A new hexatic phase observed in biomembrane-like films 

An intermediate surface hexatic phase between the liquid and the crystalline phases has been found for the first time in a lyotropic lamellar liquid-crystal (LC) system. This phase is highly unusual in that it has long-range six-fold bond-orientational order but liquid-like nearest-neighbor positional correlations, and could represent a significant departure from our current understanding of defect-mediated melting in two dimensions. Our result represents the first report of an in-plane hydration force that is due to the existence of at least two water molecules situated between a hydrated nitrate functionality and an imidazolium-based core in adjacent molecules.