Structural Studies of 4‘-n-Alkoxy-3‘-nitrobiphenyl-4-carboxylic Acids by Infrared Spectroscopic Analysis

Abstract

Infrared (IR) spectra were measured for three 4‘-n-alkoxy-3‘-nitrobiphenyl-4-carboxylic acid homologues [ANBC-n, where the carbon number of the alkoxy group (n) is 14, 16, and 22] as a function of temperature. The phase sequences for ANBC-14, -16, and -22 are crystal (C)−smectic C (SC)−smectic A (SA)−“structured” liquid (I1)−isotropic liquid (I2), crystal 2 (C2)−crystal 1 (C1)−SC−cubic (D)−SA−I1−I2, and C−SC−D−I1−I2, respectively. The molar fraction of dimeric COOH groups was determined by using the absorbances of two bands at ∼1696 and ∼1734 cm-1, which are assigned to the dimer and monomer carbonyl stretching vibrations, respectively. In the crystalline phase all the COOH groups form hydrogen-bonded dimers, and the dissociation of the dimers into monomers occurs above the melting point. It is noted that about 85% of ANBC molecules are still in the dimer state in the D phase, and the D phase transforms into SA/I1 phase, when the fraction of dimeric COOH is ∼0.74 mol %, for both n = 16 and 22. The temperature dependence of the CH2 stretching bands for these two compounds suggests that the alkoxy chains are rather linear-shaped to hold some local order in the SC phase, and the conformational structure becomes liquidlike above the SC−D phase transition temperature. On the basis of the present IR results, we deduce a possible structure inside micelles in the D phase and the molecular state in the I1 phase.

Selective determination of glass transition temperature and vibrational properties at the chain end of polystyrene by Fourier transform infrared measurement in combination with deuterium-labeling

“…S2. This is similar to the feature of the symmetric stretching vibration mode of non-deuterated CH 2 which is rather insensitive to transitions [47].…”

Thermodynamic investigation of the thermotropic cubic mesogen, 1,2-bis(4- n -octyloxybenzoyl)hydrazine

“…on the basis of elastic properties. As the present mesogen However, dynamic viscoelastic properties [18], IR spectrohas no chirality and does not exhibit a nematic phase, scopy [19], and 14 N NMR [20] by Kutsumizu, Yano one need not take into account the twist and bend and their collaborators, and time-resolved di raction deformations. Only the splay distortion contributes to experiments by Levelut and Clerc [21] support the the curvature elasticity.…”

“…(3) through the carboxyl groups bring about the formation of dimers [19], while in the case of BABH there is a Another alternative to the cubic structure, which has strong tendency to the formation of hydrogen bonds been regarded as a good candidate for the structure in between the CO and NH groups, leading to lateral the cubic D phase, is the so-called jointed-rod model of interactions. Tardieu Phase transitions occurring within the solid state are mainly associated with successively increasing conw ( jointed-rod micelle)= Õ k24 (1 / R 2 ).…”

Synthesis and liquid crystalline properties of hydrazide derivatives: hydrogen bonding, molecular dipole, and smectic structures

“…the molecules are arranged within the lamellae in such a way that they are often randomly tilted at slight angles with respect to the layer normal, and the tilt angle enlarged with the increasing temperature (22); (ii) the chain conformation, the chain extended with decreasing distortion conformations on cooling (23)(24)(25). However, further experiments are still required to clarify the above.…”