Side‐Chain liquid‐crystalline polymers containing a siloxane spacer, 2. Effects of mesogenic groups on the thermal properties of side‐chain liquid‐crystalline polymers containing a disiloxane unit in the spacer

Abstract

A series of side-chain liquid-crystalline polymers was prepared containing disiloxane units in the spacer. The polymers consist of a polymethacrylate backbone and several kinds of mesogenic side groups. For the synthesis of the desired monomers, silanol compounds carrying a mesogenic group were prepared as the intermediates. The polymers were obtained by ordinary free-radical polymerization. As the mesogenic groups, linear-type p-or p'-substituted phenyl and biphenylyl benzoates, p-or m-substituted benzoyloxybiphenyl groups and laterally attached biphenylyl benzoate-type mesogens were chosen, and the structural effects on the thermal properties of the polymers were investigated. In the case of linear-type mesogens, only when triple-core mesogens were introduced a stable smectic mesophase was observed with a wide range of phase stability, while no mesophase was observed for the linear double-core and the laterally attached mesogens.On the other hand, a highly ordered smectic phase was observed for polymers having linear-type triple-core mesogens with p-alkoxy and m-cyano end groups. Furthermore, it was revealed that the introduction of a disiloxane unit in the spacer lowered the temperature range of the mesophase, in comparison with polymers having an alkylene spacer with the same backbone component and mesogens.

Side-Chain Liquid-Crystalline Polymers Containing the Siloxane Spacer V. Syntheses and Thermal Properties of Copolymethacrylates with Different Spacer Structures

“…3 The spacer length of the monomers 3a-3d is almost equal to that of the monomers 7a-7d, which is about 14A. However, it was found that, in the hydrosilylation of ethoxydimethylsilane with allyloxy compounds having the same laterally attached mesogens as 10a and 10b, side reactions mainly occurred to afford the desired product in very low yields, whereupon the silyl group was eliminated in the major products.…”

“…synthetic procedures of the monomers with a siloxane spacer, 7a-7d, 12a, and 12b, have been already described in our previous report. 3 Details of the preparations of the monomers, 3a-3d, including those of their intermediates are described below.…”

“…2 -5 The introduction of a flexible siloxane unit in the spacer lowered the temperature range of the mesophase of the polymers, in comparison with polymers having an alkylene spacer with the same backbone component and mesogens. 3 This would be due to the low rotational energy barrier of the siloxane linkage. However, only when triplecore mesogens were introduced, the stable smectic mesophase was observed with a wide range of phase stability, while no mesophase was observed for the linear double-core and laterally attached mesogens.…”

A new synthetic approach to side-chain liquid crystalline polyacrylates containing siloxane spacers and their thermal behaviours

“…action of sodium hydroxide, followed by the eseri® cation In the above reaction, 4-cyano-4¾ -hydroxybiphenyl of 6 a± 6 c with 4-cyanophenol or 4-cyano-4¾ -hydroxywas used instead of 4-cyanophenol to a ord M -7 ( yield: biphenyl to a ord the mesogenic ole® n compounds 71 per cent). moiety would prevent the liquid crystalline order of the mesogenic side chains [4].…”

“…The introduction of a siloxane bond in the spacer (siloxane spacer) a ected the phase transition behaviour and especially decreased the glass transition temperature (T g ) of the obtained polymers. As a result, the mesophase of SCLCPs containing a siloxane spacer appeared at the lower temperature range than that of SCLCPs containing an alkylene spacer with the same backbone components and mesogens [4,6 ]. In our Scheme In this paper, the convenient synthetic route of P-1± P-6 were carried out under an argon stream at the scanning rate of Ô 10ß C min Õ 1 , and those of P7 were monomers of SCLCPs containing siloxane spacers is presented.…”