Synthesis and mesomorphism of 4,4 '-bis(omega-hydroxyalkoxy)-alpha-methylstilbenes

A homologous series of 4,4'-bis(omega-hydroxyalkoxy)-omega-methylstilbenes denoted HAMS-n, has been synthesized. Here n is the carbon atom length of t he peripheral M-alkyl chain; in this work n = 2 to 8 and 11. The compositio n, microstructure, thermal properties, and mesomorphism of the homologues w ere determined using elemental analysis, H-1 NMR, FTIR, DSC, wide angle X-r ay diffraction, and polarizing optical microscopy with a heating stage. The influence of the length and the even/odd numbers of methylene units of the peripheral chains on the variants of mesomorphism and the stability of mes ophases, as well as on their transition temperatures, are discussed. The ho mologues with n = 8 and 11 were enantiotropic monomorphic, CrG (or CrH). Th e odd homologues showed monotropic trimorphism on cooling, while the even h omologues exhibited enantiotropic trimorphism. A pronounced even/odd effect on the melting temperatures was observed.