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.
Mesomorphic properties of (S)-MHPSBOn series
Abstract This article reports new results on synthesis and mesomorphic properties of the homologous series of ( S )-1-methylheptyl-4-(4′-alkyloxybiphenylthiocarboxy)-benzoates, referred to as ( S )-MHPSBO n , where n varies from 7 to 10 and denotes the number of carbon atoms in the alkyl chain. These compounds are sulphur analogous to a liquid crystal known as MHPOBC, where the central ester bridge was replaced with the –COS– connecting group. The ( S )-MHPSBO n homologous series possesses enantiotropic SmA*, SmC*, Sm C A * and monotropic SmI* phases for n  = 7–10. The ( S )-MHPSBO7 compound has also smectic chiral subphases: Sm C α * and Sm C γ * . Their mesomorphic properties were investigated by means of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), transmittance light intensity (TLI), X-ray diffraction and electro-optic (EO) measurements.
Interaction of Diclofop-Methyl and MCPA on Wild Oats (Avena fatua)
Diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate} loses part of its activity on wild oats (Avena fatua L.) when it is applied in combination with ester or amine formulations of MCPA {[4-chloro-o-tolyl)oxy] acetic acid.} Uptake of diclofop-methyl is reduced in the presence of commercial formulations of MCPA, particularly amine formulations, which are only partly compatible with the diclofop-methyl formulation. With added MCPA, regardless of formulation, hydrolysis of diclofop-methyl to the acid diclofop is slowed down, both in intact wild oat plants and in a crude leaf extract. At the same time, conversion of any acid formed to inactive conjugates is accelerated in the presence of MCPA. It is concluded that the loss of activity of diclofop-methyl by MCPA can be accounted for by the effects of MCPA on uptake and metabolic conversion of diclofop-methyl.