Isothermal Phase Transitions in Liquid Crystals Driven by Dynamic Covalent Chemistry.

Abstract

The dynamic nature of calamitic liquid crystals is exploited to perform isothermal phase transitions driven by dynamic covalent chemistry. For this purpose, nematic (N) arrays based on aldehyde1were treated with different amines (A-E) in an on-surface process, which resulted in different isothermal phase transitions. These phase transformations were caused byin-situimination reactions and are dependent on the nature of the added amine. Transitions from the N to crystal (1A,1E), isotropic (1B), and smectic (Sm) (1C,1D) phases were achieved, whiletheresultingmaterials feature thermotropic liquid crystal behavior. A sequential transformation from the N1to the Sm1Cand then to the N1Bwas achieved by coupling an iminationtoa transimination processes and adjusting the temperature. All of these processes were well characterized by microscopic, spectroscopic, and X-ray techniques, unlocking not only the constitutional but also the structural aspects of the phase transitions. This work provides new insights into designing constitutionally and structurally adaptable liquid crystal systems, paving the way toward the conception of programable evolutive pathways and adaptive materials.