NMR Spectroscopic Study of Orientational Order in Imidazolium-Based Ionic Liquid Crystals

• We report on molecular and local orientational order of a series of imidazolium-based ionic liquid crystals exhibiting layered smectic A mesophase. Materials constituting of 1-dodecyl-3-methylimidazolium cation, and different counter-ions, were investigated. We apply two-dimensional C-13-H-1 dipolar NMR spectroscopy to quantify orientational order of C-H bonds of the organic cation. The experimental data supported the structural model of the interdigitated chains aligned with the smectic layer normal. Molecular order parameter S was found to increase in the anion sequence BF4- < I- < Br- < Cl-. This trend correlates well with ionic radius, negative charge delocalization, and hydrogen-bonding properties of the anions.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

ionic liquids

liquid crystals

ionic liquid crystals

molecular orientational order

nuclear magnetic resonance

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)