Inter hydrogen bonded complexes of hexadecylaniline and alkoxy benzoic acids: a study of crystallization kinetics

Abstract

A systematic crystallization kinetic study of two smectogens of homologous series of the inter molecular hydrogen bonded between undecyl, dodecyl benzoic acids and hexadecylaniline complexes viz., 16A+11BA and 16A+12BA respectively has been carried out by thermal microscopy, differential scanning calorimetry (DSC) and dielectric studies. FTIR studies indicate the formation of hydrogen bond in these complexes. The crystallization kinetics was studied by two techniques viz., the traditional thermal analysis (DSC) and electrical studies in which capacitance and dielectric loss variation with temperature were recorded and analyzed. The DSC thermograms were run from crystallization temperature to the isotropic melt for different time intervals. The liquid crystalline behaviour together with the rate of crystallization of smectic ordering in newly synthesized inter hydrogen bonded complexes were discussed in relation to the kinetophase (which occurs prior to the crystallization). 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 and ∆H. Further, it was observed that the data obtained from DSC and dielectric studies were in good agreement with one another. For the first time in the history of crystallization studies, crystallization kinetics data is experimentally elicited from a novel dielectric technique.

Experimental evidence of an optical shutter in cholesteric phase of a double hydrogen bonded liquid crystal

“…The phase sequence of the levo tartaric acid and undecyloxy benzoic acid (LTA+11BA) hydrogen bonded complex in the cooling run can be shown as: The phase diagrams of pure p-n-alkoxy benzoic acids and the present homologous series (nBA+LTA) are constructed and reported [30] through optical polarizing microscopic studies by the phase transition temperatures observed in the cooling run of the mesogens of the present homologous series. The phase diagram of pure p-n-alkoxy benzoic acids is reported [24] to exhibit three phases namely, Nematic, smectic C* and smectic G*.…”

“…With our previous experience [23][24][25][26][27][28][29][30], in designing, synthesizing and characterizing various types of liquid crystals, a successful attempt has been made in characterizing a novel series of inter hydrogen bonded liquid crystal exhibiting optical shutter activity in cholesteric phase of LTA+11BA hydrogen bonded complex.…”

Dielectric Studies on Fe3O4Nanodopedp-n-Alkyloxybenzoic Acids

“…Low doping concentrations (<3% by weight) are usually preferred to get a more stable and for an even distribution in the LC, which will lower the interaction forces between particles [3,4]. --alkyloxybenzoic acids are extensively studied earlier and gained interesting results [5][6][7][8]. Various experimental techniques are being done on these alkyloxybenzoic acids on individual members and on mixed compounds [6,[8][9][10].…”

Dielectric and Optical Studies in Smectic C of A Novel Hydrogen Bonded Liquid Crystal Homologous Series

“…Many liquid crystal systems like molecular liquid crystals [22][23][24][25][26], polymer liquid crystals [27][28][29][30][31], ferroelectric liquid crystals [32,33], and even room temperature liquid crystals have been prepared [8]. Single bond [34][35][36], double bond [37][38][39][40], and even multiple bond [41,42] hydrogen-bonded liquid crystals are synthesized and reported.…”