Amino Acid and Peptide-Based Liquid Crystals: An Overview

The role of amino acids and peptides has found remarkable usage in both living systems and non-living materials, which have enabled its utility by virtue of crafting molecular architectures through covalent bonds and non-covalent interactions. In material chemistry, the role of peptides in Liquid Crystals (LCs) is profound, especially in the rapid construction of supramolecular hierarchical networks. The importance of LCs for a variety of societal needs leads to the synthesis of innumerable LCs by conventional mesogenic strategy and nonconventional molecular design principles. For example, electronic appliances, including flat panel TV displays, electronic notebooks, digital cameras, domestic devices, use LCs as an integral component for such applications. In addition, LCs are useful in biological systems, including stem cell research, sensors for bacteria, virus, and proteins. These accomplishments are possible mostly due to the non-conventional molecular design principles for crafting LCs using smaller molecular motifs. The usage of amino acids and peptides in LCs facilitates many intrinsic characteristics, including side-chain diversity, chirality, directionality, reversibility, electro-optical, columnar axis, stimuli-responsive complex molecular architectures. The next essential criteria for any LCs design for useful applications are room temperature LC (RT-LC); therefore, the quest for such LCs system remains highly significant. Evidently, there are around half a million liquid crystalline molecules; only a handful of RT-LCs has been found, as there is no simple, precise strategy or molecular design principles to obtain RT-LC systems. The smaller molecular motifs of amino acids and linear peptides as a structural part of mesogenic molecules led to many LC phases with properties, including lyotropic, thermotropic, and its applications in different realms. Therefore, this review serves as a compilation of Small Peptide-based LCs (SPLCs) exhibiting lyotropic and thermotropic phases with applications in the recent advancements.