Electron microscopy of the two-dimensional fluid antiphaseSÃ

We have applied the freeze-fracture technique to polar liquid-crystalline systems in which there exists a fluid antiphase $S_{\tilde{A}}$ and a bilayered smectic $S_{A_2}$. In the case of the $S_{\tilde{A}}$ phase the electron microscope gives (i) a definite evidence of the two-dimensional array of this mesophase and (ii) the first proof that the antiphase domains are separated by real walls. In the case of $S_{A_2}$ the smectic layered structure is seen for the first time in a thermotropic mesogen and in a fluid mesophase.