The phase transition behaviour and electro-rheological effect of liquid crystalline siloxane dimers

Abstract

Symmetrical liquid crystalline dimers have been synthesised, composed of rod-like mesogenic units with polar groups and a siloxane core of varying length in the central region. All the dimers containing siloxane units have been shown to exhibit a smectic A phase, confirmed by polarising optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Rheological properties under an applied electric field were investigated by rotational rheometer. The influence of the siloxane core length on rheological properties has been investigated, and in addition the behaviour of the liquid crystalline dimers in the smectic A phase under an applied electric field has been observed by POM.

4-[2-(Trimethylsilyl)ethynyl]benzoates: Synthesis and evaluation for mesomorphic properties of some novel calamitic molecules

“…The siloxane based liquid crystal materials exhibited the attractive properties as a result of the flexibility of the siloxane swallow tail backbone. The flexibility of the siloxane also led to low viscosities and low glass transition temperatures [11].…”

Synthesis of Some Novel Aromatic Alkynyl Silanes: Mesomorphic Characterization of Ethynyl-Substituted Rod-Shaped Molecules

“…All chemical structures are shown in Table 1 [20]. To a refluxing suspension of iodophenol (2.5 g, 1.0 mmol), copper acetate monohydrate (1.35 g, 1.07 mmol), and palladium chloride (1.8 g, 1.07 mmol) in triethylamine (10 mL) in an inert atmosphere was added dropwise trimethylsilylacetylene (1.36 g, 1.20 mmol) over 30 min.…”

“…All benzoic acid derivatives were prepared according to the reported literature procedures [6,29,30]. 1-(4 ;-Hydroxyphenyl)-2-trimethylsilylacetylene (2) [20] was used to prepare the compounds 3a-j. 1-(4 ;-n-Pentyloxyphenyl)-2-trimethylsilylacetylene (5) was used for the preparation of compounds 7 and 8, respectively, according to Scheme 1.…”

“…The reported synthetic strategies used for the preparation of trimethylsilylethynyl containing biological molecules and rod, disc, and banana-shaped compounds suffer from certain synthetic procedures [17][18][19]. Recently, Hanasaki et al and Liao et al reported polar groups containing symmetric and achiral swallow tail-derived siloxane dimers [20,21].…”

Electrorheological Properties of Liquid Crystalline Gold Nanoparticles in a Nematic Solvent

“…To date, there have been many experimental and theoretical studies of both their fundamental and their practical applications [1][2][3][4][5][6][7][8][9][10] since the first investigation of the phenomenon by Winslow [11]. ER fluids are mainly divided into two types on the basis of the component of the fluids and the mechanism of the effect.…”