Water Absorbency Of Hydrogels Research Articles

Jelatin/PAAm-tabanlı IPN Hidrojelleri Kullanarak Sulu Çözeltiden Krom (VI) Uzaklaştırmasının Değerlendirmesi

In this work, gelatin (G)-polyacrylamide (PAAm)-based interpenetrating polymer network (IPN) hydrogels involving maleic acid (MA) was prepared using by radical polymerization. Full-IPN and semi-IPN hydrogels were synthesized by using glutaraldehyde and ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The water absorbency of hydrogels was investigated, and the values increased with MA and G. The chemical structures of full-IPN and semi-IPN hydrogels were tested by Fourier Transform Infrared Spectroscopy (FTIR). Morphological test was done by using Scanning Electron Microscope/ Energy Dispersive X-ray Spectroscopy (SEM/EDX). Thermal properties were examined with Differential scanning calorimeter (DSC) analyzer and Thermogravimetric analysis (TGA). The mechanical analysis was performed with Zwick Universal Testing Machine. Thermal and mechanical stabilities of full-IPN hydrogel was higher than semi-IPN. The efficiency of adsorption parameters (contact time, initial feed concentration, and pH) on Chromium (VI) ion adsorbing property of Full-IPN hydrogel was also determined. Isotherms were explained with the Langmuir or Freundlich equations. According to the results of both isotherms, it can be said that the hydrogel surface was homogeneous, and the adsorption of Chromium (VI) occurred in a monolayer.

Synthesis and properties of collagen-g-poly(sodium acrylate-co-2-hydroxyethylacrylate) superabsorbent hydrogels

Novel biopolymer-based superabsorbent hydrogels were prepared by grafting crosslinked poly(acrylic acid-co-2-hydroxyethyl acrylate) (PAA-co-PHEA) chains onto collagen backbones through a free radical polymerization method. The graft copolymerization reaction was carried out in a homogeneous medium and in the presence of ammonium persulfate (APS) as initiator and N,N '-methylene bisacrylamide (MBA) as crosslinker. A proposed mechanism for collagen-g-(PAA-co-PHEA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy and TGA thermal analysis. Moreover, the morphology of the samples was examined by scanning electron microscopy (SEM). The effect of concentration of MBA as well as AA/HEA weight ratio on the swelling capacity of the hydrogel was also studied. Furthermore, the water absorbency of hydrogels was measured in solutions with pH ranging 1 to 13. The collagen-based hydrogel exhibited a pH-responsive character, so that a swelling-deswelling pulsatile behavior was recorded at pHs 2 and 8. Preliminary swelling and deswelling behaviors of the hydrogels were also studied. Additionally, the hydrogels exhibited salt-sensitivity and cation exchange properties.

Improved Conductivity of Polysaccharide-co-Polyacrylate/Polyaniline Conducting Hydrogels

In this article, three families of polysaccharide-co-polyacrylate copolymer hydrogels were synthesized by free radical polymerization. The water absorbencies of the starch-co-polyacrylate, alginate-co-polyacrylate and chitosan-co-polyacrylate hydrogels were 1170, 1190 and 1350 g/g, respectively. The influences of crosslinker, initiator, neutralization degree, monomer concentration and the polysaccharide dosage on the water absorbency of the hydrogels were thoroughly investigated. The molecular structures, thermal stability and morphology of the copolymer hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). To improve the conductivity, polysaccharide-co-polyacrylate/polyaniline conducting hydrogels with interpenetrating network structures were produced by in-situ polyaniline of aniline based on the high water absorbency of the copolymer hydrogels. The novel conducting hydrogels present good electrical and electrochemical behaviour, which makes them potentially useful in supercapacitors, biosensors, bioelectronics, solar cells and memory devices.

Effect of cross-linker and initiator concentration on the swelling behaviour and network parameters of superabsorbent hydrogels based on acrylamide and acrylic acid

Poly (acrylamide-co-acrylic acid) [poly (AAm-co-AAc)]-based hydrogels were prepared by varying the cross-linking agent concentration (NMBA) in the range of 0.0077% to 0.077%. The effect of the NMBA content on swelling parameters, such as water absorbency, swelling ratio on the hydrogel was studied by keeping two monomers content, that is, AAm and AAc constant. The effect of KPS as an initiator in the range of 0.1% to 0.5% on the water absorbency of the hydrogels was also studied. The swelling value could be modulated in a great range by varying the cross-linking agent (NMBA) or initiator (KPS) concentration at fixed monomer concentration. The synthesized hydrogels were characterized by FTIR, SEM and network parameters, such as average molecular weight between cross-links (Mc), cross-link density (q) and mesh size (ξ). The experimental results showed that the equilibrium water absorbency decreases from 707.23 to 389 with increasing the NMBA content from 0.0096 % to 0.0385%. The network parameters, such as average molecular weight between cross-links (Mc) were decreased from 2.33 × 1012 to 2.30 × 1011 and cross-link density (q) decreased from 3.07 × 10−11 to 3.09 × 10−11; although mesh size (ξ) increased from 3.00 × 106 to 8.89 × 106 with increase in percentage of NMBA content from 0.009265% to 0.077%. The equilibrium water absorbency of various hydrogels were studied in distilled water and different types of saline solutions, which exhibited that hydrogels have higher equilibrium water absorbency in 0.009% saline (NaCl) solution than in 0.09% and 0.9% saline solutions. From the results it was clear that water absorbency increased from 302 to 573 g water/g sample with increasing the KPS content from 0.1 to 0.5%.