DYNAMIC VISCOELASTIC COMPARISON OF CHEMICAL AND PHYSICAL GELS

The dynamic viscoelastic behavior of TEOS (tetraethoxysilane) and gela tin during the sol-gel transition is compared. Different profiles of d ynamic storage modulus G' and loss modulus G'' with time are seen. Gel ation time t(gel) is determined from the frequency independent tan del ta = G''/G' for both systems. During the period following the gelation point, a transition in the scaling exponent of G' with (t - t(gel)) i s seen. For TEOS, the exponent changes from 0.494 to 5.24, for gelatin , from 0.24 to 2.11. The percolation model is used to qualitatively ex plain the differences in different networks.