²H-NMR of the Induced Chiral Phases of Acrylate-Metacrylate Liquid Crystalline Copolymers

ABSTRACT

It is shown that the addition of 2 to 6 wt.% of a chiral dopant (CD) to a series of nematic copolymers (Pn) induces blue and cholesteric mesophases. The mesomorphic behaviour of various CD+Pn mixtures is investigated by polarized optical microscopy and the phase transition temperatures are determined by DSC measurements. Deuterium NMR spectra are recorded as a function of temperature within the mesophases and the spectral line shapes characteristic of different local orientational order parameters and orientational ordering processes of molecules in a magnetic field are observed depending on temperature, heating or cooling process, chiral dopant concentration, copolymer composition, and magnetic field strength.

Keywords:

• deuterium NMR
• polymeric liquid crystals
• blue phases
• cholestric phases
• induced chirality

Acknowledgments

We thank Prof. G. Galli for helpful discussions.