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Self-assembled liquid-crystalline gels designed from the bottom up

Nature Materials volume 3, pages 177–182 (2004)Cite this article

Abstract

Liquid crystals are often combined with polymers to influence the liquid crystals' orientation and mechanical properties, but at the expense of reorientation speed or uniformity of alignment. We introduce a new method to create self-assembled nematic liquid-crystal gels using an ABA triblock copolymer with a side-group liquid-crystalline midblock and liquid-crystal-phobic endblocks. In contrast to in situ polymerized networks, these physical gels are homogeneous systems with a solubilized polymer network giving them exceptional optical uniformity and well-defined crosslink density. Furthermore, the unusually high-molecular-weight polymers used allow gels to form at lower concentrations than previously accessible. This enables these gels to be aligned by surface anchoring, shear, or magnetic fields. The high content of small-molecule liquid crystal (≥95%) allows access to a regime of fast reorientation dynamics.

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Figure 1: Molecular structure of the nematic solvent 5CB and the ABA liquid crystal polymers.
Figure 2: The phase behaviour of the nematic gels.
Figure 3: Neutron-scattering patterns for homopolymers dissolved in perdeuterated 5CB33,34 at a concentration of 5 wt%.
Figure 4: Conoscopic images of 20-wt% ABASiCB5 gel, 400 μm thick, in 5CB at 25 °C.
Figure 5: Photos and cross-section schematics illustrating the electro-optic switching of a 5-wt% ABASiCB4 gel in a 25-μm gap.
Figure 6: Transient electro-optic properties of a 5-wt% ABASiBB, 25-μm-thick layer, under application of a.c. fields at 1,000 Hz.

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Acknowledgements

The authors acknowledge financial support from the United States Air Force Office of Scientific Research Liquid Crystal Multidisciplinary Research Program of the University Research Initiative (LC-MURI) (f4962-97-1-0014), the ARCS Foundation, the United States National Science Foundation Department of Materials Research (DMR-0216491), and the United States National Defense Science and Engineering Graduate (NDSEG) Fellowship. We would like to thank Steven Smith of Proctor and Gamble for providing us with 1,2-polybutadiene samples.

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Author notes

  1. Neal R. Scruggs and Rafael Verduzco: These authors contributed equally to the work

Authors and Affiliations

  1. California Institute of Technology, 1200 East California Boulevard, Pasadena, 91125, California, USA

    Michael D. Kempe, Neal R. Scruggs, Rafael Verduzco & Julia A. Kornfield

  2. Argonne National Laboratory, 9700 South Cass Avenue, Argonne, 60439, Illinois, USA

    Jyotsana Lal

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  1. Michael D. Kempe
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Correspondence to Julia A. Kornfield.

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Kempe, M., Scruggs, N., Verduzco, R. et al. Self-assembled liquid-crystalline gels designed from the bottom up. Nature Mater 3, 177–182 (2004). https://doi.org/10.1038/nmat1074

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