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Zeitschrift für Physikalische Chemie

International journal of research in physical chemistry and chemical physics

Editor-in-Chief: Rademann, Klaus

12 Issues per year


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Online
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2196-7156
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Volume 226, Issue 7-8

Issues

Structure-Property Relations of Liquid Crystalline Gels with ABA-Triblock Copolymers as Gelators

Robin Pettau / Thomas Müller / Maxim Khazimullin
  • 3 Ufa Research Center, Russian Academy of Science, Institute of Physics of Molecules and Crystals, Ufa, Russische Föderation
  • Other articles by this author:
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/ Ingo Rehberg / Hans-Werner Schmidt
Published Online: 2012-08-13 | DOI: https://doi.org/10.1524/zpch.2012.0284

Abstract

This paper reports on the influence of the structure of tailored ABA-triblock copolymers on physical gelation of the nematic liquid crystal 4'-n-pentyl-4-cyanobiphenyl (5CB), rheological properties, and the electro-optical response of the gels. The block copolymer gelators, comprised of two polystyrene A-blocks connected to a cyanobiphenyl-functionalized polyhydroxystyrene B-block, were synthesized by living anionic polymerization and functionalized by polymer analogous reactions. These block copolymers feature selective solubility. The B-block is soluble in the nematic and isotropic state of 5CB, whereas the polystyrene A-blocks are only soluble in the isotropic state. Consequently, upon cooling liquid crystalline gels are formed due to the controlled microphase-separation of the A-blocks. We show that the polymer composition and the different block lengths are important to vary the gel properties and the electro-optical response. It is confirmed that the gel formation correlates to the isotropic to nematic transition of 5CB for block copolymer gelators with sufficiently long A-blocks. Higher gel elasticity is obtained if gelators with short B-blocks are employed. The influence of the polymer network on the switching behavior of these liquid crystalline gels is investigated with respect to the electro-optical response in light scattering experiments. Intriguingly, these indicate a rearrangement of the nodes formed by the A-blocks under a strong electric field for block copolymers with short A-blocks.

Keywords: Block Copolymer Gelator; Liquid Crystalline Gel; Rheology; Electro-Optical Response

About the article

* Correspondence address: University of Bayreuth, Macromolecular Chemistry I, 95440 Bayreuth, Deutschland,


Published Online: 2012-08-13

Published in Print: 2012-08-01


Citation Information: Zeitschrift für Physikalische Chemie, Volume 226, Issue 7-8, Pages 645–664, ISSN (Online) 2196-7156, ISSN (Print) 0942-9352, DOI: https://doi.org/10.1524/zpch.2012.0284.

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