Thermoreversible konjac glucomannan gel crosslinked by borax

Dynamic viscoelastic measurements were carried out for novel konjac glucomannan/borax gels. Gel networks were formed through the crosslinking reaction between borate ions dissociated from borax and the cis-diol sites on the polysaccharide chains. At lower oscillation frequencies, the complex gels behave like a liquid, whereas at higher frequency they relax like true gel materials with a predominant elastic relaxation response. An obvious plateau value of storage modulus (G') and a maximum and minimum in loss modulus (G') were observed on the relaxation spectrum. The characteristic viscoelastic functions were studied as a function of concentrations of konjac glucomannan and borax, strain, and temperature. The storage and loss moduli obey time-temperature superposition by using the empirical shifting factors, which are corresponding to the theological properties with respect to the longest relaxation time. Relaxation and crosslinking energies for the gels were calculated from the Arrhenius representations of the shift factors. The experimental finding indicates the nature of dynamic crosslinking for the complex gels. (c) 2007 Elsevier Ltd. All rights reserved.