Synthesis and physicochemical investigation of chitosan-PMAA-based dual-responsive hydrogels
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Chitosan-based (chitosan-poly(methacrylic acid)) responsive hydrogels were synthesized using different gel compositions and at various pH values and temperatures in an aqueous medium, and the physicochemical properties (swelling/de-swelling, electrical properties, colloidal stability, and volume phase transitions) of these hydrogels were investigated. Chitosan-PMAA hydrogels with different compositions were synthesized using the free-radical copolymerization method in an aqueous medium at 70 °C. The synthesized microgels were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and based on their zeta potentials. FTIR was used to determine the chemical structure of the copolymer hydrogel. DLS was employed to measure the hydrodynamic diameters of the microgels in water at different pH values and temperatures. The electrokinetic properties of the gel were investigated using the zeta potential. The equilibrium swelling/shrinking ratios and the volume phase changes (induced by pH and temperature variations) of the microgels were found to be composition-dependent. Most of the properties of the microgels changed with variations in the physicochemical conditions of the medium used. It was found that the swelling ratios of the microgels increased with pH. An increase in the size of the microgels with temperature was also observed. A clear transition from sol to gel behavior with increasing temperature above 55 °C was also noted.
KeywordsChitosan Hydrogels Responsive gels Physicochemical properties Volume phase changes Dynamic laser light scattering Zeta potential
Dr. Abbas Khan is highly grateful to The World Academy of Sciences (TWAS, for the advancement of science in developing countries) and USM for a TWAS-USM postdoctoral research fellowship. He also wishes to acknowledge Abdul Wali Khan University Mardan Pakistan for his postdoc study leave. The authors also wish to thank the Ministry of Science, Technology and Innovation (MOSTI) of Malaysia for sponsoring the project under the Fundamental Research Grant Scheme FRGS/203/PBAHAN/6071242.
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