Influence of carbon chain length on physical properties of 3FmHPhF homologues

On relaxation and vibrational dynamics in the thermodynamic states of a chiral smectogenic glass-former

“…The coexistence of both processes, P H and P L in the SmC Ã A phase, was also observed in other compounds with a similar molecular structure. 30,43,50,51 The third process (interpreted as the a-process) is recorded in the high frequency range at only a few temperatures upon slow cooling, i.e., close to melt crystallization of the sample. As described earlier, this mode is typical for materials undergoing vitrification.…”

“…This compound belongs to a family of 3FmX 1 PhX 2 r compounds (where '3F' is the C 3 F 7 -group, 'm' is the number of methylene groups in the non-chiral terminal chain, m = 2-7, 'X 1 ' and 'X 2 ' are hydrogen H or fluorine F atoms in the phenyl ring, and 'r' is the length of alkyl chain connected with the asymmetric carbon atom, r = 4-9), which have been extensively investigated. [2][3][4][5][6][7][8] The characteristic features of these compounds are the presence of the SmC Ã A phase at the broad temperature range and the value of the tilt angle of approx. 451, which leads to the optical uniaxiality, and consequently, much better quality of the dark state compared to the SmC Ã A phase with the smaller tilt angle.…”

Molecular Dynamics and Kinetics of Isothermal Cold Crystallization in the Chiral Smectogenic 3F7FPhH6 Glassformer

“…The hindrance of cold crystallization by the presence of different crystal phases seems even more probable when one looks at the behavior of the 3F5HPhF6 compound [14] from the same homologous series as 3F7HPhF6. The DSC results for these homologues [12,14] show than for 3F5HPhF6, cold crystallization occurs much slower than for 3F7HPhF6 and, most importantly, in 3F5HPhF6 there are two crystal phases confirmed by the XRD measurement [14].…”

“…The hindrance of cold crystallization by the presence of different crystal phases seems even more probable when one looks at the behavior of the 3F5HPhF6 compound [14] from the same homologous series as 3F7HPhF6. The DSC results for these homologues [12,14] show than for 3F5HPhF6, cold crystallization occurs much slower than for 3F7HPhF6 and, most importantly, in 3F5HPhF6 there are two crystal phases confirmed by the XRD measurement [14]. Although the detailed investigations of the cold crystallization kinetics for 3F5HPhF6 have not yet been published, there is a high possibility that the slowing down of crystallization is connected with a polymorphism of the crystal phases, as is suspected for 3F7HPhH6.…”

“…Moreover, the tilt angle in these compounds often approaches 45 • , which leads to the optical uniaxiality and, consequently, far better quality of the dark state compared to the SmC * A phase with the smaller tilt angle [10,11]. For a few of the mentioned fluorinated smectogens, the glass transition of the SmC * A phase was reported, even for slow cooling (1 K/min or at an even lower rate, enough to avoid crystallization) [12][13][14][15][16][17][18]. It allows for the obtainment of glass with anisotropic properties, whose practical application was already proposed both for smectic and nematic glassformers [19][20][21][22][23].…”