Phase Transition between the Cholesteric and Twist Grain Boundary C Phases

The upper critical temperature Tc2 for the phase transition between the Cholesteric phase (N*) and the Twist Grain Boundary C phase with the layer inclination tilted to the pitch axis (TGBct) in thermotropic liquid crystals is determined by the mean field Chen-Lubensky approach. We show that the N*-TGBct phase transition is split in two with the appearance of either the TGBA or the TGB2q phase in a narrow temperature interval below Tc2. The latter phase is novel in being superposed from two degenerate TGBct phases with different (left and right) layers inclinations to the pitch axis.Comment: Phys. Rev. E, to be publ; 24 pages, RevTeX + 3 ps figure

Nouvelle forme de débat pour un empowerment citoyen de la transition énergétique

International audienc

Nouvelle forme de débat pour un empowerment citoyen de la transition énergétique

International audienc

Piezothermal analysis of the NRe_{\rm Re}-SAd_{\rm Ad} transition on small samples of p-octylbenzoate p-cyanobenzoyloxyphenyl

In order to detect weakly first-order phase transitions by means of piezothermal measurements on small samples of calamitic mesogens exhibiting reentrant phenomena, a new high pressure calorimeter equipped with a composite slab thermostat has been built. Its efficiency has been proved and its performances determined. Its use on a ten cubic millimeter effective volume of p-octylbenzoate p-cyanobenzoyloxyphenyl has permitted to prove the N$_{\rm Re}$-S$_{\rm Ad}$ transition is not purely second order but weakly first-order