Liquid crystalline polysiloxanes with thioether type spacers and chiral biphenyl mesogens

Abstract

SUMMARY: Two chiral liquid-crystalline polymers with polysiloxane main chains, thioether type spacers, and biphenyl derivatives bearing one or two chiral atoms as mesogens were prepared by polyhydrosilylation of polymethylhydrogenosiloxane with a-thioolefins carrying biphenyl-based mesogens in the presence of hexachloroplatinic acid. The polymers exhibit two mesophases as a function of temperature. The nature of the first mesophase depends upon the nature of the chiral substituent of the biphenyl, but the second one is always of the SmC * type and covers a large range of temperature.

Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

“…They are similar to those which already were obtained with other polysiloxanes previously carried out at the laboratory. [12,13] …”

“…The dielectric spectra of the liquidcrystalline cyanobiphenyl polysiloxanes VII and VIII which present same length spacers (Figure 8 and 9), are similar to the spectra of the model polysiloxanes already prepared at the laboratory. [12,13,21] Three relaxations could be identified: i) a g-relaxation appears at low temperatures. It is due to the internal movements of the alcoxy functions connected to the spacer and the mesogen group.…”

“…[11] The first ''cyanobiphenyl'' and ''nitrobiphenyl'' liquid-crystalline polysiloxanes with thioether spacers (n ¼ 6, 8, 10 and m ¼ 2; see Figure 1) have been carried out in our laboratory. [12,13] This work enabled to develop their synthesis protocol and to prove that the thioether spacer removes the crystallization phenomenon. This concept is easily to be set up compared to the other ones.…”

“…They have been obtained by lengthening the spacer and by modifying the position of sulfur in the polymethylenic chain (m ¼ 2 and 3). This study is based on results previously obtained in our laboratory [12,13] with the goal to specify the flexibility of the thioether spacer. It will also make it possible to precise the limits of its efficiency.…”

Synthesis and characterization of polyepichlorohydrin-based copolymers with biphenyl groups attached thioether unit

“…The thioether unit containing in spacer or main-chain backbone can enhance the flexibility of the spacer or main chain, remove the crystallization phenomenon and obtain larger ranges of mesophases of copolymers owing to the longer length and weaker bond strength of C-S bond than those of C-C bond and C-O bond [7][8][9][10][11] . However, the influence of sulfur atom in substitution group on the thermal properties had not been reported.…”