In-situ stabilization of silver nanoparticles in polymer hydrogels for enhanced catalytic reduction of macro and micro pollutants

The in-situ stabilization of Ag nanoparticles is carried out by the use of reducing agent and synthesized three different types of hydrogen (anionic, cationic, and neutral) template. The morphology, constitution and thermal stability of the synthesized pure and Ag-entrapped hybrid hydrogels were efficiently confirmed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). The prepared hybrid hydrogels were used in the decolorization of methylene blue (MB) and azo dyes congo red (CR), methyl Orange (MO), and reduction of 4-nitrophenol (4-NP) and nitrobenzene (NB) by an electron donor NaBH4. The kinetics of the reduction reaction was also assessed to determine the activation parameters. The hybrid hydrogen catalysts were recovered by filtration and used continuously up to six times with 98% conversion of pollutants without substantial loss in catalytic activity. It was observed that these types of hydrogel systems can be used for the conversion of pollutants from waste water into useful products.

Synthesis of copolymeric hydrogels of acrylamide and 2-(hydroxyethyl methacrylate) and its use for the adsorption of basic blue 3 dye

Homo and copolymer hydrogels of acrylamide and 2-hydroxyethyl methacrylate (HEMA) were synthesized by free radical addition polymerization. The synthesized hydrogels were characterized by scanning electron microscopy (SEM), thermal gravimetric and differential thermal analysis (TGA/DTA). The hydrogels were used as an adsorbent for the removal of toxic azo dye Basic blue 3 (BB3) in aqueous medium. To check the swelling property the equilibrium swelling of these synthesized hydrogels were established within 24 h. The effect of pH, time and temperature in the process of BB3 adsorption was studied in detail. The maximum adsorption of BB3 on hydrogels was occurred at pH 9 with 60 min equilibration time. The kinetic data were applied to pseudo first order, pseudo second order and intraparticle diffusion model. The obtained results indicate that the adsorption process, obey pseudo second order kinetics and is diffusion control. The negative value of ΔS and positive values of ΔG and ΔH showed that the adsorption process is orderliness, non-spontaneous and endothermic respectively in nature. The hydrogels were successfully regenerated from the mixture and used again in several steps without a reduction in their efficiency.

Synthesis and Rheological Survey of Xanthan Gum Based Terpolymeric Hydrogels

Graft copolymerization technique was used to synthesize novel biopolymer based terpolymeric hydrogels of xanthan gum (Gx), acrylic acid and N-Isopropyl acrylamide (NIPAM) by using chemical crosslinker N,N′-methylene bisacrylamide (MBA), ammonium persulphate (APS) as a redox initiator and sodium dodecyl sulphate (SDS) for particle size stabilization. The synthesized hydrogels were characterized through FT-IR and SEM techniques, which confirmed the hydrogels formation. Detailed rheology was investigated through applying various rheological models like Bingham model, modified Bingham model and Ostwald power law model to the hydrogels which revealed that the hydrogels were appeared to have shear thinning, non-Newtonian behavior and more elastic. Modified Bingham model provided best fit understanding to our prepared materials. The maximum activation energy (Ea) 13.87 kJ/mol was obtained for composition having more Gx compared to others, showing a strong relationship with viscosity. The hydrogels has potential to find applications in food industry, cosmetics, degradation of dyes and removal of heavy metals from waste water.

Rheological Investigation of GO Doped p(APTMACl) Composite Hydrogel

The aim of the present work is an approach towards the exploration of comprehension of rheological work on polymer composites synthesized by ex-situ dispersion of graphene oxide (GO) in poly(3-acrylamidopropyl trimethyl ammonium chloride (APTMACl) cationic hydrogel template. FTIR was carried out for confirmation of polymer synthesis and existence of GO in hydrogel network. The rheological investigation via frequency sweep curve (shear measurement) and oscillatory sweep (dynamic mechanical analysis) at different temperature 20, 25, 30, 35, 40 and 45 °C was performed. The storage (G′) and loss (G′′) moduli as a function of angular frequency, yield stress, tangent loss, damping factor and retention property were also studied to confirm the visco-elastomeric nature of the GO@p(APTMACl) composite and their semi solid response at different range of temperature. Various rheological models like Bingham model, modified Bingham model and Ostwald’s power law were applied. The temperature dependency was further tested via Arrhenius-Frenkel-Eyring equation. The sample showed best fitting in the modified Bingham model, which justified the pseudo plastic semi solid behavior of GO@p(APTMACl) composite within the linear visco-elastic region (LVER). All the properties from rheological study show best mechanical property and make the composite hydrogel good for drug delivery and for other environmental applications.

Preparation and Physicochemical Characterization of Dual Responsive and Chemically Modified Cellulose Based Copolymer Hydrogels

This research work is based on the preparation and physicochemical characterization of Poly(N-isopropylacrylamide)–Cellulose–Poly(Acrylic acid) [PNIPAAm–Cellulose–PAAc] based terpolymer hydrogels. The free radical polymerization reaction was initiated by the presence of ammonium persulphate (APS) and crosslinking between different monomers was occurring through N,Nl- Methylene bis-acrylamide (MBA). Confirmation of polymerization process was done by FT-IR and UV-visible spectroscopy. The prepared hydrogels were further characterized by different physicochemical techniques like rheology, Ostwald viscometry and dynamic light scattering (DLS). The effect of external stimuli like temperature, pH and composition of the samples on the physicochemical behavior was also carried out by dynamic rheology, swelling measurement and DLS. Various other properties like elasticity, shear stress, shear strain, loss modulus, storage modulus and complex viscosity was investigated by rheology. DLS was used to trace the size and swelling behavior of the samples. From the results obtained it was found that all the microgel samples are stimuli responsive and most of their physicochemical properties were prominently varying while changing the internal as well as the external experimental variable. These changes in physicochemical behavior of the gel can be attributed to two possibilities; the change in the hydrophobic character of gel (PNIPAAm) with temperature and also to the weakening of intermolecular hydrogen bonds with increase in temperature. As a result of this the PAA chains may undergo a transition from a compact conformation to an expanded coil conformation, resulting in the swelling of the hydrogels.

The Effect of Low Weight Percent Multiwalled Carbon Nanotubes on the Dielectric Properties of Non-Conducting Polymer/Ceramic Nanocomposites for Energy Storage Materials

Here in this study timing saving, easy and cost effective methods has been applied for fabricating the dielectric energy storage materials. Ceramic nanoparticles (FLZC’s) have been successfully synthesized by Sol-Gel method and its nanocomposites with non-conducting polymers (PVP, PVA, PEG, PEO) and multiwalled carbon nanotubes (MWCNT’s) by one-pot blending technique. Energy dispersive x-ray diffraction (EDX), x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA/DTA), AC impedance analyzer and dielectric properties were determined for all the samples. Dielectric properties showed good agreement with that of energy storage substances for electronic device fabrication. High dielectric constant was achieved when 0.5 wt% MWCNT’s was added to FLZC’s/MWCNT’s/Polymer nanocomposites. The stability and performance of the nanocomposites were dependent on the type of polymer used. These preparation materials can be employed in functional materials, such as high charge-storage capacitors, electrostriction for artificial muscles and smart skins etc.

Zwitterionic superabsorbent polymer hydrogels for efficient and selective removal of organic dyes

A novel zwitterionic superabsorbent polymer hydrogel [ZI-SAH] was synthesized by free radical polymerization and used for the removal of crystal violet (CV) and congo red (CR) from an aqueous medium.