Chitosan membranes exhibiting shape memory capability by the action of controlled hydration

Chitosan membranes can undergo a glass transition at room temperaturetriggered by hydration. The mechanical properties of the membranes were followed by atension test and dynamic mechanical analysis (DMA), with the sample in wet conditionsafter being immersed in varying compositions of water/ethanol mixtures. Results show thatwith the increasing of water content, the Young’s and storage modulus decreasesystematically. For water contents of ca. 35 vol%, chitosan (CHT) exhibits a glasstransition, showing an elastomeric plateau in the elastic modulus above this hydration leveland the occurrence of a peak in the loss factor. Due to the semi-crystalline nature of CHT,membranes of this biomaterial present a shape memory capability induced by water uptake.By fixation of the permanent shape by further covalent cross-linking, the membranes canhave different permanent shapes appropriate for different applications, including in thebiomedical area.This work was supported by the Portuguese Foundation for Science and Technology Foundation (FCT) through project PTDC/FIS/115048/2009