123640-26-6Relevant articles and documents
Design of siloxane liquid crystals forming a de vries SmA* phase
Galli,Reihmann,Crudeli,Chiellini,Panarin, Yu,Vij,Blanc,Lorman,Olsson
, p. 245/2111-257/2123/ (2005)
We designed and synthesized new SmA* liquid crystals with different molecular architectures based on the chiral mesogen MR11, which was unsubstituted, or attached at one end and at both ends of a trisiloxane segment in the monosubstituted MSi3-MR11 and disubstituted DSi3-MR11 siloxanes, respectively. We studied the critical divergence of the magnetic susceptibility by measurements of the induced tilt angle θind at the SmA*-SmC* transition. While all three SmA* liquid crystals presented a de Vries character, this was quite distinctive for DSi3-MR11 for which the critical exponent γ = 1.87 was maximal. X-ray diffraction experiments confirmed that the SmA*-SmC* transition occurred with essentially no layer shrinkage.
Synthesis and characterization of ferroelectric liquid crystalline siloxanes containing 4-hydroxyphenyl(2S,3S)-2-chloro-3-methylvalerate
Lin, Chih-Hung
experimental part, p. 33 - 42 (2012/05/04)
New series of organosiloxane ferroelectric liquid crystalline materials have been synthesized, and their mesomorphic and physical properties have been characterized. These new series contain bis-siloxane or tris-siloxane unit attached to the flexible alkyl chain end of (2S,3S)-2-chloro-3-methylvalerate. The siloxane molecule induction is helpful to the chiral smectic C (S C) formation and chiral SC* stabilization, and it simultaneously causes the liquid crystal temperature range of chiral S C* to be broader. The siloxane member is helpful in reducing the smectic C (SC) transation shift temperature, and the molecule containing tris-siloxane units shows better effect than the bis-siloxane one. The synthesis and characterization of the new FLCs materials which exhibit SC* phase at room temperature and higher spontaneous polarization are presented.
Organic-inorganic hybrid liquid crystals derived from octameric silsesquioxanes. Effect of the peripheral groups in mesogens on the formation of liquid crystals
Wang, Xiaobai,Cho, Ching Mui,Say, Wan Yong,Tan, Angeline Yan Xuan,He, Chaobin,Chan, Hardy Sze On,Xu, Jianwei
experimental part, p. 5248 - 5257 (2011/11/29)
A series of octameric silsesquioxane-based organic-inorganic hybrid compounds 7a-h was synthesised by reacting octakis(dimethylsiloxy)silsesquioxane with 4′-(undec-10-enyloxy)biphenyl-4-yl mono-, di-, or trialkoxybenzoate via platinum-catalysed hydrosilylation reaction. The chemical structures of 7a-h were characterised by 1H, 13C, and 29Si nuclear magnetic resonance spectroscopy, mass spectroscopy and elemental analysis. Liquid crystallinity of 7a-h was investigated by differential scanning calorimetry (DSC) and polarised optical microscopy (POM). Temperature-dependent X-ray diffraction was used to verify liquid crystal phases, revealing that 7a-d assembled to smectic C and smectic A phases. The effects of the number and length of peripheral flexible alkoxy groups in 7a-h on the formation of liquid crystals were studied using DSC and POM, which revealed that 7a-d bore one alkoxy terminal group in each mesogen exhibited a mesophase, 7e-f and 7g-h bore two and three flexible alkoxy terminal groups in each mesogen, respectively, and did not show mesomorphic behaviour. The concept of "flexible group density" (FGD), which was defined as the number of the CH2 groups per unit volume in the periphery of the POSS molecule, was introduced to interpret the formation of liquid crystals. The results revealed that the POSS molecules with di- and tri-substituted mesogens exhibited much larger FGD than those with mono-substituted mesogens, hence the absence of mesophases for 7e-f and 7g-h. This study provides a useful archetype to predict the formation of liquid crystals when designing and synthesising liquid crystalline materials, particularly star-like or dendrimer-like molecular materials.
