Chromonic líquid crystals as precursors of polymer nanofibers

Abstract

Chromonic liquid crystals (CLCs) are a special kind of the well-known lyotropic liquid crystals. These mesophases are formed by multi-ring aromatic molecules like dyes, drugs or nucleic acids; which in the appropiate concentrations tend to aggregate forming columns. They have special properties that make them very interesting, including tailored optical properties. In this work, four different dyes (3,3’-Diethylthiadicarbocyanine iodide; 3,3’-Diethylthiacarbocyanine iodide; Pinacyanol chloride and Neutral Red) have been studied regarding their capacity for liquid crystal phase formation and their use as templates for oriented polymer nanofibers, some encouraging results were obtained. The synthesis strategy is based on a counterion exchange with a polymerizable ion ( acrylate), followed by self-assembly to obtain an homogeneous nematic phase which is used as medium for free-radical polymerization. Since in CLCs counterions are located in the periphery of the molecules, polymerization takes place in the surface of the columns of the dye’s nematic phase as template, so that polymeric nanofibers are obtained. Different techniques have been used for the characterization of the produced materials, such as IR spectroscopy, Small Angle X-ray Scattering (SAXS) and SEM imaging. The best results were those obtained using Pinacyanol acrylate as precursor, nanofibers of about 100-400 nm of thickness and a few microns length were synthetized. The polymeric nanofibers obtained are very suitable for further studies involving development of new optical polarizers, innovative higher performance solar cells and membranes. Moreover, the optical properties can be tuned depending on the precursor used, implying a very wide range of different possible applications making CLCs a very attractive field of study.