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

Abstract

Three new cyanobiphenyl polysiloxanes presenting long thioether spacers have been carried out. This type of spacer leads to very stable liquid‐crystalline polymers at room temperature and remove the crystallinity phenomenon. Dielectric analysis results show that the thioether spacer brings much more molecular flexibility to the system.Example of an “interdigitated” structure observed by X‐ray analysis.magnified imageExample of an “interdigitated” structure observed by X‐ray analysis.

Alditol thiacrowns via a ring-closing metathesis of carbohydrate-derived α,ω-dithioallylethers

“…The observed 1 H-NMR coupling constants on the contrary indicates an alternative, wherein the planar conformation in 12b has rotated not only about its C2-C3 bond, but also about its C3-C4 bond to leading to an unusually bent anti-anti-anti conformer 12b. Such a conformation has previously been reported for derivatives such as the per-Oacetylated 1,6-dithioether-D-glucitols analogs 28, 29 and 30 24 (entries [6][7][8], which are all characterized by a relatively large value of 5.2 Hz for their J 34 coupling constant. It is interesting to note that in analogs in which there is a single thioether group, for example at only C1 in derivative 27 24 (Table 2, entry 5), the value for J 34 remains small, indicative of syn-related H-3/H-4-methines.…”

“…Thioethers have attracted much interest in the last two decades, as revealed by publications dealing with methods for their synthesis 1 on the one hand and their exploitation in catalysis, 2 in ion-sensing, 3 the environment, 4 as amphiphiles, 5 as liquid crystals, 6 in cancer chemoprotection, 7 as enzyme inhibitors, 8 and as intermediates in organic synthesis, on the other. 9 Two classes of thioether deserve special mention in the context of the present article: linear thioethers 10 and also their cyclic counterparts.…”

Novel triethylamine catalyzed S → O acetyl migration reaction to generate candidate thiols for construction of topological and functional sulfur-containing polymers

“…Functional polymer materials like oxidation-responsive bio(nano)materials, 1 polysulde elastomers, 2 fast curing agent for epoxy resins, 3 degradable materials, 4 high refractive index lm, 5 and liquid crystal polymers 6 have been developed. Their related chemistry, especially thiol-click chemistry, including thiol-Michael addition, thiol-ene, thiol-yne, thiol-isocyanate, thiol-isothiocyanate and thiol-halogen reactions, has attracted immense scientic interest.…”

Synthesis and thermal properties of polythioether‐based liquid‐crystalline polymers containing azobenzene in the side chain

“…A thioether structure can contribute to the formation of a thermotropic liquid‐crystalline phase and increase the stability. When inserted into a carbon‐based main chain or spacer, the thioether unit can enhance the flexibility of the backbone or spacer and remove the crystallization phenomenon of copolymers owing to the CS bond of longer length and weaker bond strength, therefore resulting in broader mesophase ranges 11–14. In addition, due to the chelating properties of sulfur atoms, there is some capacity for adsorbing heavy and noble metal ions such as Au 3+ , Ag + , Cu 2+ , etc., especially the selective adsorption towards certain metal ions after quenching 15–17.…”