Induced crystal G phase through intermolecular hydrogen bonding VII. Influence of non-covalent interactions on mesomorphism and crystallization kinetics

Citation
M. Srinivasulu et al., Induced crystal G phase through intermolecular hydrogen bonding VII. Influence of non-covalent interactions on mesomorphism and crystallization kinetics, LIQ CRYST, 28(9), 2001, pp. 1321-1329
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
LIQUID CRYSTALS
ISSN journal
0267-8292 → ACNP
Volume
28
Issue
9
Year of publication
2001
Pages
1321 - 1329
Database
ISI
SICI code
0267-8292(200109)28:9<1321:ICGPTI>2.0.ZU;2-U
Abstract
A series of intermolecular hydrogen bonding complexes, 2,2'-bipyridine : p- n-alkoxybenzoic acids (BP: nABA) was isolated from liquid crystalline p-n-a lkoxybenzoic acids (nABA) (where n represents alkoxy carbon numbers, 3 to 1 0 and 12) and a non-mesogen, 2,2'-bipyridine (BP). The thermal and phase be haviour of these complexes was studied by thermal microscopy and differenti al scanning calorimetry (DSC). These studies revealed the induction of tilt ed smectic F and crystal G phases. The structural elucidation pertaining to the formation of intermolecular hydrogen bonding was carried out by a deta iled IR spectral investigation. Comparative crystallization kinectic studie s using DSC, performed on two representative compounds, showed different fo rms of the crystallization process. The magnitudes of the Avrami exponent n suggests two different mechanisms operate for individual members leading t o sporadic three-dimensional growth. Nevertheless, an overall unique mechan ism is predicted to operate at each crystallization temperature investigate d, while the Avrami constant b shows a temperature dependence suggesting a strong influence of alkoxy terminal groups on the rates of nucleation.