared from degradation of carboxymethyl cellulose (CMC)/N,N′‐methylene bisacrylamide (MBA) chemical cross‐linked hydrogels. The residual double bonds of TMCMC, confirmed by 1H‐NMR and FTIR analysis, reacted with acrylamide in HPA to form TMCMC/HPA hydrogels, and the homogeneous and fine spatial network structure of TMCMC/HPA hydrogel could be observed by scanning electron microscopy. Rheological analysis revealed that the coexistence of physical and chemical crosslinking in TMCMC/HPA hydrogels. Further studies showed that TMCMC/HPA hydrogel with MBA content of 0.5 wt% has outstanding mechanical properties, and its fracture stress, elongation and tensile strength reach 1.17 MPa, 3717.05% and 15.68 MJ·m−3, respectively. Moreover, the hydrogel displayed good swelling resistance and stable strain electrical signal response.

Feasibility of thermo-sensitive P(NIPAM-MBA) hydrogels as novel stripping agents for osmotic membrane distillation

As thermo-sensitive hydrogels could absorb water quickly and squeeze the water out by their insoluble cross-linked networks under thermal stimulus, a novel osmotic membrane distillation (OMD) process was proposed for the first time. In the OMD process of this study, water vapor diffused across the membrane under the swelling pressure of thermo-sensitive hydrogels. Poly-N-isopropylacrylamide (PNIPAM) hydrogels with 0.02%, 0.1% and 0.5% N,N′-methylenebisacrylamide (MBA) were synthesized and incorporated into the OMD system. The hydrogel properties were characterized by UV–vis spectrophotometer, FTIR and SEM. The effects of MBA content, membrane characteristics, operating temperature on OMD flux were investigated. The initial fluxes for the 0.02%, 0.1% and 0.5% MBA hydrogel-OMD systems were 1.68, 1.09 and 0.76 kg/m2·h, respectively. And the hydrogels transformed to dehydrated state after 150 min of water absorption. The fastest water absorption rates for PNIPAM hydrogels with 0.02%, 0.1% and 0.5% MBA were obtained at the initial swelling ratios of 16, 14 and 12 folds, respectively. Besides, the optimal feed temperatures for the maximum flux were 40 °C, 50 °C and 50 °C for hydrogels with 0.02%, 0.1% and 0.5% MBA, respectively. The membranes with higher porosity and lower thickness demonstrated higher fluxes. According to our results, the swelling pressure of hydrogel acted as a driving force of the hybrid hydrogel-OMD system, and it was greatly affected by the hydrogel structure. Typically, a hydrogel with the balanced water absorbing and dewatering behaviors and a membrane with good mass transfer performance were two essential prerequisites for this process.

Preparation of nanogels based on kappa-carrageenan/chitosan and N-doped carbon dots: study of drug delivery behavior

In this study, new pH-sensitive nanogels containing rivastigmine as a model drug were synthesized by graft polymerization of Acrylamid/Sodium Acrylate monomers onto chitosan (CS) and kappa-carrageenan (CG or κ-carrageenan) backbone in the presence of N, N'-Methylenebisacrylamide (MBA) as cross-linker, nitrogen-doped carbon dots (N-CDs) and ammonium persulfate as an initiator. The prepared nanogels were characterized by FE-SEM, XRD, FTIR, EDX and TGA techniques. The swelling behavior of the nanogels was affected by MBA content, monomer content, amount of CG or CS, and pH in the synthesis. The nanogels exhibited well pH-sensitivity during drug release investigation under simulated gastric (< 61% at pH 1.2) and intestinal (~ 95% at pH 7.4) media. The cytotoxicity test was investigated on human fibroblast cells using MTT assay. The results indicated that cell survival rate was more than 88% in < 62.5 μg/mL concentration of nanogels. Incorporating of N-CDs in the nanogel network increased the swelling capacity, entrapment efficiency, and ensuring the controlled release of the entrapped drug. In this work, we were able to enhance the properties of drug-loaded chitosan nanogels in pH 7.4.

Novel biodegradable hydrogel based on natural polymers: Synthesis, characterization, swelling/reswelling and biodegradability

In order to reduce the production costs of hydrogel and decrease the negative impact on the environment, a new low-cost and eco-friendly semi-interpenetrating polymer network (semi-IPN) hydrogels of cassava starch-g-polyacrylic acid/natural rubber/polyvinyl alcohol blends (CSt-g-PAA/NR/PVA) was prepared. The hydrogel was synthesized by aqueous solution polymerization method in the presence of initiator ammonium persulfate (APS) and N,N’-methylene-bis-acrylamide (MBA) as a crosslinker. A reaction mechanism for synthesis of CSt-g-PAA/NR/PVA semi-IPN hydrogels was proposed. Factors affecting the swelling capacity, such as CSt, AA, APS and MBA contents were evaluated and optimized. The sample prepared under optimized conditions had a water absorbency of 794% in distilled water and 244% in 0.9 wt% NaCl solution. It also exhibited an excellent water retention with lower decreasing rate and were highly sensitive to the salt concentration, cation type, pH and reswelling time. The semi-IPN hydrogel demonstrated a good biodegradation with a rate of 0.626 wt%/day. It is believed that the obtained CSt-g-PAA/NR/PVA could have potential applications in agricultural areas because of their good water absorption, excellent retention capacities, high reswelling capability, and cost-effective and ecofriendly preparation.

ELECTRORESPONSIE BEHAVIOR OF POLYELECTROLYTE GELS (ACRYLIC ACID-CO-N-N' METHYLENE BISACRYLAMIDE) UNDER THE INFLUENCE OF ELECTRIC FIELD

Polymer gels which were synthesized from acrylic acid and N-N’ methylene bisacrylamide exhibited electrical sensitive behavior. Their swelling properties and electroresponsive behavior were studied. The results indicated that the water take-up ability of the hydrogel increased with the decreased N-N’ methylene bisacrylamide content within the network. The hydrogel membranes swollen in a neutral NaCl solution, bent toward the cathode under non-contact DC electric fields, and their bending speed and equilibrium strain increased with the increased of applied voltage. In addition, the effect of crosslinker concentration of N-N’ methylene bisacrylamide on bending behavior of the gels have been studied. The equilibrium strain decreased as the crosslinker concentration increased. By changing the direction of the applied potential cyclically, the hydrogel membranes exhibited good reversible bending behavior. The bending of the hydro gel membranes was initially explained by a bending theory of polyelectrolyte hydrogel based on the charge of osmotic pressure due to the ion concentration different between the inside and the outside of the network.

Synthesis and properties of biodegradable hydrogels based on cross-linked natural rubber and cassava starch

A series of interpenetrating polymer network (IPN) hydrogels based on cross-linked natural rubber (XNR) and cassava starch (CSt) as biodegradable membrane material were synthesized via free radical polymerization in latex state using N, N′-methylene bisacrylamide (MBA) and maleic acid as cross-linkers. The IPN XNR/CSt hydrogels were confirmed and characterized by infrared spectroscopy, thermal analysis, and X-ray diffraction. The results showed that with increasing MBA content from 1.0 to 2.5 phr, cross-link density and gel fraction of XNR increased from 0.80 to 0.90 mol M−3 and from 19.7% to 30.5%, respectively. The gel fraction and tensile strength of the IPN XNR/CSt hydrogels also gradually increased as a function of MBA content but the water swelling and elongation at break decreased slightly. The IPN XNR/CSt containing 1.0 phr MBA displayed the highest water swelling of 82%. The weight retentions of IPN XNR/CSt hydrogels after soil degradations for 90 days increased from 48% to 56% with increasing MBA from 1.0 phr to 2.5 phr. The IPN XNR/CSt exhibited not only a good biodegradation but also high mechanical strength and flexibility. Also, the IPN XNR/CSt could be a promising candidate as a biodegradable membrane for longer released fertilizer application.

Cross-linking as a tool for enhancement of transfection efficiency of cationic vectors

A series of nanogel particles with the growing cross-linking degree was synthesized in reverse micelles by copolymerization of a cationic monomer N,N-dimethylaminoethylmethacrylate with increasing amounts of N,N′-methylenebisacrylamide (MBA). The growth of MBA content in the studied range of 0.2–15% (mol) resulted in a regular decrease of the particles’ size with a narrowing in their size distribution which occurred at the first of the cross-linker addition. In the second region, where the MBA content was more than 5% (mol), the size distribution was very narrow. The cross-linked polymers prepared at 2–5% of the cross-linker amount demonstrated a minimum size of the polyplexes and enhancement in the transfection with plasmid DNA and small interfering RNA targeted to the luciferase gene. The revealed changes in the properties of nanogels occurring upon the changes in the cross-linking degree appear to be a platform for a controlled manufacturing of efficient cross-linked cationic vectors.

An amphoteric hydrogel: Synthesis and application as an internal curing agent of concrete

ABSTRACTA new crosslinked amphoteric hydrogel (PAC) was synthesized and evaluated as an internal curing agent of concrete. PAC was prepared from acrylamide (AM) and 4‐(2‐((carboxylatomethyl)dimethylammonio)ethoxy)−4‐oxobut‐2‐enoate (CMD) through free‐radical polymerization by using ammonium persulfate (APS) as an initiator and methylene‐bisacrylamide (MBA) as a crosslinker. The structure of the prepared polymer was verified by the IR spectra. The effects of the polymerization variables on the swelling capacity of PAC were investigated. The water absorbency of PAC was found to increase with increasing CMD/AM ratio, reach a maximum value, and decrease afterword. Increase of either APS or MBA content decreased the water absorbency. The highest water absorbency of PAC hydrogel (P7) achieved in deionized water, 0.1M NaCl solutions and 0.1M CaCl2 solutions, was 306 g/g, 32 g/g, and 22 g/g, respectively. Compared with a commercial acrylate‐based hydrogel 283HA, P7 was less sensitive to the existence of Ca2+ ions in cement pore solutions, and more effective in reducing the cracking tendency of cement pastes. Finally, mortars incorporated with proper amounts of P7 showed smaller drying shrinkage and higher compressive strength than that without hydrogel present. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42175.

Synthesis of cellulose-based superabsorbent hydrogels by high-energy irradiation in the presence of crosslinking agent

Superabsorbent hydrogels were prepared from aqueous solutions of four cellulose derivatives (carboxymethylcellulose Na-salt – CMC, methylcellulose – MC, hydroxyethylcellulose – HEC and hydroxypropylcellulose – HPC) by gamma irradiation initiated crosslinking. CMC was used for the majority of the measurements. N,N’-methylene-bis-acrylamide (MBA) crosslinking agent was used to modify the gel properties. The crosslink density increased with the MBA concentration, leading to an improved gel fraction and lower water uptake. The crosslinking efficiency was the highest up to 1 w/wpolymer% MBA concentration. Very high MBA content (10 w/wpolymer%) led to a heterogeneous gel structure. Gelation also occurred under milder conditions in the presence of MBA: good gel properties were achieved at significantly lower doses and solute concentrations as compared to crosslinker-free solutions. The time required to reach maximum water uptake increased with the degree of swelling in equilibrium. Swelling properties of CMC gels with lower water uptake showed lower sensitivity to the ionic strength of the solvent.

Antibody-Imprinted Membrane Adsorber via Two-Step Surface Grafting

In this work, a recently established, novel two-step imprinting strategy combining surface imprinting and scaffold imprinting was applied successfully to prepare a molecularly imprinted polymer (MIP) adsorber for immunoglobulin G (IgG). Track-etched polyethylene terephthalate (PET) membranes with previously introduced aliphatic C-Br groups as initiator on the pore surface were used to prepare first a functional polymer scaffold, grafted poly(methacrylic acid), via surface-initiated atom transfer radical polymerization (SI-ATRP). After template protein (IgG) binding to the scaffold, UV-initiated cross-linking copolymerization of acrylamide and methylenebisacrylamide (MBAA) as second step lead to a grafted MIP hydrogel layer. The influences of the three independent parameters, scaffold chain length by SI-ATRP time, degree of cross-linking of the MIP layer by MBAA content, and grafted MIP layer thickness by UV irradiation time, were studied to optimize protein binding capacity and selectivity. The results were also compared to previously obtained data for lysozyme imprinting using the same method, and significant effects of protein size on imprinting efficiency could be identified. The best IgG MIP membrane adsorber was then used to separate IgG from mixtures with human serum albumin (HSA), demonstrating IgG binding capacities and eluted IgG purities, which were almost independent of the excess of HSA. The results of this study are a significant extension of the scope of molecular imprinting toward large target bionanoparticles. The transfer of the approach from the model PET to other base membranes with higher specific surface area is straightforward, and the resulting affinity materials would, in principle, be suited for "capturing" of an antibody from a complex mixture.

Synthesis and Characterization of Ionic Polymer Networks in a Room-Temperature Ionic Liquid

Ionic liquid gels (ILGs) for potential use in ion transport and separation applications were generated via a free radical copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N,N'-methylene(bis)acrylamide (MBA) using 1-ethyl-3-methylimidazolium ethylsulfate (IL) as a room temperature ionic liquid solvent medium. The AMPS and MBA monomer solubility window in the IL in the temperature range of 25 to 65 °C was determined. In situ ATR-FTIR showed near complete conversion of monomers to a cross-linked polymer network. ILGs with glass transition temperatures (T(g)s) near -50 °C were generated with T(g) decreasing with increasing IL content. The elastic moduli in compression (200 to 6600 kPa) decreased with increasing IL content and increasing AMPS content while the conductivities (0.35 to 2.14 mS cm⁻¹) increased with increasing IL content and decreasing MBA content. The polymer-IL interaction parameter (χ) (0.48 to 0.55) was determined via a modified version of the Bray and Merrill equation.

Preparation and characterization of nanosized P(NIPAM-MBA) hydrogel particles and adsorption of bovine serum albumin on their surface.

Thermosensitive polymer hydrogel particles with size varying from 480 to 620 nm were prepared through precipitation copolymerization of N-isopropylacrylamide with N,N′-methylenebisacrylamide (MBA) in water with ammonium persulfate as the initiator. Only polymer hydrogels without any coagula were obtained when MBA concentration in the monomer mixture was kept between 2.5 and 10.0 wt%; with increased MBA concentration, the monomer conversion was enhanced, the size of the hydrogels was increased, and their shrinking was lessened when heated from 25°C to 40°C. Bovine serum albumin adsorption on the surface of the hydrogels of different MBA content was measured at different pH levels and under different temperatures. The results demonstrated that the adsorption of the protein on the hydrogels could be controlled by adjusting the pH, the temperature of adsorption, and the crosslinking in the hydrogels. The results were interpreted, and the mechanisms of the polymerization were proposed.

Preparation and characterization of hybrid pH-sensitive hydrogels of chitosan-co-acrylic acid for controlled release of verapamil

In the present work crosslinked hydrogels based on chitosan (CS) and acrylic acid (AA) were prepared by free radical polymerization with various feed compositions using N,N methylenebisacrylamide (MBA) as crosslinking agent. Benzoyl peroxide was used as catalyst. Fourier transform infrared spectra (FTIR) confirmed the formation of the crosslinked hydrogels. This hydrogel is formed due to electrostatic interaction between cationic groups in CS and anionic groups in AA. Prepared hydrogels were used for dynamic and equilibrium swelling studies. For swelling behavior, effect of pH, polymeric and monomeric compositions and degree of crosslinking were investigated. Swelling studies were performed in USP phosphate buffer solutions of varying pH 1.2, 5.5, 6.5 and 7.5. Results showed that swelling increased by increasing AA contents in structure of hydrogels in solutions of higher pH values. This is due to the presence of more carboxylic groups available for ionization. On the other hand by increasing the chitosan content swelling increased in a solution of acidic pH, but this swelling was not significant and it is due to ionization of amine groups present in the structure of hydrogel. Swelling decreased with increase in crosslinking ratio owing to tighter hydrogel structure. Porosity and sol-gel fraction were also measured. With increase in CS and AA contents porosity and gel fraction increased, whereas by increasing MBA content porosity decreased and gel fraction increased. Furthermore, diffusion coefficient (D) and the network parameters i.e., the average molecular weight between crosslinks (M(c)), polymer volume fraction in swollen state (V(2s)), number of repeating units between crosslinks (M(r)) and crosslinking density (q) were calculated using Flory-Rehner theory. Selected samples were loaded with a model drug verapamil. Release of verapamil depends on the ratios of CS/AA, degree of crosslinking and pH of the medium. The release mechanisms were studied by fitting experimental data to model equations and calculating the corresponding parameters. The result showed that the kinetics of drug release from the hydrogels in both pH 1.2 and 7.5 buffer solutions was mainly non-Fickian diffusion.

Preparation and characterization of poly (N-isopropylacrylamide)/polyvinylamine core-shell microgels

In this paper, well-defined temperature- and pH-sensitive core-shell microgels were synthesized by graft copolymerization in the absence of surfactant and stabilizer. The microgel particles consisted of poly (N-isopropylacrylamide (NIPAm)) core crosslinked with N, N′-methylene-bisacrylamide (MBA) and polyvinylamine (PVAm) shell. The effect of MBA content and NIPAm/PVAm ratio on microgel size was investigated. SEM showed that the microgels were spherical and had narrow particle-size distribution. TEM images of the microgels clearly displayed well-defined core-shell morphologies. Zeta-potential measurement further elucidated that the microgels possessed positively charged PVAm molecules on the microgel surface. Turbidity measurement and 1H-nuclear magnetic resonance (NMR) experiments indicated that the VPTT of microgels was the same as the LCST of PNIPAm. 1H-NMR experiments also inferred that the methyl proton of N-isopropylacrylamide appeared three peaks and responded to hydrogen-bonding interaction including polymer chain with water molecular, intramolecular interaction and intermolecular interaction, respectively.

Preliminary investigation of the NMR, optical and x-ray CT dose–response of polymer gel dosimeters incorporating cosolvents to improve dose sensitivity

This study reports on efforts to increase the dose sensitivity of polymer gel dosimeters used in 3D radiation dosimetry. The potential of several different cosolvents is investigated, with the aim of increasing the solubility of N,N′-methylene-bisacrylamide crosslinker in polymer gel dosimeters. Glycerol and isopropanol increase the limit for the crosslinker solubility from approximately 3% to 5% and 10% by weight, respectively. This enables the manufacture of polymer gel dosimeters with much higher levels of crosslinking than was previously possible. New dosimeter recipes containing up to 5 wt% N,N′-methylene-bisacrylamide were subjected to spatially uniform radiation and were studied using nuclear magnetic resonance (NMR), as well as x-ray and optical CT techniques. The resulting dosimeters exhibit dose sensitivities that are up to 2.7 times higher than measured for a typical dosimeters with 3% N,N′-methylene-bisacrylamide without the addition of cosolvent. Two additional cosolvents (n-propanol and sec-butanol) were deemed unsuitable for practical dosimeters due to incompatibility with gelatin, cloudiness prior to irradiation, and immiscibility with water when large quantities of cosolvent were used. The dosimeters with high N,N′-methylene-bisacrylamide content that used isopropanol or glycerol as cosolvents had high optical clarity prior to irradiation, but did not produce suitable optical CT results for non-uniformly irradiated gels due to polymer development outside of the high dose regions of the pencil beams and significant light scatter. Further experiments are required to determine whether cosolvents can be used to manufacture gels with sufficiently high dose sensitivity for readout using x-ray computed tomography.

Network and thermodynamic properties of hydrogels of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine

Samples of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine] (PSPV) have been synthesized to high conversion by free radical polymerization in aqueous solution of the zwitterionic monomer SPV with several concentrations of the crosslinker N, N′-methylene-bis-acrylamide (MBA). Hydrogels obtained by swelling them in water and aqueous KSCN solution were examined by gravimetric and dimensional analysis, and by compression–strain measurements. The derived effective crosslinking density ν e was only ca. 11% of the theoretical value, indicating low efficiency of chemical crosslinking by MBA. At 298 K increasing content of MBA produces increases in the values of ν e, elastic moduli and polymer–water interaction parameter χ. At a fixed MBA content, increasing temperature led to decreases in the values of ν e, elastic moduli and χ, but an increase in water content of hydrogel. For swelling in aq. KSCN solution the mechanical properties are insensitive to content of salt. Experimental and theoretical analysis afforded values of the water/polymer, salt/water and salt/polymer interaction parameters. Where appropriate the findings are compared with those reported for a different zwitterionic hydrogel and a neutral non-zwitterionic hydrogel.

Observations on the swelling characteristics of the zwitterionic hydrogel of poly(1-3-sulfopropyl)-2-vinyl-pyridinium-betaine hydrogel

Samples of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine] (PSPV) have been synthesized to high conversion by free radical polymerization in aqueous solution of the zwitterionic monomer SPV with several concentrations of the crosslinker N, N′-methylene-bis-acrylamide (MBA). The densities of the resultant xerogels increased regularly with the content of MBA. Hydrogels obtained by swelling them in water and aqueous KSCN solution were examined by gravimetric and dimensional analysis. The water contents increased with decreasing content of MBA, the value of 92.7 wt% at the lowest MBA content being higher than that for other zwitterionic hydrogels. Enhanced swelling occurred in 1 M aq. KSCN at each MBA content, the total swelling being 98.1 wt% at the lowest crosslinker content. Swelling increased with increasing temperature. An approximate procedure to formulating swelling equilibrium in term of the volume fraction of water in hydrogel, in conjunction with the van’t Hoff equation, yields a small positive value for the enthalpy of swelling. This is compared with values derived similarly for other hydrogels.