Liquid crystals with novel terminal chains as ferroelectric hosts

Cosquer, Guirec Yann

Abstract

Changes to the molecular structure of liquid crystals can have a significant effect upon their mesomorphism and ferroelectric properties. Most of the research in liquid crystal for display applications concentrates on the design and synthesis of novel mesogenic cores to which straight terminal alkyl or alkoxy chains are attached. However, little is known about the effects upon the mesomorphism and ferroelectric properties ofvarying the terminal chains. The compounds prepared in this work have a common core - a 2,3-difluoroterphenyl unit with a nine-atom alkyl (nonyl) or alkoxy (octyloxy) chain at the 4-position, but with an unusual chain at the 4”-position. In some cases the terminal chain contains hetero atoms such as silicon, oxygen, chlorine and bromine or has a bulky end group. In total 46 final materials were synthesised in an attempt to understand the effect of an unusual terminal chains on mesomorphism and for some o f these compounds the effect upon the switching times when added to a standard ferroelectric mixture were investigated. It was found that most compounds containing a bulky end group only displayed a smectic C phase, compounds with a halogen substituent as an end unit displayed a smectic A phase and that increasing the chain flexibility by introducing an oxygen atom in the chain reduces the melting and clearing points. The electro-optical measurements carried out
on ferroelectric mixtures containing a bulky end group compound showed that shorter switching times were produced than for the ferroelectric mixture containing a straight chain compound. It is suggested that a bulky end group diminishes the extent o f inter­ layer mixing in the chiral smectic C phase and therefore the molecules move more easily with ferroelectric switching.

Citation

Cosquer, G. Y. Liquid crystals with novel terminal chains as ferroelectric hosts. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4223925

• Thesis Type: Thesis
• Deposit Date: Feb 11, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4223925
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Feb 1, 2000