Location of the discotic lamellar-nematic tricritical point and isotope effects in the caesium pentadecafluorooctanoate (CsPFO)/water system as established by133Cs N.M.R. spectroscopy

133Cs N.M.R. spectroscopy has been used to locate the discotic lamellar (smectic A)-nematic tricritical point in the CsPFO/H2O and CsPFO/2H2O systems. In both systems this occurs at the same volume fraction of 0·25, but at different temperatures (302·05 and 304·80 K, respectively). The phase diagram for the CsPFO/H2O system has also been studied for the first time and a comparison of the corresponding fixed points shows there to be large isotope effects.