Gelation of Freely Associating Single-Wall Carbon Nanotube Networks*

We report on the rheological evolution of a model filamentous network comprised of a semidilute dispersion of Single-Wall Carbon Nanotubes (SWNT). Using microrheology, we follow the gelation of a surfactant stabilized SWNT suspension from an initial sol of contacting but unbonded SWNT, endpointing in a gel network with a finite, zero-frequency elastic modulus. The SWNT network exhibits all the hallmarks of a critical sol-gel transition, including divergence of the viscosity as the gel point is approached from below, emergence of a finite elastic shear modulus above the gel point, and power law scaling of the viscosity and shear modulus below and above the gel point, respectively. The viscoelastic moduli exhibit a remarkable collapse under time-cure superposition, a footprint of self-similarity in inter-tube bond connectivity. Additionally, we present a scheme to spatially map rheological inhomogeneities in the network during gelation.