Induced smectic-G phase through intermolecular hydrogen bonding Part-V: Thermal and crystallisation kinetics studies

A novel series of liquid crystalline complexes formed through intermolecular hydrogen bonding between p-n-alkoxybenzoic acids (ABA) (where alkoxy = propoxy to decyloxy and dodecyloxy) and (2-(4-nonyloxybenzylidene amino)-5-chloro-pyridine (NACP) have been synthesised and their thermal and phase behaviour are studied by Thermal Microscopy (TM) and Differential Scanning Calorimetry (DSC). IR sspectral data confirm the formation of H-bonding between pyridine ring nitrogen and -COOH group of NACP and ABA respectively. Comparative thermal analyses of both free p-n-alkoxybenzoic acids and H-bonded complexes imply the inducement of smectic-G phase in all the complexes. A systematic kinetic study of crystallisation has also been performed on two representative compounds, NACP:NBA and NACP:DBA using DSC. The molecular mechanism and dimensionality in crystal growth among newly induced smectic-G phase are computed from the Avrami equation while the characteristic crystallisation time at each crystallisation temperature is deduced from the individual plots of log t vs. ΔH