Synthesis and studies of some cholest-5-en-3-ol-(3 beta)[4-phenylpyridylazo]carbonate-containing supramolecular hydrogen-bonded mesogens

Mesogenic materials containing cholest-5-en-3-ol-(3 beta)[4-phenylpyridylaz o]carbonate (CPPC) and 4-n-alkyloxybenzoic acids have been synthesized usin g hydrogen bonding as a mechanism for self-assembly. Phase diagrams of the binary mixtures of the hydrogen bond donor and acceptor were established us ing polarizing optical microscopy. The maximum isotropization point was obs erved for the 50 mol % composition confirming the formation of stable 1 : 1 complexes due to intermolecular hydrogen bonding. All the supramolecular a ssemblies built from 1 : 1 molar ratios of the hydrogen bond donor and acce ptor moieties exhibit well defined smectic A (SmA) liquid crystal phases on heating and cooling cycles. The SmA phases exhibited by the complexes are not observed for the individual components. The azobenzene moiety of CPPC u ndergoes trans-cis-photoisomerization with a quantum yield of 0.1 and the a ctivation energy for the thermal cis-trans-isomerization was estimated as 9 2 kJ mol(-1).