Laterally-attached side chain liquid crystal polymers

Zhou QF, Li HM, Feng XD (1988) Synthesis of a new class of side chain liquid crystal polymers— polymers with mesogens laterally attached via shtut linkages to polymer backbones. Mol Cryst Liq Cryst 155 73-82... 

Rigid polymers are not the only class of polymers which can show liquid crystal phases. These phases are also found in the melts of polymers in which mesogenic units are incorporated in the backbone (main chain polymers) or attached as pendants to the backbone (side chain polymers). These liquid crystalline polymers will be discussed in later sections. 

F. Hessel and H. Finkelmann, A new class of liquid crystal side chain polymers. Meshogenic groups laterally attached to the polymer backbone. Polym. Bull. 14, 375-378 (1985). 

Weissflog and Demus [8] succeeded in synthesizing a new type of liquid crystalline material, in which the rotation of the molecules about their long molecular axis was hindered by the introduction of laterally attached substituents. However, experiments conducted on these liquid crystals proved the existence of conventional uniaxial nematic phases only. Beyond that, a further restriction of the rotation of the mesogens by connecting them via terminal spacers to a polymer backbone end-on polymers) resulted in uniaxial nematic and smectic phases. Consequently, the next step was the synthesis of a new class of liquid crystalline side-chain polymers, in which the mesogenic moiety was laterally attached to the polymer backbone. The idea was that this side-on connection should be successful in hindering the rotation... 

The investigated samples included two different classes of side-chain polymers consisting of a polysiloxane backbone [14] with the mesogens either terminally attached [15] via a flexible spacer of four or six carbon atoms (called end-on 4 and end-on 6, respectively) or laterally attached [16] via spacers of six or eleven carbon atoms (called side-on 11 and side-on 6, respectively). Due to the relatively high glass transition temperature, the side-on 6 sample was only investigated in a mixture with a low molar mass liquid crystal (called side-on 6 mix). In addition to the pure polymer, the side-on 11 sample was also investigated in a mixture with a different low molar mass liquid crystal (called side-on 11 mix). 

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