Synthesis and characterisation of novel aromatic ester swallow-tailed cholesteric liquid crystal polymers.

In this paper, two novel aromatic ester swallow-tailed liquid crystal monomers M₁ and M₂ and a straight chain cholesteric liquid crystal monomer M₃ were designed and synthesised. Two series of liquid crystal polymers, P₁ series and P₂ series, were graft-copolymerised with M and polymethylhydrosiloxane (PHMS). All the synthesised liquid crystal monomers and polymers were characterised by IR and ¹H NMR and confirmed to the predicted molecular structure. The liquid crystal and thermal properties of the synthesised compounds were tested by DSC, POM, TGA and optical rotation. The results show that the monomer M₁ is a monotropic nematic liquid crystal, and the Schlieren texture appears during the cooling process. M₂ is an enantiotropic nematic liquid crystal with filamentous and schlieren texture. M₃ is a thermotropic enantiotropic cholesteric phase with oily streak and focal cone texture. Both polymers P₁ and P₂ show typical Grand-Jean texture, and with the increase of monomer M₃ content, the polymer clearing point temperature Ti increases continuously, the liquid crystal mesophase range widens, and the specific rotation value increases. [ABSTRACT FROM AUTHOR]