Thermal–mechanical behaviour of chitosan–cellulose derivative thermoreversible hydrogel films

Hydrogels are high water content materials prepared by polymer crosslinking that are able to release active species, such as therapeutic, antibacterial, antiperspirant and moisturising agents, and fragrances. In recent years, several hydrogel systems have been reported based on both natural and synthetic polymers. Among the natural polymers, chitosan and cellulose-derivatives have been extensively studied, due to their stimuli responsive properties (pH and temperature sensitivity, respectively). In this work, we have developed physically crosslinked hydrogel films based on chitosan (CH) and (hydroxypropyl)methyl cellulose (HPMC). These films were prepared by two methodologies: solvent casting and freeze–thaw techniques. The resulting membranes, were assessed in terms of thermal (DSC and TGA), mechanical (stress–strain mechanical assays and DMA) and structural (X-ray) properties. The obtained results indicate that the developed CH:HPMC membranes show a good compatibility between the two component biopolymers. Additionally, these materials display an excellent thermal stability (having a T_{Decomposition} > 270 °C), good mechanical properties (especially for the compositions with similar contents of both polymers), a glass transition temperature (T_g) higher than 194 °C and predominate amorphous character. The described characteristics turn the designed CH:HPMC membranes suitable candidates as active species carriers, for the envisaged textile application.