Abstract
A series of new organosiloxane ferroelectric liquid crystalline (FLC) materials have been synthesized, and their mesomorphic and physical properties have been characterized. Four new disiloxanes and trisiloxanes, containing biphenyl 4-hydroxybenzoate and phenyl 4-hydroxybiphenylcarboxylate as mesogenic units and eleven methylene unit as spacers and (2S,3S)-2-chloro-3-methylvalerate unit as chiral end groups. The molecule, using three phenyl ring as a mesogenic unit, formulates much wider liquid crystalline phase temperature ranges than that of a two phenyl ring unit. The phenyl arrangement differences of mesogenic unit result in the greater differences of the liquid crystal phase formation. The siloxane molecule induction is helpful to the more regular smectic phase formation and smectic phase stabilization, such as chiral SC (SC*) and SB phases. The siloxane molecule is helpful to reduce the phase transition temperature and broaden the liquid crystal temperature range of the SC* phase and, simultaneously, it will not induce chain crystallization phenomenon and dilute the Ps value. The synthesis and characterization of the new FLCs materials, which exhibit a room temperature SC* phase and higher spontaneous polarization are presented.
Highlights
Organosiloxane low molar mass (LMM) liquid crystals have attracted considerable interest because their electro-optic properties are similar to those of classical LMM liquid crystals, demonstrating fast switching times in the nematic [1], SA [2], and SC* phases [3,4,5]
This study intends to explore two influences: one is the influence of the liquid crystal compound with siloxane end-tail, and the other is the influence from different rigid core arrangements in the mesogenic unit that change the thermal properties of liquid crystalline and liquid crystal mesophase
Schemes 1,2 illustrate the synthesis procedure of the reaction intermediates and the liquid crystal compounds, and all the products of these two series were examined by the nuclear magnetic resonance spectrometer to verify the correction of the molecular structure
Summary
Organosiloxane low molar mass (LMM) liquid crystals have attracted considerable interest because their electro-optic properties are similar to those of classical LMM liquid crystals, demonstrating fast switching times in the nematic [1], SA [2], and SC* phases [3,4,5]. Materials, exhibiting a room temperature SC* phase and low melting temperatures are of great interest to researchers in the electro-optic field [6,7,8,9,10,11]. We designed and prepared two new series of molecules, which contains two chiral centers and dimethylsiloxyl (or trimethylsiloxyl) substituent groups linked through flexible hydrocarbon chains. The difference between these two series is the sequence of the phenyl rings’. The substitution of methylsiloxyl groups was expected to enhance the thermal stability and Ps value of the FLC materials [18,19,20,21]
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