Liquid crystalline polymers with biphenyl‐moieties as mesogenic group

Abstract

Based on a model consideration summarized in Fig. 1 systematic syntheses of liquid crystalline polymers with nematic, smectic and cholesteric phases have been realized'). The principal concept was to link conventional mesogenic groups to a polymer main chain via flexible spacer groups. A direct fixation of the mesogenic groups to the polymer main chain causes a coupling of the motions of the main chain and the mesogenic side chain. Thus-as stated by many publications in the field and summarized in recent reviews2)-the high mobility of chain segments in the liquid state of the polymer and its tendency towards a statistical chain conformation consequently prevents an anisotropic orientation of the mesogenic side chains above the glass transition temperature of the polymer. If the mesogenic groups are fixed via flexible spacer to the main chain the motions of the main chain and the side chains might be decoupled. In this case the mesogenic moieties are able to build up the orientational long range order although the motions of the main chain tend to prevent an anisotropic order. Following these model considerations, the liquid crystalline state of the polymers should be independent of the nature of the main chain and-as it is known for conventional low molecular weight liquid crystals-should be determined only by the nature of the mesogenic group. This so far could only be confirmed by using benzoic acid phenyl ester derivatives LINKAGE OF THE MESOGENIC SIDE CHAIN TO THE MAIN CHAIN P COUPLES MOTIONS

The Influence of Hydrogen Bonding on the Mesomorphic Properties of Side Chain Type Liquid Crystalline Polyurethanes with Rigid Moieties in the Polymer Backbone

“…This result was similar to the thermal dependence of the longer flexible spacer of conventional -SLCPs and low molecular liquid crystal. 5 Typical smectic and nematic phases were observed for the PU-MeO Azo.…”

Jacketed polymers: Controlled synthesis of mesogen‐jacketed polymers and block copolymers

“…Otherwise, flexible spacers are needed to decouple interactions between the main chain and the mesogenic side groups to achieve liquid crystallinity, which is the principle of traditional SCLCPs, proposed by Finkelmann and coworkers. 3,4 Just this tiny difference provides them with obviously different properties. SCLCPs resemble in many of their properties the analogous small LC molecules and are expected to show rapid response to outside stimulants, due to the ''decoupling'' effect.…”

Synthesis and characterization of liquid crystalline polysiloxanes containing benzyl ether mesogens

“…Since 1978 when Ringsdorf and Finkelmann have introduced the spacer concept (11,12), the synthesis of side-chain liquid crystalline polymers became an active area of polymer chemistry. This field has been recently reviewed (13,14).…”