Isothermal and Non-isothermal
Crystallization in Liquid Crystals as Seen
by Broadband Dielectric Spectroscopy
and Differential Scanning Calorimetry
Małgorzata Jasiurkowska-Delaporte
Abstract Being composed of shape-anisotropic molecules, liquid crystals (LCs)
differ from simple liquids in that they demonstrate a tendency to orientate in
specific directions and form various mesophases. Upon cooling, these partially
ordered liquid crystalline phases can either vitrify or crystallize. Upon heating
from a glassy state, LCs, like other low molecular weight systems and polymers,
have been found to undergo so-called cold crystallization. This chapter discusses
the findings of broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) studies of the isothermal and non-isothermal crystallization
kinetics of the supercooled nematic (N) and chiral nematic (N*) states of, respectively,
2,7-bis(4-pentylphenyl)-9,9-diethyl-9H-fluorene (5P-EtFLEt-P5) and S,S-2,7-bis(4pentylphenyl)-9,9-dimethylbutyl-9H-fluorene (5P-Am*FLAm*P5). The isothermal
melt and cold crystallization processes at selected temperatures T c above the glass
transition temperature T g (1.07T g ≤ T c ≤ 1.17T g ) are compared in 5P-EtFLEtP5. It was found that 5P-EtFLEt-P5 and 5P-Am*FLAm*P5 display different types
of non-isothermal cold crystallization. Finally, the paper discusses the crystallization behavior occurring in the well-ordered smectic B phase (SmB) of 4-nbutyloxybenzylidene-4
-n
-octylaniline (BBOA) under various thermal conditions.
The DSC analysis revealed two different crystallization mechanisms for fast and
slow cooling.
Keywords Liquid crystals · Molecular dynamics · Non-isothermal
crystallization · Isothermal crystallization · Broadband dielectric spectroscopy ·
Differential scanning calorimetry
M. Jasiurkowska-Delaporte (B)
Institute of Nuclear Physics Polish Academy of Sciences, 31342 Krakow, Poland
e-mail: Malgorzata.Jasiurkowska-Delaporte@ifj.edu.pl
© Springer Nature Switzerland AG 2020
T. A. Ezquerra and A. Nogales (eds.), Crystallization as Studied
by Broadband Dielectric Spectroscopy, Advances in Dielectrics,
https://doi.org/10.1007/978-3-030-56186-4_5
119
Crystallization in Liquid Crystals as Seen
by Broadband Dielectric Spectroscopy
and Differential Scanning Calorimetry
Małgorzata Jasiurkowska-Delaporte
Abstract Being composed of shape-anisotropic molecules, liquid crystals (LCs)
differ from simple liquids in that they demonstrate a tendency to orientate in
specific directions and form various mesophases. Upon cooling, these partially
ordered liquid crystalline phases can either vitrify or crystallize. Upon heating
from a glassy state, LCs, like other low molecular weight systems and polymers,
have been found to undergo so-called cold crystallization. This chapter discusses
the findings of broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) studies of the isothermal and non-isothermal crystallization
kinetics of the supercooled nematic (N) and chiral nematic (N*) states of, respectively,
2,7-bis(4-pentylphenyl)-9,9-diethyl-9H-fluorene (5P-EtFLEt-P5) and S,S-2,7-bis(4pentylphenyl)-9,9-dimethylbutyl-9H-fluorene (5P-Am*FLAm*P5). The isothermal
melt and cold crystallization processes at selected temperatures T c above the glass
transition temperature T g (1.07T g ≤ T c ≤ 1.17T g ) are compared in 5P-EtFLEtP5. It was found that 5P-EtFLEt-P5 and 5P-Am*FLAm*P5 display different types
of non-isothermal cold crystallization. Finally, the paper discusses the crystallization behavior occurring in the well-ordered smectic B phase (SmB) of 4-nbutyloxybenzylidene-4
-n
-octylaniline (BBOA) under various thermal conditions.
The DSC analysis revealed two different crystallization mechanisms for fast and
slow cooling.
Keywords Liquid crystals · Molecular dynamics · Non-isothermal
crystallization · Isothermal crystallization · Broadband dielectric spectroscopy ·
Differential scanning calorimetry
M. Jasiurkowska-Delaporte (B)
Institute of Nuclear Physics Polish Academy of Sciences, 31342 Krakow, Poland
e-mail: Malgorzata.Jasiurkowska-Delaporte@ifj.edu.pl
© Springer Nature Switzerland AG 2020
T. A. Ezquerra and A. Nogales (eds.), Crystallization as Studied
by Broadband Dielectric Spectroscopy, Advances in Dielectrics,
https://doi.org/10.1007/978-3-030-56186-4_5
119