Surfactant diffusion through bicontinuous micellar networks: a case study of the C9G1/C10G1/H2O mixed surfactant...

Self-diffusion coefficients were obtained by means of NMR diffusometry for differing ratios of n-decyl-beta-D-glucopyranoside (C10G1) and n-nonyl-beta-D-glucopyranoside (C9G1) surfactant mixtures, along dilution lines through the micellar region of the ternary C9G1/C10G1/H2O phase diagram. Networks of bicontinuous micelles have been suggested to exist throughout the micellar regions of the phase diagram. A phase separation into two coexisting liquid solutions is observed in the dilute, C10G1-rich regions of the phase diagram. The fact that the dilution curves follow scaling relations pertaining to surfactant diffusion in a network for mixtures rich in C10G1 indicates that the phase separation is due to differences in the networks in different micellar regions of the phase diagram; networks remain largely intact despite dilution down to the phase separation in the C10G1-rich region, whereas networks with scissions are predicted to exist in the C9G1-rich regions of the micellar phase.