Reversed hexagonal phase-structure in lithium phenylstearate

BARRON, C. and SPELLS, S. J. (1993). Reversed hexagonal phase-structure in lithium phenylstearate. Journal of Physical Chemistry, 97 (25), 6737-6744.

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The structure of the reversed hexagonal1 phase and the reversed hexagonal (H-2) --> (H2) reversed hexagonal (H-2) phase transition in anhydrous lithium phenylstearate have been investigated using FTIR spectroscopy. CH2 wagging vibrations from {gtg} and {gg} conformers indicate consistently smaller number of than would be expected from the rotational isomeric state model, although the number of {gtg} conformers approaches the predicted value at the H2 phase transition. The IR results enabled the alkyl chain extension to be calculated, as a function of tempemture. A new model of chain packing at the ionic core surface allowed the core radius (r(c)) to be estimated (5.6 angstrom less-than-or-equal-to r(c) less-than-or-equal-to 7.1 angstrom). In combination with the chain extension, an overall cylinder diameter was calculated. By the onset of the H2 transition, this dimension had decreased to a figure less than the X-ray lattice spacing. It is concluded that interdigitation of alkyl segments has then reduced sufficiently to allow translational and rotational freedom for the cylinders to become more closely packed. Changes in chain conformation are therefore seen as the driving force for the phase transition, allowing the X-my lattice spacing to decrease.

Item Type: Article
Research Institute, Centre or Group - Does NOT include content added after October 2018: Materials and Engineering Research Institute > Advanced Coatings and Composites Research Centre > Polymers, Composites and Spectroscopy Group
Identification Number:
Page Range: 6737-6744
Depositing User: Hilary Ridgway
Date Deposited: 12 May 2010 12:27
Last Modified: 18 Mar 2021 09:15

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