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In this paper, two series of cholesteric liquid crystal polysiloxanes (PA and PB series) with selective reflection were synthesised. PA and PB series were both prepared by hydrosylation of monomer MA containing cholesterol, monomer MB containing D (+)-camphoric acid and 6-bromohexene (6-Br), besides PB series containing MC with cyano-group. The optical performance and thermal stability of PA and PB were observed, and the relationship between PB series and PA series was also studied. Tests such as POM, TGA, DSC and selective reflection showed that the polymers exhibited colourful Grandjean texture and excellent thermal stability. The Tg, Ti and the mesophase temperature for the PA series all tended to increase, and with the increase of steric hindrance of MB, the selective reflection may exhibit more difficulty. The PB series could dilute the steric hindrance of chiral monomers due to the introduction of cyano-group and the decrease content of MB, which not only guaranteed the polymer with wider mesophase temperature but also was conducive to appear the selective reflection and last longer, besides, with the temperature increased, the wavelength of the reflected light intended to blue shift compared to that of PA series with the same chiral contents. [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystals with selective reflection have important applications in the field of light control and optical thin films. In this study, a series of side-chain cholesteric liquid-crystal polymers (named as PPL series) was synthesised by a one-step hydrosilylation reaction among monomer LA containing cholesterol group, monomer LB containing D(+)-camphoric acid group and monomer LG containing cyano group. The chemical structures and the mesogenic properties of the monomers and polymers were determined by usual test methods. Testing results showed that PPL series polymers had excellent thermal stability and wide range of mesophases. As the content of monomer LB increased, PPL1-PPL6 could be observed colourful Grandjean textures and good selective reflection. The optical rotation experiment indicated that the rotation direction of the PPL series was consistent with that of the monomer LB, and the specific rotation was linearly related to the content of the monomer LB. [ABSTRACT FROM AUTHOR]

In this study, a series of cholesteric liquid crystal elastomers (ZSD series) was synthesised by hydrosilylation reaction among monomer ML1 containing cholesteryl group, monomer ML2 as the crosslinking agent, monomer ML3 containing D(+)-camphoric acid group. The chemical structures and mesogenic properties of monomers and elastomers were studied by conventional testing methods. By characterising the liquid crystal elastomers, it was found that they all showed colourful Grandjean texture, good elasticity and high thermal stability. For the ZSD series, the values of Tg first decreased and then increased and the values of Ti always decreased with the change of the content of chiral liquid crystal monomers, and all elastomers had the wide mesophase temperature ranges (ΔT). ZSD1-ZSD3 had selective reflection in the visible light region, while the observation for ZSD4-ZSD7 could only be observed under the appropriate external pressure. The effect of the novel chiral monomer (ML3) on the properties of elastomers had been investigated. [ABSTRACT FROM AUTHOR]

In this study, we designed, synthesised and characterised two series of cholesteric liquid crystal polymers, QP series and ZP series. With polymethylhydrosiloxane as the main chain, QP series were synthesised by copolymerisation between the monomer M1 containing a cholesteryl mesogenic unit and the monomer M2 with a hydroxyl. ZP series, meanwhile, were synthesised by esterification between QP series members and the monomer M3, a carboxylic acid with an azo mesogenic unit. We characterised chemical structures of all the monomers and polymers by FT-IR and 1H-NMR, which proved that the target monomers and polymers had been obtained. We observed dramatic colour changes after the introduction of monomer M3 and Grandjean textures from both QP series and ZP series using POM. In addition, strong selective reflection could be observed as well. Then, we characterised the thermal properties of polymers by DSC, TGA and XRD to explore their phase transition behaviours further. Their photoresponsive and photochromic properties were characterised by UV-Vis spectrum. [ABSTRACT FROM AUTHOR]

The article discusses a study which synthesized chiral side-chain liquid-crystalline polymers from smectic-nematic monomer and nonmesogenic chiral monomer. It notes that graft copolymerization was performed in this study, with polymethylhydrosiloxane serving as backbone. Results of the study showed that both smectic and nematic phases of the monomer occurred during the heating and cooling cycle. The study also observed nonmesogenic chiral moiety, as well as lower glass transition temperature.

A series of liquid crystalline homopolysiloxanes and copolysiloxanes were synthesized. The chemical structures of the monomers M 1 - M 7 were confirmed by FTIR and 1 H NMR spectroscopy. The structure-property relationships of the monomers and polymers are discussed; their phase behaviour and optical properties were investigated by differential scanning calorimetry, thermogravimetric analysis, and polarizing optical microscopy. All the monomers, except M 2 and M 7 showed smectic and nematic phases; the copolymers P 8 - P 15 displayed cholesteric phases. The homopolymers P 1 - P 7 exhibited smectic phases. The selective reflection of cholesteric monomers and copolymers shifted to longer wavelengths with increasing length of the rigid mesogenic core, with decreasing length of the flexible spacer, or with increasing content of nematic units. Experimental results demonstrated that a flexible polymer backbone, a rigid mesogenic core and a long flexible spacer tended to produce a lower glass transition temperature, higher thermal stability, and wider mesophase temperature range. [ABSTRACT FROM AUTHOR]

Abstract: Seven new cholesteric monomers (M-1−M-7) and the corresponding smectic comblike polymers containing cholesteryl groups (P-1−P-7) were synthesized. The chemical structures and purity were characterized by FT-IR, 1H NMR, and elemental analyses. The specific optical rotations were evaluated with a polarimeter. The mesomorphism was investigated by polarizing optical microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction. The specific optical rotation values of these monomers and polymers with the same numbers of phenyl ring and terminal groups were nearly equal, however, they decreased with increasing the aryl numbers in the mesogenic core. M-1−M-7 showed oily streak texture and focal conic texture, or fingerprint texture, or spiral texture of cholesteric phase. P-1−P-7 showed the smectic A phase. The melting, clearing, and glass transition temperatures increased, and the mesophase temperature ranges widened with increasing the aryl number in the mesogenic core. Surprisingly, although the molecular structures of M-6 and M-7 were similar to those of M-4, namely the mesogenic cores contained three phenyl rings, their phase behavior had a considerable difference, and T m and T i of M-6 and M-7 were less than those of M-4. In addition, M-6 and M-7 also showed an obvious glass transition. TGA showed that all the polymers had good thermal stabilities. [Copyright &y& Elsevier]

Abstract: The synthesis of five chiral liquid crystalline monomers (M 1–M 5), and their corresponding side-chain polymers (P 1–P 5) based on (S)-(+)-2-methyl-1-butanol derivatives is described. The chemical structures of the monomers were confirmed by FT-IR, 1H NMR, and elemental analyses. The structure-property relationships of the monomers and polymers obtained are discussed. The mesomorphic properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarizing optical microscopy (POM), and X-ray diffraction (XRD) measurements. All monomers showed a cholesteric phase. For M 2, M 3, and M 5, besides a cholesteric phase and a smectic A (SA) phase, M 2 also revealed an enantiotropic chiral smectic C phase and a monotropic smectic B (SB) phase, and M 3 also showed a SB phase. The polymers P 1–P 5 exhibited a SA phase, moreover, P 2, P 3 and P 5 also revealed a phase. The experimental results demonstrated that a flexible siloxane backbone and a long flexible spacer tended to exhibit a low glass transition temperature, high thermal stability, and wide mesophase temperature range. [Copyright &y& Elsevier]