134
M. Jasiurkowska-Delaporte
Fig. 9 a A scheme presenting thermal treatment protocol applied to study the cold crystallization process of the Cr2 phase in 5P-Am*FLAm*P5. b Dielectric loss spectra in the course of
isothermal crystallization of the Cr2 phase at 273 K. c Normalized dielectric strength ε N (t) as a
function of time during isothermal crystallization at selected temperatures, as indicated. d Avrami
plot: ln[−ln(1−ε N )] versus ln(t) for the data presented in panel b. Adapted from [30] with kind
permission of The European Physical Journal (EPJ)
rates was quantified as the slope of the linear dependence of ln(τ cryst ) against ln(τ α )
(Fig. 10b). The value of ζ ≈ 0.51 obtained for 5P-Am*FLAm*P5 is slightly higher
than that found for 5P-EtFLEt-P5 (ζ ≈ 0.44) at the temperature range T c < 1.1T g . In
both cases, the estimation agrees well with the value predicted based on the fragility
index m f . At T > 277, a fall in the coupling coefficient value was observed (ζ ≈ 0.2);
this hints at the role of the kinetic factor in the crystallization in the nematic phase of
5P-EtFLEt-P5 being reduced in favor of thermodynamic driving force mechanism.
The values of the crystallization activation energy (E c ) for the investigated LCs
were determined by fitting the Arrhenius function to the temperature dependence
of ln(τ cryst ) (Fig. 11a). For 5P-EtFLEt-P5, the energy of crystallization in the N
phase significantly increases from E c ≈ 32 kJ/mol to E c ≈ 100 kJ/mol below 277 K,
which suggests a change in the crystallization mechanism. In the case of isothermal
crystallization in N* of 5P-Am*FLAm*P5 taking place above the glass transition
temperature, E c was found to be 114 ± 6 kJ/mol.
The Avrami parameter n A was found to fall from 4 to 2.8 as the crystallization
temperatures increased, indicating that the N* phase of 5P-Am*FLAm*P5 underwent spherical growth in three dimensions. More pronounced variation of n A values
was revealed for 5P-EtFLEt-P5 (n A ≈ 5 at 271 K), indicating the formation of bundlelike or sheaflike crystallites; the value of n≈3 suggests the presence of spherically
M. Jasiurkowska-Delaporte
Fig. 9 a A scheme presenting thermal treatment protocol applied to study the cold crystallization process of the Cr2 phase in 5P-Am*FLAm*P5. b Dielectric loss spectra in the course of
isothermal crystallization of the Cr2 phase at 273 K. c Normalized dielectric strength ε N (t) as a
function of time during isothermal crystallization at selected temperatures, as indicated. d Avrami
plot: ln[−ln(1−ε N )] versus ln(t) for the data presented in panel b. Adapted from [30] with kind
permission of The European Physical Journal (EPJ)
rates was quantified as the slope of the linear dependence of ln(τ cryst ) against ln(τ α )
(Fig. 10b). The value of ζ ≈ 0.51 obtained for 5P-Am*FLAm*P5 is slightly higher
than that found for 5P-EtFLEt-P5 (ζ ≈ 0.44) at the temperature range T c < 1.1T g . In
both cases, the estimation agrees well with the value predicted based on the fragility
index m f . At T > 277, a fall in the coupling coefficient value was observed (ζ ≈ 0.2);
this hints at the role of the kinetic factor in the crystallization in the nematic phase of
5P-EtFLEt-P5 being reduced in favor of thermodynamic driving force mechanism.
The values of the crystallization activation energy (E c ) for the investigated LCs
were determined by fitting the Arrhenius function to the temperature dependence
of ln(τ cryst ) (Fig. 11a). For 5P-EtFLEt-P5, the energy of crystallization in the N
phase significantly increases from E c ≈ 32 kJ/mol to E c ≈ 100 kJ/mol below 277 K,
which suggests a change in the crystallization mechanism. In the case of isothermal
crystallization in N* of 5P-Am*FLAm*P5 taking place above the glass transition
temperature, E c was found to be 114 ± 6 kJ/mol.
The Avrami parameter n A was found to fall from 4 to 2.8 as the crystallization
temperatures increased, indicating that the N* phase of 5P-Am*FLAm*P5 underwent spherical growth in three dimensions. More pronounced variation of n A values
was revealed for 5P-EtFLEt-P5 (n A ≈ 5 at 271 K), indicating the formation of bundlelike or sheaflike crystallites; the value of n≈3 suggests the presence of spherically