Structural effects on mesomorphic properties in isomeric liquid crystalline polyesters

Two series (I-m and II-m) of isomeric liquid crystalline polyesters containing two mesogenic p-oxybenzoyl dyads separated by a couple of spacers derived from triethylene glycol and a polymethylene segment of variable length have been prepared and characterized for their mesomorphic properties. In both polymer series the parity and length of the polymethylene spacer play an integral role in determining the onset and stability of the liquid crystalline state. The thermodynamic data indicate that even members possess a great propensity to participate in the ordering process in the nematic state. Low mesogen order and depressed transition temperatures are observed for odd members of series II-m while no liquid crystalline behavior is detected for odd members of series I-m.