Stability of the columnar and smectic phases of length-bidisperse parallel hard cylinders

Szabolcs Varga (1) , Enrique Velasco (2) , Luis Mederos (3) , Franz J Vesely (4)

1 Institute of Physics
2 DFTMC - Departamento de Física Teórica de la Materia Condensada [Madrid]
3 ICMM - Instituto de Ciencia de Materiales de Madrid
4 University of Vienna [Vienna]

The effect of length-bidispersity on the stability of nematic, smectic and columnar phases of rod-like particles is studied in the perfect alignment limit using the Onsager's second virial theory. Three different smectic structures are observed: (i) the conventional smectic (S1) phase, where both components accommodate in the same layer; (ii) the microsegregated smectic (S2) phase, which can be considered as an alternation of fluid layers rich in short and long rods, respectively; and (iii) two layers of short rods accommodate inside one layer of long rods, which gives the third smectic (S3) structure. With decreasing length ratio () the smectic phase is destabilized with respect to the nematic phase at compositions rich in short rods and two forms of smectic phases, namely S1 and S2, take place in alternation. The alternation of the structure is the consequence of the minimization of the number of overlapping layers of the short rods with one long rod. In mixtures rich in long rods, the short and long rods are in the same layer up to l=0.39, while the short rods can accommodate into the interstitial region of long rods for l<0.39 and the system forms a S2 phase. The S3 phase is observed in the range 0.57

Mots clés: Physical Sciences

Szabolcs Varga, Enrique Velasco, Luis Mederos, Franz J Vesely. Stability of the columnar and smectic phases of length-bidisperse parallel hard cylinders. Molecular Physics, 2009, 107 (23-24), pp.2481-2492. ⟨10.1080/00268970903369180⟩. ⟨hal-00548165⟩