Babak M. Synthesis of chiral dopants for liquid crystal compositions on the base of dianhydrohexitol and lupane molecular platforms

The present thesis is devoted to the synthesis and investigation of molecular structure of new chiral dopants for induced cholesteric liquid crystal compositions. In the series of ether-ester-substituted 1,4:3,6-dianhydrohexitols in 4'-pentyl-4-cyanobiphenyl nematic solvent , the most helical twisting power was found for bis-esters. Lesser values were found for mixed ether-esters with certain configuration. Other ethers, ether-esters and 5-aryl-1H-pyrrolo[3,4-d]triazolyl-4,6-diones of 1,4:3,6-dianhydrohexitols revealed noticeably smaller values. A number of new alpha,beta-unsaturated ketones of the lupane series were synthesized by aldolcrotonic condensation of allobetulone with aromatic and heterocyclic aldehydes. Chemical modification of 2-ylidene derivatives of allobetulone led to new chiral dopants with high ability to induce cholesteric helix in nematic liquid crystals.The steric structure of obtained substances was determined by X-ray analysis. It is shown how the value of twisting power in this series of compounds varies depending on the spatial arrangement relative to the aryl moiety of the chiral core.