In situ atomic force microscopy measurement of the dynamic variation in the elastic modulus of swollen chitosan/gelatin hybrid polymer network gels in media of different pH

The surface morphology and elastic modulus of chitosan/gelatin hybrid polymer network (CS/GLN HPN) gels was investigated by in situ atomic force microscopy (AFM). The surface domains of hydrogel varied from irregular clumps to sponge-like patterns with increasing swelling time. The vertical height and width of the surface domains observed in alkali medium are smaller than in acidic medium. The indentation of the gels caused by the AFM tip increased with time and the elastic modulus of the gels estimated by the Hertz model decreased sharply compared with that of xerogel. In alkali medium, due to the reassociation of hydrogen bondings between networks, the elastic modulus increased slightly. © 1999 Society of Chemical Industry