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Proceedings Paper

Photoswitchable gas permeation membranes based on azobenzene-doped liquid crystals II. Permeation-switching characterization under variable volume and variable pressure conditions
Author(s): E. Glowacki; K. Hunt; D. Abud; K. L. Marshall
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Paper Abstract

Stimuli-responsive gas permeation membranes hold substantial potential for industrial processes as well as in analytical and screening applications. Such "smart" membrane systems, although prevalent in liquid mass-transfer manipulations, have yet to be realized for gas applications. We report our progress in developing gas permeation membranes in which liquid crystalline (LC) phases afford the active region of permeation. To achieve rapid and reversible switching between LC and isotropic permeation states, we harnessed the photomechanical action of mesogenic azobenzene dyes that can produce isothermal nematic-isotropic transitions. Both polymeric and low-molecular-weight LC materials were tested. Three different dye-doped LC mixtures with mesogenic azo dyes were infused into commercially available track-etched porous membranes with regular cylindrical pores (0.4 to 10.0 μm). Photoinduced isothermal phase changes in the imbibed material produced large and fully reversible changes in the permeability of the membrane to nitrogen with 5 s of irradiation at 2 mW/cm2. Using two measurement tools constructed in-house, the permeability of the photoswitched membranes was determined by both variable-pressure and variable-volume methods. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure (ideal sorption) relationship, with up to a 16-fold difference in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic-or vice versa. This approach is the first system offering reversible tunable gas permeation membranes.

Paper Details

Date Published: 17 August 2010
PDF: 10 pages
Proc. SPIE 7775, Liquid Crystals XIV, 77750G (17 August 2010); doi: 10.1117/12.860635
Show Author Affiliations
E. Glowacki, Univ. of Rochester (United States)
K. Hunt, Univ. of Rochester (United States)
D. Abud, Univ. of Rochester (United States)
K. L. Marshall, Univ. of Rochester (United States)

Published in SPIE Proceedings Vol. 7775:
Liquid Crystals XIV
Iam Choon Khoo, Editor(s)

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