Abstract
In this article, molecular dynamics and the cold crystallization kinetics of 4-(6-heptafluorobutanoiloxyhexyloxy)biphenyl-4′-carboxylan(S)-4-(1-methyloheptyloxycarbonyl) phenyl (abbreviated as 3F6Bi and/or 4H6) are presented. Rich polymorphism of the liquid-crystalline (SmA*, SmC*, SmC*A and SmI*A) phases and partially disordered crystal CrI and glassy GCrI were observed upon cooling. Both, molecular and collective relaxation processes were observed in the para-, ferro- and antiferro-electric liquid-crystalline phases over the frequency range of 3 × 10−2 to 3 × 106 Hz. An additional bias field in the dielectric experiments was used to identify individual processes. The high heating rates (5–10 K/min) phase sequence is the same as in case of the cooling experiment. On slow heating (0.5–2 K/min), cold crystallization of SmI*A to the more stable crystal CrII phase was observed in the dielectric and calorimetric experiments. The crystallization kinetics was analyzed using the Mo equation, which is a combination of the Avrami and Ozawa models. The activation energy of crystallization was calculated to be 138 and 99 kJ/mol using the Kissinger and Augis-Bennett models, respectively.
Highlights
Antiferroelectric liquid-crystalline substances having three phenyl rings in their molecular core are intensively studied as components of mixtures for generation liquid crystal displays [1,2,3]
In the dielectric measurements for the 3F6Bi dynamics was found in all liquid crystalline phases and in the partially disordered CrI and its glass
Its intensity (ε′′max ~ 600) is much larger than that registered for process in SmA* phase, and completely dominates the dielectric spectrum, one can suspect that other dynamic processes may be hidden in this region
Summary
Antiferroelectric liquid-crystalline substances having three phenyl rings in their molecular core are intensively studied as components of mixtures for generation liquid crystal displays [1,2,3]. These substances have usually rich phase polymorphism containing liquid crystalline, glassy, and metastable or stable crystalline phases [4,5]. The main aim of this work is to confirm the phase sequence for 3F6Bi, to investigate the influence of the heating rate on phase transitions, and to identify and describe the molecular dynamics of the liquidcrystalline phases using broadband dielectric spectroscopy, with bias electric field applied.
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