Fig. 1
Structure and mechanical characterization of the viscoelastic PAA gels. a Cartoon representing the association of an elastic network of PAA with a viscous solution of linear PAA to form a viscoelastic gel. Trapping of linear chains of PAA in a network of PAA leads to the formation of a viscoelastic gel. b Evolution of G’ and G” during the polymerization of a viscoelastic gel: G’ and G” both increase during the formation of the branched PAA network. G’, light gray (left axis); G”, dark gray (right axis). c Representative plot of the stress relaxation of a viscoelastic gel containing 2.75% linear polyacrylamide: evolution of the shear modulus over time under a 10% strain. d Average value of G’ as characterized by a 2% oscillating shear stress at a frequency of 0.159 Hz and 2% strain; n = 5 gels per condition. Error bars represent the standard error. e Average value of G” as characterized by a 2% oscillating shear stress at the frequency of 0.159 Hz and 2%strain; n = 5 gels per condition. Error bars represent the standard error. f Values of G’ and G” as a function of the oscillation frequency for the highly viscous gel (designed as the G’ = 5 kPa, G” = 500 Pa gel). The frequency sweep was performed from 0.005 Hz to 10 Hz. G’ shows a weak frequency dependence while G” varies over a decade in the range of frequencies probed. g Creep and recovery of the viscoelastic gel containing 2.75% of linear PAA. The creep compliance was followed during the application of a stress of 100 Pa for 50 s, and then the recovery was monitored for 50 s
