Lyotropic Liquid Crystal Gels: Structure, Rheology, and Stimuli-Response

• Applicants: Professor Dr. Frank Gießelmann; Professorin Dr. Cosima Stubenrauch
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 289272413

After we succeeded in the first part of the project to produce lyotropic liquid crystal (LLC) gels with lamellar as well as nematic and hexagonal order in a controlled and reproducible way, the follow-up project will mainly focus on the specific properties and possible applications of LLC gels as water-based stimuli-responsive materials. LLC gels are the lyotropic counterparts of thermotropic liquid crystal gels and elastomers (LCEs) which are today the workhorses in the rapidly emerging fields of soft robotics and biomimetic actuation. In comparison to their thermotropic counterparts, LLC gels are cheap to prepare and compatible to aqueous media - they are thus expected to respond to a completely different range of chemical and biological stimuli. We consider this an extremely promising perspective that is well worth being placed in the focus of our follow-up project. The ultimate goal of the follow-up project is thus to explore the potential of LLC gels as stimuli-responsive materials. However, to successfully pursue this overall objective, two basic requirements must first be met, namely:(1) the availability of (mainly) nematic LLC gels with tailored thermal, structural and rheo-logical properties and(2) the successful preparation of aligned LLC gels with well-defined macroscopically anisotropic director configurations.The central research questions which will thus be addressed in the follow-up project are as follows:(a) How can (nematic) LLC gels with tailored thermal, structural and rheological properties be rationally designed? How does the composition of the LLC parent system (surfactant, cosurfactant, water) and the gelator concentration affect the clearing temperature, the sol-gel temperature, the orientational order parameter and the rheological properties of the LLC gels?(b) How can (nematic) LLC gels be processed into aligned specimens with a well-defined macroscopically anisotropic director configuration? Possible options are magnetic field alignment, surface alignment in restricted geometries, or shear alignment.(c) How do aligned LLC gels swell in water, aqueous solutions or other water-miscible solvents such as alcohols? How does the solvent absorption affect the phase behaviour? To which extent is the associated change in shape anisotropic?(d) How do aligned LLC gels respond to changes in temperature and, in particular, to temperature induced phase transitions? To which extent is the associated change in shape anisotropic and reversible? How fast is the thermo-mechanical response?Together with the results from the preceeding projects, the answers to these questions will lead to a first coherent picture of the preparation, the structure and the application of LLC gels, which allows a meaningful completion of the overall project.

• DFG Programme: Research Grants