FIG. 1.
(color online) a) Depicts frequency sweeps of the differential storage (K′) and loss (K″) moduli of WT cross-linked networks under zero prestress (squares) [13] and under significant prestress (circles). The prestress data is acquired just before network rupture at ~ 9Pa. (Inset) Demonstrates the recovery of the linear mechanical response (red crosses) following measurements of nonlinear elasticity at 8.7Pa [18]. b) Depicts a contour plot of the WT ILT= K′/K″ as a function of both frequency and prestress. Individual data points are located in frequency at: 17 log-spaced points between 6.94 × 10−4 Hz and 15 Hz, and in prestress at: 0, 2, 4, 6, 8Pa. We utilize a third-order spline interpolation to fit the data to generate smooth contours. c) At intermediate levels of prestress, the plateau modulus remains unchanged (red line). However, the relaxation frequency ωR (arrows) has already decreased, demonstrating a clear separation between network stiffening and the dynamic nonlinearity which underlies SEG. d) Depicts a contour plot of the K255E ILT= K′/K″ as a function of both frequency and prestress. Individual data points are located at the same frequencies as b) and in prestress at: 0, 0.5, 1, 1.1, 1.2Pa. All of the above data is taken at R = 0.01.