Figure 2. Mechanical properties of composites with semi-flexible PIC networks and rigid CNT rods.

(a,b) Frequency sweeps in the linear viscoelastic regime (a) and in the nonlinear regime at a pre-stress σ₀=40 Pa (b). The colours are indicated in the legend; the concentrations: c_PIC=1.0 mg ml⁻¹ (all samples), c_SWCNT=0.2 mg ml⁻¹, c_MWCNT=0.5 mg ml⁻¹, c_short-SWCNT=0.2 mg ml⁻¹. (b) Differential modulus at frequency ω=1 Hz at the same concentrations as in a,b. (c–g) Stiffness of PIC/CNT composites in the linear regime represented by the differential modulus K′ at σ=0 Pa (e,g) and the nonlinear regime represented by K′ at σ=40 Pa or σ=100 Pa (d,f) for gels with PIC concentrations of 1.0 (d,e) and 2.5 mg ml⁻¹ (f,g), respectively. (h) The critical stress σ_c decreases with nanotube concentration for gels with PIC concentrations of 1.0 and 2.5 mg ml⁻¹. Note the logarithmic scale on the y axis. (i) The critical strain γ_c also decreases with increasing nanotube concentrations. The effects are strongest for the gels with long single-walled CNTs and low PIC concentrations. The error bars represent s.d.'s over two samples.