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.
Approximately two-thirds of patients with radiologically resectable pancreatic cancer had MVI and were considered to have potentially systemic disease. This study identified MVI as one of the significant factors for a poor prognosis and a valuable complement of tumor-node-metastasis staging.
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