Thermal, swelling and stability kinetics of chitosan based semi-interpenetrating network hydrogels (original) (raw)
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TURKISH JOURNAL OF CHEMISTRY, 2021
In the last few decades, acrylic acid-chitosan amphiphilic superabsorbent hydrogels have received great research interest because these hydrogels can uptake a large amount of water and have antibacterial activities [1, 2]. Due to their excellent properties, chitosan-acrylic acid hydrogels play a key role in wastewater treatment [3, 4]. Chitosan has been known as a renewable biopolymer with considerable biocompatibility, biodegradability, antimicrobial activity, etc. Its properties can be altered under mild conditions due to its reactive amino and hydroxyl group [5]. However, the swelling ratio of chitosan is high just at a low pH value. Introducing poly(acrylic acid) is a potential role to amend the swelling degree of chitosan in a variety of pH values [6]. Ge et al. [7] synthesized the superabsorbent polymer based on chitosan-acrylic acid using the thermal reaction. Shim and coworkers [8] prepared Gamma irradiated poly(acrylic acid)-chitosan hydrogels for the purpose of increasing the drug release aptitude. They reported that release behavior of the drug, 5-fluorouacil from the hydrogel was different based on the pH value of the medium, monomer percentage, and the radiation dose. Zheng et al. [9] investigated the recovery of a valuable metal Ni 2+ using aqueous dispersion polymerized chitosan-acrylic acid hydrogel. They observed that the prepared absorbent had a good affinity to Ni 2+. Also, it is observed that chelation interaction among the carboxylated group, and Ni 2+ is the main mechanism of absorption. Today, numerous kinds of hydrogels have been formed. Among them, amphiphilic semi-interpenetrating networks (semi-IPN) have been extensively favored because of their excellent properties [10-12]. Marjub et al. [13] used Acrylic acid-chitosan semi-IPN hydrogel for copper (II) and lead (II) ions adsorption from waste water. Torrado and coworkers [14] investigated the drug release behavior of PAAc-chitosan hydrogels. In semi-IPN hydrogels, each polymer network retains its individual characteristics like its homopolymer as well as, when one portion shrinks or swells, another portion could be created for supporting via repulsive and attractive interaction of the whole network. It is noteworthy that when an amphiphilic semi-IPN hydrogel swells, the network can constitute hydrophobic interaction, suggesting the reduction of the swelling degree of the hydrophilic network [15-17]. The aim of this study was to synthesize amphiphilic semi-IPN hydrogels based on acrylic acid and chitosan and characterize their swelling behavior. For this purpose, free radical polymerization was performed using AIBN as a free
Materials Chemistry and Physics, 2012
A semi-interpenetrating polymer network (semi-IPN) based on poly(dimethylsiloxane) and poly [2-(dimethylamino)ethyl methacrylate] (PDMAEMA) was prepared. The material obtained was characterized by infrared spectrometry, differential scanning calorimetry, thermogravimetric analysis and scanning electronic microscopy. The results indicated the presence of PDMAEMA into the semi-IPNs. Only the network with the highest amount of crosslinker [(3-chloropropyl)trimethoxysilane] was stable in water. To evaluate the hydrophilic/hydrophobic character of the obtained material, swelling measurements were performed for the stable network in water and in toluene. The semi-IPN was able to adsorb about 34 % in mass of water, indicating that an appropriate hydrophylic/ hydrophobic balance was obtained. That behavior is desirable since the material was designed for metal adsorption from aqueous medium, without a lost in the ability to swell in less polar solvents.
E-Journal of Chemistry, 2011
Hydrogel films of chitosan (Cs) and agar blends of various proportions were prepared using physical solution blending. Some of the obtained films were ionically cross-linked by treatment with calcium chloride solution. The obtained films were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA), differential scanning calorimetery (DSC) and universal mechanical tester. The non-crosslinked Cs/agar blended films showed lower water swelling, melting temperature, stiffer and less elastic properties than that of pure Cs films and higher than pure agar films. Crosslinked blended films displayed further reduction in the swelling and melting temperature while maintained more hydrogel stability.
Physically and chemically cross-linked hydrogels were prepared using polyvinyl alcohol (PVA) in combination with chitosan (CH), pectin (PE), alginate (AL) and polyacrylonitrile (PAN) and characterized for their physical properties. The physically cross-linked hydrogels were prepared by applying freezing and thawing technique and their responses were compared with hydrogels cross-linked with glutaraldehyde (25%). The structures of hydrogels were characterized by recording their IR spectra and mechanical strengths were evaluated as young's modulus and elongation at break. The PVA hydrogels with different polymers have shown significant variations in their mechanical properties and found to be responsive toward solution pH. The water sorption capacity and degree of swelling (DS%) of hydrogels are found to be dependant on solution pH and temperature. Thermal properties of hydrogels were analyzed using differential scanning calorimetric (DSC), and thermogravimetric (TGA) analysis. The polymer blended PVA hydrogels are found to be thermally stable as compared to pristine PVA hydrogels. The glass transition temperature (Tg) of polymer blended hydrogels is found to be significantly higher in comparison to pristine PVA hydrogels. The scanning electron micrographs have indicated homogeneous morphologies for polymer blended PVA hydrogels and surface porosity on cross-linking is considered responsible for the uptake of water and other biological fluids.
Swelling Modelling and Kinetics Investigation of Polymer Hydrogel Composed of Chitosan-g-(AA-AM)
Egyptian Journal of Chemistry, 2021
Swelling is one of the distinct properties and a significant parameter in the characterization of the crosslinked hydrogels. Swelling investigation at different temperatures was conducted for the produced hydrogel of chitosan grafted acrylamide/acrylic acid. Peleg's model is a two parameters model, which can be used to describe the absorption of water or swelling. The data show that the swelling degree increases with temperature until it reaches 60°C, after which it decreases as the temperature rises higher. At RT, 30, 40, 60, and 80 °C, the swelling degree values of 1.4, 1.5,1.4, 2.3 and 0.7 g water/g dry hydrogel were observed after 8 hours. The applied models provided a good agreement with the experimental data with high values of the coefficient of determination (2). The observed F values and the standard error indicate the validity of the proposed model to describe the swelling of hydrogel at different temperatures. The swelling rate and swelling degree can be expressed using a 4 th degree polynomial. It was concluded that the exponential association equation model represents swelling characteristics better than the others.
This paper describes the synthesis and physicochem-ical characterization of Poly(N-isopropylacrylamide)-Chitosan-Poly(Acrylic acid) [PNIPAAm-CS-PAA] based polymeric microgels. Three different samples of multi-responsive (PNIPAAM-CS-PA) microgels were synthesized using various amounts of N N-Methylene bis-acrylamide (MBA) and Acrylic acid (AA) by free radical emulsion polymerization. The redox initiator Ammonium per sulfate (APS) was used to initiate the reactions while MBA was used as a crosslinking agent. The purified polymeric microgels were then characterized using UV-Visible spectroscopy, Fourier transform infrared spec-troscopy (FT-IR), Laser light scattering (LLS), Ostwald viscom-etry, dynamic Rheology and swelling/de-swelling measurements. From the spectroscopic result it was observed that all the reactions have been completed and the resultant microgels were successfully synthesized. The influence of various parameters such as, chemical composition and some external stimuli like temperature and pH on the physicochemical behavior of polymeric microgels was investigated through visual stability test, laser light scattering, viscometry and rheological measurement. The LLS analysis was performed to deduce the size, in the terms of hydrodynamic radius (R h), of the microgel samples in aqueous media at different pH and temperature. From LLS analysis the microgels were found to be stable at all pH values above the pKa values (4.2) of AA in temperature ranges from 20 °C to 50 °C. With rising in temperature and pH causes aggregation of particles and decrease in stability of microgels due to the decrease in hydrophobicity. From the Rheological measurements, various physiochemical properties such as, elasticity , viscosity, shear stress, storage modulus, loss modulus, phase angle and complex viscosity of the microgels were gathered. The Ostowald viscometry was used to measure the flow viscosity of microgels at different pH and temperatures. The present observations reflect that the prepared samples are multi-responsive and their physicochemical behavior can be tuned very easily by changing their composition and/or varying the external stimuli.
Journal of Applied Polymer Science, 2015
Two series of pH-sensitive semi-interpenetrating network hydrogels (semi-IPN) based on chitosan (CS) natural polymer and acrylamide (AAm) and/or N-hydroxymethyl acrylamide (HMA) monomers by varying the monomer and CS ratios were synthesized by free radical chain polymerization. 5-Fluorouracil (5-FU), a model anticancer drug, has been added to the feed composition before the polymerization. The characterization of gels indicated that the drug is molecularly dispersed in the polymer matrix. The swelling kinetics of drug-loaded gels have decreased with increased HMA content at 37 C in both distilled water and buffer solutions with a pH of 2.1 or 7.4. Elastic modulus of the gels increased with the increase in HMA content and higher CS concentration enhanced the elastic modulus positively. Moreover, cumulative release percentages of the gels for 5-FU were ca. 10% higher in pH 2.1 than those in pH 7.4 media. It was determined that they can be suitable for the use in both gastric and colon environments. V C 2015