Crystallization kinetics study on N-(p-n-alkyloxybenzylidene)-p-n-alkylanilines (nO.m compounds)

A comparative systematic kinetic study of crystallization among various smectogens of higher homologues of the benzylidene aniline nO.m series (9O.2, 13O.2, 14O.2, 15O.2, 16O.2, 2O.16, 11O.16, 16O.16 and 18O.16) has been carried out by thermal microscopy and differential scanning calorimetry (DSC). The DSC thermograms were run from crystallization temperature to the isotropic melt for different time interval. The liquid crystalline behaviour together with rate of crystallization of smectic ordering in newly synthesized nO.m compounds (16O.2, 2O.16, 11O.16, 16O.16, 18O.16) with respect to their lower homologues are discussed in relation to the kinetophase (which occurs prior to the crystallization), end chain lengths, the odd-even effect and chain length ratio. The molecular mechanism and dimensionality in the crystal growth were computed from the Avrami equation. The characteristic crystallization time (t*) at each crystallization temperature was deduced from the individual plots of log t vs. DeltaH. Further, a qualitative approach was made to the crystallization process in smectic layers.