Phasmid and biforked mesogens with thiobenzoate end groups

Phasmids and Polycatenar Mesogens

“…2). Actually, that is consistent with the weak transition heats measured between lamellar and columnar mesophases in various series (about 1 kJ mol-'): non-drastic structural changes occur between the different mesophases, as is suggested by the permanence of an angle near to 60" in the various mesophases as well as in the crystalline state [49]. The nematic phase observed with polycatenars has the optical properties of the classical bicatenar nematic.…”

“…In addition to the influence of the core linkagesangles, dipole sense (see for example Table 5 and the literature [49]) -on the appearance of columnar mesomorphism, this arrangement is also quite sensitive to the presence of lateral groups on the core. Compounds 43 with two methyls and 44 with two chlorine atoms, for instance, do not display any columnar mesomorphic organization.…”

Column Correlation in Polycatenar Mesophases

“…For the mesophases studied in a planar orientation with the columns subjected to a normal dilation, we can predict the undulation instability of columns by minimizing the elastic free energy, by taking into account the symmetry of the arrangement of the columns in a hexagonal network. Thus, with previous calculations that describe the undulations of the smectic layers and of the columns in the columnar–hexagonal mesophases,11, 16, 21, 26, 27 we derive Equations (1–3), , , where m, K 3 , B , δ c , and λ are, respectively, the De Gennes characteristic length, the curvature elastic constant, the elastic modulus, the threshold dilation, and the curvature wavelength. $\rm{{\it m}\,=\,\left({{{\it K}_{3}} \over {{\it B}}}\right)1/2}$ δ c = 2π m λ 2 = 4π md …”

“…Indeed, several viscoelastic properties have been examined and many typical constants have been measured. Furthermore, an interesting comparison of mechanical behaviors have been made between the columnar–discotic mesophases, the smectic layers and the columnar–lyotropic liquid crystals 10–21…”

Chemical Structure and Mesogenic Properties

“…Cyclohexane rings have also been introduced into tetracatenar com- pounds [21], and ester groups have been exchanged for thioester groups [2121. An X-ray investigation of the solid state of a thioester compound [212] has shown the nearly parallel orientation of the long-chain substituents, and the smectic C like lamellar structure, which is typical of a segregation of an aromatic core and aliphatic flexible substituents.…”