Comparison of the mesh size for semi-dilute worm-like micelles obtained through rheology, neutron scattering, cryo-TEM, and theory.

Worm-like micelles (WLMs) are amphiphilic structures that display viscoelastic properties due to entanglement of robust thread or hair-like morphology. In the semi-dilute regime, the properties of wormlike micelle solutions are no longer governed by the features of individual micelles but rather by the emergent inter-micellar structure reflected in a transient network characterize by the mesh size. A new approach was developed to obtain the mesh size information from small-angle neutron scattering (SANS) data. This observed mesh size was compared with those obtained through rheology, cryo-TEM and by theory. The different physical origins of these values are discussed. The corresponding osmotic pressure was also calculated based on the mesh size from SANS at various salt concentrations and temperatures. It was used to predict concentration and thermal critical points which correspond with observed phase separation. Reasonable agreement was found for the dynamic, structural, and theoretical mesh size, sufficient to support structural interpretations of rheological data which form a basis for theoretical predictions of the complex rheology displayed by WLM systems.