MOLECULAR DESIGN OF AMPHOTROPIC MATERIALS - DOUBLE-HEADED DIOL-BASED MESOGENS INCORPORATING RIGID STRUCTURAL UNITS

The syntheses of novel bolaamphiphilic triol and tetraol compounds inc orporating rigid structural units are described. Their liquid-crystall ine properties were investigated by polarizing microscopy, differentia l scanning calorimetry and in some cases also by means of X-ray diffra ction. Most 4,4-disubstituted biphenyl derivatives exhibit one or more smectic phases (predominantly S(A) but also S(C), S(B), S(G) and S(K) ) and extraordinarily high clearing temperatures. No thermotropic liqu id-crystalline properties could be detected for bolaamphiphiles incorp orating a single 1,4-disubstituted phenyl ring or a 2,6-disubstituted naphthalene ring system, but for naphthalene derivatives a lyotropic s mectic A phase was induced by addition of water. If one of the diol gr oups of the biphenyl-derived bolaamphiphiles is replaced by a single h ydroxy group or by a carboxylic acid group the mesophase stability is decreased. Mesomorphic properties are lost if the hydrogen-bonding den sity is further diminished by the replacement of one diol group by an ethyl carboxylate group. However, in these cases lyotropic liquid-crys talline phases can be induced by the addition of water.