Five simple benzenecarboxamide (BC) derivatives bearing
multiple −CONHC14H29 chainsN,N′-bis(tetradecyl)-1,4-benzenedicarboxamide
(2BC), N,N′,N″-tri(tetradecyl)-1,3,5-benzenetricarboxamide (3BC), N,N′,N″,N″-tetra(tetradecyl)-1,2,4,5-benzenetetracarboxamide
(4BC), N,N′,N″,N‴,N⁗-penta(tetradecyl)benzenepentacarboxamide
(5BC), and N,N′,N″,N‴,N⁗,N⁗′-hexa(tetradecyl)benzenehexacarboxamide
(6BC)were examined in terms of their molecular
assemblies in solution, organogels, liquid crystals, and solids as
well as their phase transition behavior and dielectric responses.
The molecular assemblies of compounds 3BC–6BC were dominated by the intermolecular N–H∼O=
hydrogen-bonding interactions along the π-stacking directions
and formed one-dimensional π-stacking nanofibers. The excellent
organogelation characteristics of compound 3BC were observed
in common organic solvents such as ethanol, acetonitrile, acetone,
and N,N-dimethylformamide, whereas
compounds 4BC and 6BC formed organogels
in hexane and/or toluene. Mechanical fraying of the three-dimensional
entangled nanofibers in the organogel state resulted in a two-dimensional
cobweb-like nanofiber network, where the typical height and width
of each nanofiber on the substrate surface were ca. 3.5 and 200 nm,
respectively. A single nanofiber was constructed by a π-stacking
column through intermolecular N–H∼O= hydrogen-bonding
interactions, of which the hexagonal arrangement resulted in ordered
hexagonal columnar (Colho) discotic liquid crystalline
phases for compounds 3BC–6BC. Both
of the intercolumnar and intracolumnar distances in the Colho phase were linearly increased according to the number of −CONHC14H29 chains. The temperature- and frequency-dependent
dielectric constants of compounds 2BC–6BC in cast-films revealed dielectric anomalies around the solid to
Colho phase transition temperatures due to thermally activated
molecular motion. Polarization–electric field (P–E) curves of compounds 2BC, 3BC, and 5BC in the mesophases showed hysteretic
behavior with ferroelectric ground states, whereas paraelectric behavior
with linear P–E dependence
was observed for compounds 4BC and 6BC.