Supramolecular Systems Based On Trisamides With Linear Perfluorinated Side Chains

Abstract

Supramolecular chemistry is the chemistry of molecular assemblies and intermolecular bonds. In contrary to the traditional chemistry, which deals with covalent chemical bonds, supramolecular chemistry is a matter of physical interactions between molecules. These non-covalent interactions determine the spatial organization of molecules, which can lead to the formation of larger well-defined supramolecular objects. In the supramolecular approach, molecules are able to self-assemble reversibly to defined supramolecular objects. The shape and functionality of these objects are imbedded in the molecular structure of the single molecules, which are influenced by the geometry of the molecule, side chains, and functional groups. In this context, this thesis provides a systematic study and detailed characterization of the thermal properties, phase behaviors, and mesophase structures of 1,3,5-benzenetrisamides (BTAs) and one 1,3,5-cyclohexanetrisamide (CTA) with linear perfluorinated side chains of different lengths. BTAs based on 1,3,5-triaminobenzene pass through plastic crystalline or liquid crystalline mesophases, which can mostly be identified as columnar phases. BTAs based on trimesic acid have one or more mesophases between the solid state and the isotropic phase, which are mostly of liquid crystalline appearance but cannot be clearly identified as columnar phases. All BTAs show an increase in transition enthalpy at the melting temperature and a simultaneous decrease at the clearing temperature with increasing side chain length. Comparison between the BTAs based on the different cores shows, that the BTAs based on 1,3,5-triaminobezene have lower clearing temperatures and much lower melting temperatures than the BTAs based on trimesic acid. The column distances of all perfluorinated BTAs increase linearly by a value of about 0.1 nm for every additional CF2 unit in the side chains. The CTA passes through an unidentified liquid crystalline mesophase and a columnar nematic phase before it finally changes into the isotropic phase upon heating. A selection of two BTAs based on 1,3,5-triaminobenzene with different side chain length and the CTA were processed by melt electrospinning to thin supramolecular fibers. The electrospinning parameters were varied to find the best parameter set for supramolecular fibers with good fiber shape and quality. The BTAs form the best fibers processed from the isotropic phase and at applied electric fields of 5.0 kV/cm and 6.7 kV/cm with average fiber diameters of about 0.4 µm up to 0.5 µm. The CTA forms thin fibers from the nematic phase with average fiber diameter of about 1.7 µm. Furthermore, the conditions for the processing of comparably thick fibers in the range of 5 µm up to 15 µm for direct force measurements of various BTA and CTA compounds within a collaboration with the chair of Physical Chemistry II at the University of Bayreuth should be found. All compounds could be processed to fibers of the desired thickness in an electric field with a strength in the range of 2.5 kV/cm up to…