Z. Phys. Chem. 226 (2012) 645–664 / DOI 10.1524/zpch.2012.0284  by Oldenbourg Wissenschaftsverlag, München Structure-Property Relations of Liquid Crystalline Gels with ABA-Triblock Copolymers as Gelators By Robin Pettau 1 , Thomas Müller 2 , Maxim Khazimullin 3 , Ingo Rehberg 2 , and Hans-Werner Schmidt 1 , 4, ∗ 1 Macromolecular Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany 2 Experimental Physics V, University of Bayreuth, 95440 Bayreuth, Germany 3 Institute of Physics of Molecules and Crystals, Ufa Research Center, Russian Academy of Science, Ufa, Russia 4 Bayreuth Institute of Macromolecular Research and Bayreuth Center for Colloids and Interfaces, University of Bayreuth, 95440 Bayreuth, Germany Dedicated to Matthias Ballauff on the occasion of his 60 th birthday (Received June 1, 2012; accepted in revised form July 15, 2012) (Published online August 13, 2012) Block Copolymer Gelator / Liquid Crystalline Gel / Rheology / Electro-Optical Response 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 anal- ogous 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. 1. Introduction In his early work, Matthias Ballauff investigated mixtures of thermotropic nematics and ﬂexible, non liquid crystalline polymers [1 – 4]. While isotropic polymers may be * Corresponding author. E-mail: hans-werner.schmidt@uni-bayreuth.de