Synthesis and characterization of novel pH‐sensitive chitosan‐poly(acrylamide‐co‐itaconic acid) hydrogels

Abstract

Novel pH-sensitive chitosan-poly(acrylamide-co-itaconic acid) hydrogels were prepared by free radical copolymerization of acrylamide and itaconic acid (IA) in chitosan solution. The hydrogels were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and the swelling ratios of the hydrogels in water (pH 6.8) and pH 1.2. The influence of composition on the thermal properties of the hydrogels was assessed. The glass transition temperatures of the samples increased with IA content, ranging from 110 to 136 ∘ C. Swelling of the hydrogels was found to obey second-order kinetics with respect to the remnant swelling, indicating that diffusion is controlled by the relaxation of chains. The equilibrium swelling degree was strongly dependent on pH and composition. At both pH values the highest water uptake was obtained for the IA-free sample M1. From the equilibrium swelling results the average molar mass between crosslinks, M c , and the crosslink density of the chitosan-poly(acrylamide-co-itaconic acid) samples were calculated. The results evidenced the reinforcing effect of IA on the hydrogel structure. It is concluded that these highly swellable pH-sensitive hydrogels can be useful for applications in biomedicine and pharmacy.

Synthesis and characterization of pH and temperature responsive poly(2-hydroxyethyl methacrylate-co-acrylamide) hydrogels

“…As expected, the swelling capacity of the copolymer hydrogels increased with increasing their AAm content and they all exhibited the same basic hydrolysis effect on swelling at pH higher than 6, which became more significant as the AAm content in the hydrogel increased. A similar hydrolysis effect on swelling has been reported for other acrylamide based hydrogels [24] .…”

An Optical Urate Biosensor Based on Urate Oxidase and Long-Lifetime Metalloporphyrins

“…In addition to the presence of amide side groups, the exponential increase in swelling upon the addition of acrylamide may also be due to the partial hydrolysis of the moiety, which has been observed in pHs of 6 and above. Specifically, the formation of negatively charged carboxylate ions following acrylamide hydrolysis can lead to greater elastrostatic repulsion within the gel and increased hydrogel swelling [40,41].…”

pH-sensitive interpenetrating network hydrogels based on pachyman and its carboxymethylated derivatives for oral drug delivery

“…Hydrogels contain a highly hydrated, three-dimensional network and are known for their biocompatibility and biodegradability as well as security [5,6], which is gaining increased attention because of their great potential in drug delivery systems, tissue engineering applications, wound healing, bioseparation, and so on [7][8][9][10][11]. Moreover, hydrogels with environmental sensitivity could respond to surrounding changes such as pH, temperature, ionic strength, and electric current [12][13][14][15]. In designing hydrogels for controlled drug release, pH sensitivity is an important factor in the gastrointestinal tract [16,17].…”