The polymorphism of three members of the homologous series hexa(p-alko
xyphenoxymethyl) benzene (benzene pizzanes) with 5, 6 and 7 carbons in
the alkoxy chains and several of their deuteriated isotopomers have b
een investigated by differential scanning calorimetry, polarizing opti
cal microscopy, X-ray diffraction and deuterium NMR spectroscopy. Thes
e homologues exhibit several solid phases and a high temperature M pha
se, which is isomorphic in the three homologues and whose nature is di
scussed. In the solid phases, the benzene cores of the molecules remai
n rigid, but the side chains are mobile, as reflected by rapid pi-flip
s of the benzene rings in the side chains. It is found that there are
two types of such benzene rings, differing in the rates of flips. In t
he M phase the molecules undergo fast overall reorientation and the si
de chains are even more disordered than in the solid phases. However t
he X-ray measurements do not provide a clear cut determination as to w
hether this phase is crystalline or mesomorphic. Mixing of the benzene
pizzanes with p-xylene yields lyomesophases, which appear to belong t
o the D-ho class.