Dynamic viscoelasticity and small-angle X-ray scattering studies on the gelation mechanism and network structure of curdlan gels

Small-angle X-ray scattering (SAXS) and dynamic viscoelasticity measurements were carried out to clarify the static network structure of curdlan gels in 0.01 N NaOH at the semi-dilute regime. The structural change during the gelation was also investigated by time resolved measurement with a temperature jump procedure. It was revealed from the time resolved SAXS measurements that the gelation occurred via a structural change from a heterogeneous network structure to a homogeneous network structure. The structural change at the semidilute regime would be correlated to the dissociation of the molecular associations, from an associated state to a dissociated state, at the dilute regime. It was also revealed from the results of SAXS measurements that the network structure of curdlan gel is characterized by a mass fractal structure with the fractal dimension of 1.4. It was clarified by a scaling theory that the curdlan gel consists of a homogeneous network structure. It was shown that the distance between the neighboring cross-linking points could be related to the correlation length determined by the SAXS measurement