Dynamics and the mesomorphic properties of a novel antiferroelectric liquid crystalline thiobenzoate MHPSBO10: thermal, optical and dielectric spectroscopy study.
The complementary studies of the mesomorphic properties of a novel antiferroelectric liquid crystal (AFLC) (S)-2-octile 4-S-(4'decyloxybiphenyl-4-tiocarboxy)benzoate, known under MHPSBO10 acronym have been undertaken. The polymorphism has been complementary studied in details by Differential Scanning Calorimetry (DSC), Transmitted Light Intensity (TLI) and Polarization Microscopy (POM). The switching characteristics along with multiple macroscopic parameters describing the mesomorphic properties were determined by using electro-optic measurements, both upon cooling and heating. Frequency domain dielectric spectroscopy (DS), covering a wide frequency range, has been applied to characterize the molecular motions. Several collective modes, including the low frequency processes in the condensed hexatic phase were detected, analyzed in details and followed with the temperature. The presented studies deliver a wide report of the phase transitions, molecular dynamics and the macroscopic properties of the novel antiferroelectric thiobenzoate.
Phase transitions of new antiferroelectric thiobenzoate
This article reports on the phase sequences in a new chiral liquid crystalline compound, a member of the thioester series, (S)-(+)-4-[(4-{[1-methyl]heptylcarboxyl}phenyl)-carbonylthio]phenyl-4′-decyloxy-1-benzencarboxylate, referred to as 10.OPOSMH, which has been recently synthesized. 10.OPOSMH exhibits ferro- and antiferroelectric behaviour. This compound contains three benzene rings connected with the ester and thioester central groups. The 10.OPOSMH molecule is terminated with the achiral n-decyloxy and chiral (S)-(+)-1-methylheptyl carboxylate terminal chains, where the chiral group is in para position with respect to the thioester group. This mesogen assumes the existence of antiferroelectric smectic C ( ) and ferroelectric smectic C ( ) phases and also the smectic chiral subphases: , and , both on heating and cooling. †This article is dedicated to Prof. Dr Jerzy A. Janik on his 80th birthday.
The Polymorphism Of 4-N-Pentylphenyl-4″-N-Butyloxythio-Benzoate, (4OS5) In The Crystalline State
The title compound, 4-n-pentylphenyl-4′-n-butyloxythiobenzoate (4OS5), C 22 H 28 O 2 S, crystallized from methanol and hexane, reveals two polymorph forms in the crystalline state. The crystal and molecular structures of both polymorphs 4OS5-M (from methanol) and 4OS5-H (from hexane) are reported. 4OS5-M crystallizes in the monoclinic system, space group C2/c, with cell constants a=39.43(2), b=5.426(3), c=20.392(5) Å, β=105.15(3)°, V=4211(3) Å 3 , and Z=8. The crystal data of 4OS5-H are: monoclinic system, space group P2 1 /c, a=13.512(6), b=8.427(2), c=18.630(5) Å, β=96.98(3)°, V=2106(1) Å 3 , Z=4. The structures were solved by direct methods and refined to the final R=0.0569 and 0.0982 for 3242 and 1498 observed reflections for 4OS5-M and 4OS5-H, respectively. The molecules of both polymorphs 4OS5 differ only in the conformation of butyloxy chain: all trans in 4OS5-M and trans-gauche-trans in 4OS5-H. Theoretical calculations made by semiempirical AM1-MNDO method showed that both conformations are stable and almost equienergetical. The unit-cell packing in crystals of 4OS5 is characterized by the occurrence of the molecular layers, additionally stabilized by the net of weak C-H…O intermolecular hydrogen bonds in 4OS5-M.