Critical behavior at the nematic to lamellar phase transitions: A synchrotron x-ray scattering study

Abstract

The nematic $(N)$ to lamellar ${(L}_{\ensuremath{\alpha}})$ phase transition in binary mixtures of cesium-perfluoro-octanoate (CsPFO) and water has been studied by high-resolution synchrotron x-ray scattering at 46.6 weight % CsPFO. The longitudinal correlation length ${\ensuremath{\xi}}_{\ensuremath{\parallel}}$ and the susceptibility \ensuremath{\sigma} associated with the lamellar phase fluctuations in the $N$ phase, measured over three decades of reduced temperature, diverge with critical exponents ${\ensuremath{\nu}}_{\ensuremath{\parallel}}=0.86\ifmmode\pm\else\textpm\fi{}0.04$ and $\ensuremath{\gamma}=1.37\ifmmode\pm\else\textpm\fi{}0.11,$ respectively. These results show that the $N$ to ${L}_{\ensuremath{\alpha}}$ phase transition is quantitatively similar to the $N$ to smectic-$A$ phase transition of thermotropic liquid crystals with a wider nematic range.