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This article described the synthesis and characterization of new copolymer hydrogels containing two hydrophilic units-methacrylic acid (MAA) and 2-Acrylamido-2-methylpropane sulfonic acid (AMPS). The resulting hydrogels were characterized by various techniques: FTIR, Elemental analysis, SEM, Dynamic Molecular simulation, Dynamic-Mechanical analysis and DSC in order to confirm the structure of hydrogels and to predict the best ratio composition with enhanced physical chemical properties. The swelling behavior in water was studied as a function of ratio of monomers and their concentration in medium. An increase in AMPS content led to expansion of network and increase in swelling degree capacity in water. An increase in AMPS content did not significantly influence the glass transition temperature of copolymers, indicated that the physical properties of initial components were preserved. The equal amount of monomers contributed to the highest strength of hydrogels. Meanwhile, the introduction of AMPS to the system was an effective method for improving the performances of the poly(methacrylic acid)- based hydrogels. (C) 2016 Elsevier B.V. All rights reserved.

Manufacturing of synthetic composites consumes huge energy and their disposal at the end of the life cycle is very difficult since there is virtually no recycling option. Therefore, biocomposite materials have recently received considerable attention in academic research and industrial application compared to the synthetic composite materials due biodegradability, nontoxicity and economical point of view. Biocomposite membranes of highly methylated pectin and SBA-15, a form of mesoporous silica, were prepared by membrane casting. The amount of SBA-15 was 10%, 20% and 30% by membrane mass. These membranes were characterized by optical microscopy, FTIR, XRD, thermogravimetry, mechanical analysis and swelling in water, HCl, NaOH and methanol. The incorporation of SBA-15 in pectin matrix enhanced the stability of these membranes in all tested solutions, compared to the pure pectin membranes. The pectin/SBA photomicrographs contain rod-like domains which indicate the presence of SBA-15 in membrane. Mechanical analysis proves that incorporation of SBA-15 enhances the elasticity and tensile strength of pectin membranes. Thermogravimety in nitrogen has shown that the presence of SBA-15 in the membranes increased the onset temperatures of pectin degradation. The novel composite material represents promising way for practical membrane application. (C) 2014 Elsevier Ltd. All rights reserved.

Pectin, with its tendency to gel in the presence of metal ions has become a widely used material for capturing the metal ions from wastewaters. Its dye-capturing properties have been much less investigated, and this paper is the first to show how films based on amidated pectin can be used for cationic dye adsorption. In the present study amidated pectin/montmorillonite composite films were synthesized by membrane casting, and they are stable in aqueous solution both below and above pectin pK(a). FTIR, thermogravimetry and SEM-EDAX have confirmed the presence of montmorillonite in the cast films and the interactions between the two constituents. In order to evaluate the cationic dye adsorption of these films Basic Yellow 28 was used, showing that the films have higher adsorption capacity compared to the others reported in the literature. The results were fitted into Langmuir, Freundlich and Temkin isotherms indicating an exothermic process and setting the optimum amount of montmorillonite in the films to 30% of pectin mass. According to the Langmuir isotherm the maximum adsorption capacity is 571.4 mg/g. (C) 2013 Elsevier B.V. All rights reserved.

Films of chitosan and poly(itaconic acid) in various different ratios have been prepared by membrane casting. The enhancement in the proton conductivity and uptake of water was observed as the content of poly(itaconic acid) in film increased. The proton conductivity of chitosan/poly(itaconic) films was comparative with commercially used synthetic sensor Nafion 117. Films showed thermal stability up to 185 degrees C. The proposed experiment might open up a new possibility for use of chitosan/poly(itaconic acid) films as a biosensors due to their advantages: low cost, simple preparation and good conductive sensitivity. (C) 2015 Elsevier B.V. All rights reserved.

Composites based on poly(methacrylic acid) (PMAA) and two types of zeolite, hydrophilic zeolite A and hydrophobic zeolite ZSM-5, were synthesized. The obtained hydrogel composites that combine well the strong interaction between PMAA and cationic species, the accessibility of active sites in the swollen network and fine mechanical stability of zeolites are considered promising candidates for removal of cationic dye, basic yellow 28 (BY28) from aqueous solutions. The adsorption was found to be highly dependent on composition of hydrogel composites, initial dye concentration, solution pH, sorbent mass and temperature, while the effect of zeolite type is less manifested. It was found that the surface adsorption influenced the kinetics of adsorption which was determined by the rate of movement of the boundary layer of BY28 adsorbed on hydrogel surface. Adsorption processes were found to be favorable and preferably physical in nature with maximum adsorption capacity that could reach up to 180 mg/g for PMAA/30A hydrogel composite. Image analysis was applied on differently colored hydrogels and revealed the linear correlation between equilibrium adsorption capacities and the mean values of pixel intensity, as well as the strong effect of initial dye concentration on uniformity of coloration along the hydrogel diameter.

Poly(methacrylic acid) based hydrogels with neutralization degree of monomer of 0% (PMAA/0) and 80% (PMAA/80) were synthesized and their sorption potentials toward model cationic dye, basic yellow 28 (BY28), from aqueous solution, were investigated. FTIR and SEM analysis were conducted to confirm the structure and morphology of the sorbents. Investigation of the effect of the initial dye concentration, the solution pH, the sorbent mass and the temperature on sorption process, as well as the sorption kinetics and equilibrium studies were performed by batch technique. Sorption capacities of both sorbents showed to be highly sensitive to external conditions change, especially those affecting hydrogel swelling degree. Kinetic studies showed that the pseudo-first order kinetic model well fitted the experimental data and that sorption of BY28 onto PMAA hydrogels could be very well described with phase-boundary controlled models. Thermodynamical data revealed spontaneous endothermic processes. In case of PMAA/0 hydrogel physisorption was dominant, while in case of PMAA/80 hydrogel, both, the physisorption and chemisorption were presented. Langmuir, Freundlich and Dubinin–Radushkevich sorption isotherms were applied on equilibrium sorption data. The saturated sorption amount could reach up to 102 mg g −1 and 157 mg g −1 for PMAA/0 and PMAA/80 hydrogel, respectively. Image analysis proved to be useful method for analysis of uniformity of coloration along the hydrogel diameter. Both hydrogels displayed good properties in cationic dye removal, but higher sorption capacities, percentage of removed dye and significant acceleration of sorption of BY28 were accomplished by neutralizing the monomer up to 80%.

Poly(methacrylic acid) hydrogels were synthesized. The effects of the synthesis parameters: the neutralization degree of methacrylic acid and the concentrations of monomer, crosslinker and initiator on the xerogels structural properties: the xerogel density ( ρ xg ), the number average molar mass between the network crosslinks ( M c ), the crosslink degree ( ρ c ), the number of elastically effective chains totally induced in a perfect network per unit volume ( V e ), the distance between the macromolecular chains ( ξ ) and the equilibrium swelling degree ( SD eq ) and the swelling kinetics was investigated. As the concentrations of crosslinker, monomer and initiator increase, the value of ρ xg , ρ c and V e increases and decreases the value of M c , ξ and SD eq . With the increase in the neutralization degree of methacrylic acid, the values of ρ xg , M c , ξ , SD eq increase, while the ρ c and V e decrease. The xerogels structural properties, SD eq and swelling kinetic parameters are mainly in power law form functional relationships with the synthesis parameters as well as with the xerogels crosslinking degree.

The diffusion of water into solid poly(ditetrahydrofurfuryl itaconate) (PDTFI) films and in analogous polymer solutions was measured. Diffusion into solid PDTFI films on a glass support was measured in three solutions of different pH (4, 7 and 10) at 37 and 60 degrees C during a 90 day period. The uptake was high and was both pH and. temperature dependent, ranging from 120 to 2000%. A Fickian mechanism is observed for the initial stages of uptake, whilst a non-Fickian mechanism is present when the equilibrium is approached. The pH 7 samples did not equilibrate at any temperature during the experiment. The FTIR investigations of the films indicated some deesterification took place during the uptake. The diffusion coefficients and diffusion exponents are calculated for the samples. The diffusion of water into PDTFI solution in acetone was measured by PGSE-NMR, showing the expected linear attenuation functions. The diffusion coefficient of water was calculated for polymer concentrations up to 10%.