Sodium Vinyl Sulphonate is the organosulfur compound with the formula CH₂ = CHSO₃H. Sodium Vinyl Sulphonate is the simplest unsaturated sulfonic acid. The C = C double bond is the region of high reactivity. Sodium Vinyl Sulphonate gives polyvinylsulfonic acid when used as comonomer with polymerized, especially functionalized vinyl and acrylic acid compounds.
CAS NUMBER: 3039-83-6
SYNONYM :
Sodium ethenesulfonate;Sodium vinylsulfonate;3039-83-6;Sodium ethylenesulphonate;Vinylsulfonic acid sodium salt;Ethenesulfonic acid, sodium salt; Sodium Vinyl sulfonate;Sodium ethylenesulfonate;Ethenesulfonic acid, sodium salt (1:1);UNII F7K3L38Z7B;sodium;ethenesulfonate;Lyapolate sodium [USAN]; MFCD00007520;F7K3L38Z7B;25053-27-4;9002-97-5;Sodium apolate (INN); Sodium apolate [INN];Lyapolate sodium;Lyapolate sodium (USAN); Ethenesulfonic acid, sodium salt, homopolymer;NCGC00185758-01;Peson; Sodium apolate;UNII-9461405D9F;NSC 8957;EINECS 221-242-5; Ethenesulfonic acid, sodium salt (1:1), homopolymer;Sodium vinyl Sulphonate polymer;Peson (TN);sodiumethylenesulphonate
Sodyum Vinil Sülfona is the organosulfur compound with the formula CH2=CHSO3H. Sodium Vinyl Sulphonate is the simplest unsaturated sulfonic acid. The C=C double bond is a site of high reactivity. polymerize gives polyvinylsulfonic acid, especially when used as a comonomer with functionalized vinyl and (meth)acrylic acid compounds. Sodium Vinyl Sulphonate is a colorless, water-soluble liquid, although commercial samples can appear yellow or even red. Sodium Vinyl Sulphonate is produced industrially by the alkaline hydrolysis of carbyl sulfate with subsequent acidification of the resulting vinyl sulfonate salt The reaction is highly exothermic (reaction enthalpy: 1,675 kJ/kg) and requires exact maintenance of temperature and pH during the hydrolysis. When calcium hydroxide is used as the hydrolysis medium, a solution of calcium vinyl sulfonate is obtained. Acidification of this hydrolysis mixture with sulfuric acid gives Sodium Vinyl Sulphonate, together with the poorly soluble calcium sulfate. Sodium Vinyl Sulphonate also can be prepared by dehydration of isethionic acid with phosphorus pentoxide
Sodium Vinyl Sulphonate can also be prepared by sulfochlorination of chloroethane, dehydrohalogenation to vinylsulfonyl chloride and subsequent hydrolysis of the acid chloride. The activated C=C double bond of Sodium Vinyl Sulphonate reacts readily with nucleophiles in an addition reaction. 2-Aminoethanesulfonic acid is formed with ammonia and 2-methylaminoethanesulfonic acid with methylamine. Sodium Vinyl Sulphonateis the monomer in the preparation of highly acidic or anionic homopolymers and copolymers. These polymers are used in the electronic industry as photoresists, as ion-conductive polymer electrolyte membranes (PEM) for fuel cells. For example, transparent membranes with high ion exchange capacity and proton conductivity can be produced from polyvinylsulfonic acid. Sodium Vinyl Sulphonate may also be grafted to polymeric supports (e.g. polystyrene) to give highly acidic ion exchangers, which used as catalysts for esterification and Friedel-Crafts acylations.[10] Where the sulfonic acid functionality is not essential, the much more usable alkaline aqueous solution of sodium vinylsulfonate is used, which is obtained directly in the alkaline hydrolysis of the carbyl sulfate and is commercially supplied as an aqueous solution.
Sodium Vinyl Sulphonate is a useful reagent (monomer) for the formation of poly(anionic) polymers and copolymers. Sodium Vinyl Sulphonate is employed as a basic brightener and leveling agent in nickel baths. Sodium Vinyl Sulphonate is also used as intermediate for organic synthesis, surfactant, pharmaceutical industry. Store in cool place. Keep container tightly closed in a dry and well-ventilated place. Sodium Vinyl Sulphonate is sensitive to light. Incompatible with oxidizing agents. The subject invention provides: a method for producing vinyl sulfonic acid, comprising conducting demetallation of vinyl sulfonate salt, wherein the demetallation rate is not less than 95% according to the following formula: Demetallation rate(%)={(acid value after demetallation)/(acid value before demetallation)}×100;
a method for producing vinyl sulfonic acid, comprising conducting demetallation of vinyl sulfonate salt, wherein demetallation is carried out using a strongly acidic ion exchange resin; and said method further comprising the step of purifying a product of the demetallation using a thin film evaporator. Vinylsulfonic acid (PVS) possesses a high acid content (ion‐exchange capacity in the chemical formula = 9.2 meq · g-1). Its monomer, vinylsulfonic acid (VSA), had a high acid dissociation ability (Hammett acid function = 0.74 in water), and a high ionic conductivity (0.04-0.11 S · cm-1). The radical polymerization of Sodium Vinyl Sulphonate with various initiators was kinetically investigated. The ESR spectrum of the Sodium Vinyl Sulphonate polymerization mixture showed a strong signal ascribed to the propagation carbon radical of Sodium Vinyl Sulphonate. The molecular weight of PVS increased with the increasing monomer concentration and decreasing radical initiator concentration to yield the PVS with a molecular weight of 4.0 × 104. Proton‐conductivity of PVS under hydrated and nonhumidified conditions was on the order of 10-1 and 10-3-10-6 S · cm-1, respectively.
Sodium Vinyl Sulphonate is the organosulfur compound with the formula CH2=CHSO3H. Sodium Vinyl Sulphonate is the simplest unsaturated sulfonic acid. The C=C double bond is a site of high reactivity. polymerize gives polyvinylsulfonic acid, especially when used as a comonomer with functionalized vinyl and (meth)acrylic acid compounds. Sodium Vinyl Sulphonate is a colorless, water-soluble liquid, although commercial samples can appear yellow or even red. Sodium Vinyl Sulphonate is produced industrially by the alkaline hydrolysis of carbyl sulfate with subsequent acidification of the resulting Sodium Vinyl Sulphonate The activated C=C double bond of Sodium Vinyl Sulphonate reacts readily with nucleophiles in an addition reaction. 2-Aminoethanesulfonic acid is formed with ammonia and 2-methylaminoethanesulfonic acid with methylamine.
Sodium Vinyl Sulphonate is the monomer in the preparation of highly acidic or anionic homopolymers and copolymers. These polymers are used in the electronic industry as photoresists, as ion-conductive polymer electrolyte membranes (PEM) for fuel cells. For example, transparent membranes with high ion exchange capacity and proton conductivity can be produced from polyvinylsulfonic acid.Sodium Vinyl Sulphonate may also be grafted to polymeric supports (e.g. polystyrene) to give highly acidic ion exchangers, which used as catalysts for esterification and Friedel-Crafts acylations. Where the sulfonic acid functionality is not essential, the much more usable alkaline aqueous solution of sodium vinylsulfonate is used, which is obtained directly in the alkaline hydrolysis of the carbyl sulfate and is commercially supplied as an aqueous solution..
Low Color StabilizerSodium Vinyl Sulphonate Contains Sulphonate Group that Polymerize, Also Modify Olefinic Bond And Boost End Solubility Of The End Product. Water-Based Adhesive, Water-Based Paint Resin And Nickel Shine Producer Sodium Vinyl Sulphonate is a polymerizable organic compound which has many industrial uses, particularly as an antistatic agent and as an agent improving the tinctorial affinity of synthetic fibres, such as polyacrylonitrile and polypropylene, to cationic dyes, as a dispersing agent in polymer emulsions, as a wetting agent for lowering the mixing water content of cement, as a starting material for the production of cation exchange resins and synthetic rubber.Sodium Vinyl Sulphonate and its derivatives can be prepared from ß-chloroethanesulfonyl chloride or carbyl sulfate (ß-hydroxysulfonyloxyethanesulfonic anhydride). The chemistry of Sodium Vinyl Sulphonate has assumed industrial importance since the discovery of a simple synthesis of ß-chloroethanesulfonyl chloride from chloroethane or ethane, sulfur dioxide, and chlorine by the Reed process. Carbyl sulfate is as important a starting material as ß-chloroethanesulfonyl chloride, and surpasses the latter in some respects, e.g. on account of the low price of its components ethylene and sulfur trioxide. Vinylsulfonates undergo addition reactions with alcohols, phenols, thiols, sulfinic acids, carboxylic acids, amides, imides, and hydrazides, as well as with amines, ureas, diazonium salts, and nitroparaffins. Furthermore, they undergo halogenation, nitration, olefination, and the Diels-Adler reaction. - Methods for the preparation of the free Sodium Vinyl Sulphonate are described. Alkyl vinylsulfonates are excellent alkylating agents. The derivatives of Sodium Vinyl Sulphonate are used e.g. as plasticizers, emulsifiers, and fungicides.More easily handled than the acid is the salt, sodium vinylsulfonate, which is commercially supplied as an aqueous solution.
IUPAC NAME :
sodium ethenesulfonate;sodium ethylenesulfonate;sodium ethylenesulphonate;
Provichem 2202 ,sodium vinyl sulphonate;sodium ethylenesulphonate;Reaction mass of disodium 2,2’-;oxydiethanesulfonate and sodium;ethenesulfonate;trisodium 2-(2-sulfoethoxy)ethane-1-;sulfonate ethenesulfonate
TRADE NAME :
Properties of Vinylsulfonic acid;Chemical formula of Vinylsulfonic acid;
C2H4O3S;Molar mass of Vinylsulfonic acid 108.11 g·mol-1;Appearance of Vinylsulfonic acid colouless liquid
OTHER NAME :
3039-83-6;25053-27-4;9002-97-5;SC-25619;DB-047774;9461405D9F;FT-0625733;FT-0700547
Sodium Vinyl Sulphonate is a useful reagent (monomer) for the formation of poly(anionic) polymers and copolymers.Sodium ethylenesulphonate(3039-83-6) is widely used in the synthesis of auxiliary materials for environment friendly water treatment emulsifier, pure acrylic emulsion, styrene-acrylic, acetic styrene-acrylic emulsion and other emulsions. Sodium Vinyl Sulphonate used in synthetic fibre and polymeric invert monomer for its many good characteristics, such as stability, resistibility and reducing shrinkage cavity. Sodium ethylenesulphonate(3039-83-6) also used as sulfo-group ethyl auxiliaries, electrofacing gloss agent, surfactant, pharmaceutical intermediates and other fields. Sodium Vinyl Sulphonate application areas are Wetting Agents, Coatings, Dyes, Fibers, Polymers, Resins. Sodium Vinyl Sulphonate also can be prepared by dehydration of isethionic acid with phosphorus pentoxide
Sodium Vinyl Sulphonate can also be prepared by sulfochlorination of chloroethane, dehydrohalogenation to vinylsulfonyl chloride and subsequent hydrolysis of the acid chloride. The activated C=C double bond of Sodium Vinyl Sulphonate reacts readily with nucleophiles in an addition reaction. 2-Aminoethanesulfonic acid is formed with ammonia and 2-methylaminoethanesulfonic acid with methylamine.
Sodium Vinyl Sulphonate is the monomer in the preparation of highly acidic or anionic homopolymers and copolymers. These polymers are used in the electronic industry as photoresists, as ion-conductive polymer electrolyte membranes (PEM) for fuel cells. For example, transparent membranes with high ion exchange capacity and proton conductivity can be produced from polyvinylsulfonic acid. Sodium Vinyl Sulphonate may also be grafted to polymeric supports (e.g. polystyrene) to give highly acidic ion exchangers, which used as catalysts for esterification and Friedel-Crafts acylations.[10] Where the sulfonic acid functionality is not essential, the much more usable alkaline aqueous solution of sodium vinylsulfonate is used, which is obtained directly in the alkaline hydrolysis of the carbyl sulfate and is commercially supplied as an aqueous solution.
Store in cool place. Keep container tightly closed in a dry and well-ventilated place. Sodium Vinyl Sulphonate is sensitive to light. Incompatible with oxidizing agents. The subject invention provides: a method for producing vinyl sulfonic acid, comprising conducting demetallation of vinyl sulfonate salt, wherein the demetallation rate is not less than 95% according to the following formula:
Demetallation rate(%)={(acid value after demetallation)/(acid value before demetallation)}×100;
a method for producing vinyl sulfonic acid, comprising conducting demetallation of vinyl sulfonate salt, wherein demetallation is carried out using a strongly acidic ion exchange resin; and said method further comprising the step of purifying a product of the demetallation using a thin film evaporator. Sodium Vinyl Sulphonate possesses a high acid content (ion‐exchange capacity in the chemical formula = 9.2 meq · g-1). Its monomer,Sodium Vinyl Sulphonate, had a high acid dissociation ability (Hammett acid function = 0.74 in water), and a high ionic conductivity (0.04-0.11 S · cm-1). The radical polymerization of Sodium Vinyl Sulphonate with various initiators was kinetically investigated. The ESR spectrum of the Sodium Vinyl Sulphonate polymerization mixture showed a strong signal ascribed to the propagation carbon radical of Sodium Vinyl Sulphonate.
The present paper reports the graft copolymerization of vinyl sulfonic acid onto sodium carboxymethyl cellulose by free radical polymerization using potassium peroxydiphosphate/thiourea redox system in an inert atmosphere. The reaction conditions for maximum grafting have been optimized by varying the concentration of vinyl sulfonic acid (2.6 × 10−2–8.0 × 10−2 mol dm−3), potassium peroxydiphosphate (4.0 × 10−2–20 × 10−2 mol dm−3), thiourea (0.8 × 10−3–4.0 × 10−3 mol dm−3), sulphuric acid (1.0 × 10−3–6 × 10−3 mol dm−3), sodium carboxymethyl cellulose (0.6–1.6 g dm−3) along with time duration (60–180 min) and temperature (30–50 °C). Water swelling capacity, metal ion sorption, flocculation studies and resistance to biodegradability of synthesized graft copolymer have been performed with respect to the parent polymer. The graft copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis.
Sodium Vinyl Sulphonate and its derivatives can be prepared from β‐chloroethanesulfonyl chloride or carbyl sulfate (β‐hydroxysulfonyloxyethanesulfonic anhydride). The chemistry of Sodium Vinyl Sulphonate has assumed industrial importance since the discovery of a simple synthesis of β‐chloroethanesulfonyl chloride from chloroethane or ethane, sulfur dioxide, and chlorine by the Reed process. Carbyl sulfate is as important a starting material as β‐chloroethanesulfonyl chloride, and surpasses the latter in some respects, e.g. on account of the low price of its components ethylene and sulfur trioxide. Vinylsulfonates undergo addition reactions with alcohols, phenols, thiols, sulfinic acids, carboxylic acids, amides, imides, and hydrazides, as well as with amines, ureas, diazonium salts, and nitroparaffins. Furthermore, they undergo halogenation, nitration, olefination, and the Diels‐Adler reaction. – Methods for the preparation of the free Sodium Vinyl Sulphonate are described. Alkyl vinylsulfonates are excellent alkylating agents. The derivatives ofSodium Vinyl Sulphonate are used e.g. as plasticizers, emulsifiers, and fungicides.
This study aims to evaluate the effects of etching with sulfuric acid (SA) and vinyl sulfonic acid (VSA) on the bond strength between a light-curing indirect resin composite and polyetherketoneketones (PEKK). PEKK specimens were ground with 600 silicon carbide papers, etched with 90% SA for 5 s (90-5 SA) or 95% VSA for 30 s (95-30 VSA), and then modified with a phosphate primer; afterward, a light-curing resin composite was veneered on the specimens. Two control groups were also prepared without etching (unetched/unprimed and unetched/primed). After 20,000 thermocycles in water at 4 and 60 °C, the shear bond strengths of the specimens were determined and subjected to a nonparametric (Steel–Dwass) test (α = 0.05, n = 8). The etched surfaces were observed by scanning electron microscopy (SEM) at 2000× magnification.
Higher bond strengths were obtained when the PEKK surface was etched with 90-5 SA or 95-30 VSA (90-5 SA/unprimed 24.3 ± 4.3 MPa, 90-5 SA/primed 26.2 ± 3.2 MPa, 95-30 VSA/unprimed 23.7 ± 2.5 MPa, 95-30 VSA/primed 24.3 ± 4.1 MPa), and these values were not statistically different, whereas the two control groups exhibited significantly lower bond strengths (unetched/unprimed 12.2 ± 1.7 MPa, unetched/primed 9.5 ± 2.7 MPa). SEM observations revealed that 95-30 VSA led to a microporous (felt-like) surface, which was different from the surface structure etched with 90-5 SA. Etching the PEKK surface with SA or VSA significantly improved the bond strength between resin composite and PEKK in contrast with the application of the phosphate primer. Appropriate chemical etching could be a useful option when fabricating prostheses using PEKK-based materials and indirect resin composites.
This work studied the effects produced on the ultrafiltration membrane during metal ion recovery by polymer-enhanced ultrafiltration (PEUF) using poly(vinyl sulfonic acid) (PVSA), as water-soluble polymer by means of enrichment method and at different pHs. The fouling was described (by permeability measurements, application of series resistance model, ATR-FTIR spectrum and AFM images) and membrane–metal ion interaction was studied (by calculating of interaction coefficient from metal ion concentration in the permeated as function of permeated volume). The resistance was observed to increase with decreases in pH (from 2.0 × 1012 at pH 6.0 to 10.7 × 1012 m−1 at pH 3.0; from 11.5 × 1012 at pH 6.0 to 19 × 1012 m−1 at pH 3.0 for clean and fouled membrane, respectively). The fouling layer thickness was found to be greater at more acid pHs, where Sodium Vinyl Sulphonate was similar at pH 3.0 (0.19 μm) and 4.5 (0.23 μm) in comparison with the thickness at pH 6.0 (0.08 μm). The increase in membrane–metal ion interaction was used to define a sequence of affinity between metal ion and the fouling layer formed (Ni2+ < Cu2+ < Co2+ < Zn2+ < Cd2+), although Pb2+ presented atypical behavior for all the pHs studied. Membrane–metal interaction coefficient (R0) was found to be associated to a good degree with a decrease of the respective hydrated ionic radius, indicating that the electrostatic nature is not the main interaction in the adsorption of metal ions on the clean and fouled membrane during PEUF when using PVSA.
P(AAM-co-VSA) hydrogel was prepared at different mole ratios form the corresponding monomers and used in absorption of metal ions such as Co and Ni from aqueous environments. Then, these bound metal ions within the hydrogel matrices were reduced to their metal nanoparticles by aqueous NaBH4 treatment. Finally, p(AAm-co-VSA)–M (M: Co or Ni) composites were used as reactor in the hydrolysis of NaBH4 for hydrogen generation. The amounts of metal ions before and after metal nanoparticle formation were determined by Atomic Absorption Spectroscopy (AAS). P(AAm-VSA) hydrogel showed greater absorption tendency for Ni(II) ions than Co(II) ions, and the metal ion binding capacity of these hydrogels was increased with an increase in the amount of VSA in the copolymeric hydrogel. Sodium Vinyl Sulphonate was also found that although the amount of Ni ions loaded into the hydrogel matrices were more than Co ions, Co metal nanoparticle-containing hydrogel produced hydrogen faster than Ni metal nanoparticle-containing hydrogel composites. The activation energy for the Co nanoparticle-embedded p(AAm-co-VSA) was found as 34.505 kJ mol−1k−1, and other thermodynamic parameters were also calculated. The p(AAm-co-VSA)–Co hydrogel can be used up to 5 times repetitively without any loss of yield but with 55% of catalytic activity.
A novel multi-component superabsorbent polymer, poly(methacrylic acid-co-vinyl sulfonic acid)-grafted-magnetite/nanocellulose composite (P(MAA-co-VSA)-g-MNCC) was prepared by graft copolymerization technique. The characteristics of the P(MAA-co-VSA)-g-MNCC were investigated using XRD, FTIR, ESR and TG analyses. The swelling of P(MAA-co-VSA)-g-MNCC was found to be increased with increase of time and pH. The antibody, Immunoglobulin (IgG) was adsorbed onto P(MAA-co-VSA)-g-MNCC, under different optimized conditions. An adsorbent dose of 3.0 g/L was sufficient for the complete recovery of IgG from aqueous solutions. The maximum IgG adsorption on the ion-exchange adsorbent was observed at pH 6.8 with an equilibrium time of 3.0 h. Pseudo-second-order kinetic model adequately described the kinetic rate in comparison to pseudo-first-order model. The experimental adsorption isotherms of IgG were well fitted by Sips model and maximum adsorption capacity based on Langmuir model was 200.21 mg/g at 30 °C. IgG adsorption was highly dependent on ionic strength. Studies on the separation of IgG from mixture of proteins were carried out to ensure its better applicability in the biotechnological and biomedical fields. Regeneration of the spent adsorbent was done with 0.01 M KOH without significant loss in adsorption capacity.
Hydrogels are one of the potential polymeric materials that do not dissolve in water at physiological temperature or pH but swell considerably in aqueous media. These are cross-linked polymeric materials in a three-dimensional network which can absorb and retain significant amount of water, making them suitable material for wide range of applications in bioengineering, biomedical, food, and pharmaceutical industries. The water insoluble behavior is attributed to the presence of chemical or physical cross-links which provide the integrity and physical stability to the system. The porous nature of hydrogels facilitates the permeation of water through network structure which is highly influenced by several factors such as chemical composition, hydrophilicity as well as chemical structure of polymer, cross-link densities, and also the functionality of cross-linkers.
Stimuli-responsive hydrogels have gained a significant attention and are being developed as drug carrier systems for site specific drug delivery as these hydrogels show dramatic changes in their volume and properties in response to external stimuli such as temperature, ionic strength, and pH. The optimum use of hydrogel depends upon the properties, namely, equilibrium swelling, swelling kinetics, network permeability, and biocompatibility which can be controlled by adjusting the ratios of monomer to cross-linkers or polymers. Cross-linking is one of the most important factors that affect swelling of the hydrogels. The structure and elasticity of hydrogel are highly dependent on the nature of cross-linking agent as well as on the average molecular mass between the cross-links. The network structure parameters are critical in describing the mechanical strength, porosity, and releasing mechanics of encapsulated drugs. Previously, pH-sensitive poly(acrylamide-co-itaconic acid) hydrogels were synthesized, and influence of network parameters on the swelling and mechanical strength was analyzed. The results clearly demonstrate that network parameters are the key factors in controlling the behavioural changes in the properties of hydrogels.
Natural and synthetic materials have been used extensively for the synthesis of hydrogels. Acrylic acid (AA) is deemed to form a super absorbent polymer which can absorb very large amount of water and retain Sodium Vinyl Sulphonate even under high pressure. As a result of this unique characteristic, Sodium Vinyl Sulphonate has been used in various controlled drug delivery systems. The swelling behaviour of poly(AA) hydrogels is highly dependent on the pH of the surrounding medium due to the presence of carboxylic groups. Polyvinylsulfonic acid (PVSA; as sodium salt), which is a polyelectrolyte that has negatively charged sulfonate groups, is a blood compatible polymeric material. Due to negatively charged character of sulfonate groups, this polymer may be used as coating material.
Here we report AA/PVSA based hydrogels for controlled delivery of a model drug, namely, isosorbide mononitrate. Isosorbide mononitrate is an organic nitrate used in prophylaxis of angina pectoris, acute myocardial infarction, and heart failure. In this respect, a series of hydrogels of AA and PVSA chemically cross-linked using ethylene glycol dimethacrylate (EGDMA) were synthesized via free radical polymerization technique. The prepared hydrogels were subjected to dynamic and equilibrium swelling studies while the drug release was studied in various physiological mimic solutions. Influence of structural parameters on the prepared hydrogels was studied. Any drug-to-polymer interactions were studied using Fourier-transformation infrared spectroscopy (FTIR) while thermal effects were analysed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).
Isosorbide mononitrate was a gift sample from Hamaz Pharmaceuticals Ltd., Multan, Pakistan. Acrylic acid and vinylsulfonic acid as its sodium salt were sourced from Sigma-Aldrich, UK, and used without further purification. Ethanol, ethylene glycol dimethacrylate (EGDMA), and benzyl peroxide (BPO) were purchased from Merck, Germany, and used as received with a minimum purity of 99%. Double-distilled water was used throughout the experiments. A series of AA/VSA hydrogels were synthesized after the modification of procedure reported earlier. Composition of prepared hydrogels is summarized in Table 1 which were based on the previous experiments. Essentially, weighed amount of VSA (as sodium salt) was dissolved in water in a 50 mL round bottom flask at ambient temperature under constant stirring. Varying amounts of EGDMA and BPO were dissolved in AA in a separate flask. Both mixtures were then mixed thoroughly under continuous stirring until homogenized and the final weight up to 100 g was achieved with double-distilled water. This solution was poured into glass tubes having 16 mm internal diameter and 150 mm length. Each test tube was purged with nitrogen gas for 10–20 minutes to remove air bubbles.
These tubes were capped and then placed in water bath maintained at a temperature of 50°C for 48 h. After this period, tubes were taken out and cooled to room temperature. The hydrogels obtained were cut into discs of 6 mm length and immersed into 50 : 50 v/v ethanol-water solution for complete removal of catalyst and unreacted monomers. Gel discs were thoroughly washed until the pH of solution was same as the solution before washing. The hydrogels obtained were dried at 40°C until a constant weight was achieved and then were stored in vacuum desiccators for further use. The dynamic swelling ratio was evaluated gravimetrically in 100 mL 0.05 M USP phosphate buffer solutions of various pHs, that is, 1.2, 5.5, 6.5, and 7.5. Preweighed dried hydrogels discs were immersed in solutions of desired pH at a temperature of 37°C. Swollen gels were removed from the medium at a predetermined interval of time for 8 hours, weighed after blotting them dry with filter paper, and placed in the same bath. The swelling ratio was calculated from the following.
The average molar mass of the chains between cross-links , directly related to the cross-link density, is an important parameter in characterizing the structural parameters of hydrogels. Physical and mechanical properties of cross-linked hydrogels are significantly influenced by the . According to Flory-Rehners theory, can be calculated using where is the volume fraction of the swollen hydrogel at equilibrium, is the molar volume of the solvent (mL mol−1), is Flory-Huggin’s solvent interaction parameter between solvent and polymer, and is the density of gel (g mL−1). Dried discs of hydrogel samples were powdered in pestle and mortar. The powdered material was mixed with potassium bromide (Merck IR spectroscopy grade) in 1 : 100 proportion and dried at 40°C. The mixture was compressed to semitransparent disc of 12 mm diameter by applying a pressure of 65 kN (pressure gauge, Shimadzu) for 2 minutes. The FTIR spectrum over the wave length range 4000–400 cm−1 was recorded using FTIR spectrometer (FTIR 8400 S, Shimadzu).
Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to characterize hydrogel for thermal stability. DSC was done in the DSC unit (Netzsch DSC-200 PC Phox, Germany). The samples were heated in a close aluminum pan at the rate of 40°C/min under nitrogen flow (50 mL min−1). TGA was performed using a thermogravimetric analyzer (TGA 951, TA Instruments, USA). Samples were heated at the rate of 10°C/min with temperature range of 30–400°C. Dried hydrogel discs were immersed in 10 mL of isosorbide mononitrate solution (1% w/v) prepared in ethanol-water mixture (50 : 50% v/v). These hydrogels were kept at ambient temperature without stirring for 7 days to attain equilibrium swelling. After reaching equilibrium swelling point, discs were removed from the loading solution, blotted with filter paper, and dried in an oven at 45°C for 7 days. The amounts of drug loaded were calculated by recurrently extracting the drug from the hydrogels in ethanol-water mixture (50 : 50% v/v) and the concentration of drug in pooled extract was monitored spectrophotometrically at 210 nm. The experiments were conducted in triplicate.
Drug release studies were carried out in USP II dissolution apparatus (Pharma Test, Germany) using 0.05 M USP phosphate buffer solutions at various physiological pHs (1.2, 6.5, and 7.5). The weighed hydrogel discs were immersed in 500 mL dissolution medium stirred at a rate of 100 rpm, and maintained at 50°C. With each sampling, 5 mL release media was withdrawn at predetermined time and immediately replenished with the same volume of fresh medium to maintain sink conditions. The determination of isosorbide mononitrate release was carried out at 210 nm for up to 12 h at regular intervals. Drug release data were fitted to various kinetic models including zero-order, first-order, Higuchi, and Korsmeyer-Peppas models. These models are generally used when more than one type of release phenomena is involved.
The poly(acrylic-co-vinylsulfonic) acid hydrogels were synthesized using AA as the monomer, PVSA as the polymer, and EGDMA as the cross-linker in the presence of BPO as an initiator of free radical polymerization. Schematic depiction of the synthesis of cross-linked hydrogel is shown in Figure 1. Since AA and VSA are negatively charged polyelectrolytes in the polymerization medium; therefore, strong electrostatic repulsive forces would operate between AA and VSA groups. Sodium Vinyl Sulphonate is envisaged that a possible expanded network of poly(AA/VSA) hydrogel would be obtained that has a higher swelling capacity.