Original stimuli-sensitive polysaccharide derivatives/N-isopropylacrylamide hydrogels. Role of polysaccharide backbone

This article compares the properties of a novel class of unsaturated Xanthan and Gellan derivatives/N-isopropylacrylamide stimuli-responsive hydrogels synthesized by free radical polymerization. Xanthan and Gellan Gum were partially functionalized by esterification with maleic anhydride under various conditions. By copolymerization of these maleate polysaccharides with a N-isopropylacrylamide known temperature sensitive precursor, water-swollen hydrogels with interpenetrating polymer networks (IPN) were obtained. The hydrogels were characterized for their temperature and pH-responsive behaviour by equilibrium swelling experiments and differential scanning calorimetry. The investigation of these materials also includes solid-state 13CP/MAS NMR and elemental analysis of the nitrogen content. Morphology was visualized by scanning electron microscopy. Depending upon composition and the nature of the base-polysaccharide, the hydrogels showed different response rates to the external changes of temperature as well as pH. By changing the feed composition ratio of precursors and crosslinking agent (β-cyclodextrin acrylate or N,N′-methylenebisacrylamide respectively) the phase transition temperature (lower critical solution temperature) could also be adjusted near to the body temperature for biomedical and biotechnological applications. The role of the rigidity and the charge density of the polysaccharide chain, its ability to form hydrogen bonding on these properties are more particularly considered.