Pyramidic mesogen

Fig. 1 Cores of star-shaped mesogens. Mesogens point to the vertices of a triangle (A-D), a trigonal pyramid (E-J), a tetrahedron (K-N) or a distorted tetrahedron (O), a hexagon (P, R), a truncated triangle (Q, S), a trigonal prism (T), a truncated square (U), a cube (V) and a distorted icosahedron (W)...

Pyramidal or bowlic mesogen - a mesogen composed of molecules derived from a semirigid conical core. 

Fig. 2.1. Typical molecular structures, (a) Rod-like mesogens (i) p-azoxyanisole (ii) p -n-hexyloxybenzylidene-p-n-hexyl oxyaniline. (b) Discshaped mesogens (i) hexa-substituted esters of benzene (ii) hexa-substituted esters or ethers of triphenylene " (iii) hexa-n-alkanoates of truxene. (c) Phasm-like mesogens bis-(3,4,5-trialkoxybenzoyloxy)4 -phenyl terephthalates. (d) Pyramid-like mesogens (i) hexa-substituted tribenzocyclononanef (ii) octa-substituted tetrabenzocyclododecatetraene. ...

As already mentioned, mesogens embrace a diversity of structure. We shall not, however, be concerned here with mesophases of disc-, pyramid-and phasm-like molecules, but shall confine attention to thermotropic mesomorphism exhibited by LMM compounds with elongated and relatively rigid lath-like molecules. Mesophases formed on heating such compounds are classified into three types nematic, cholesteric, and smectic. There are more than ten recognized smectic modifications and these are denoted by Sa, Sb, Sc-.-Sl- A description of the structural features of these phases may be found in standard books and reviews " and it is my intention in this section to bring the information on this subject up to date and to present it in a more concise form. 

---