Optical Fingerprinting of Dynamic Interfacial Reaction Pathways Using Liquid Crystals

Area of Science:

• Interfacial chemistry
• Materials science
• Chemical reaction monitoring

Background:

• Interfacial reactions are crucial for synthesis but difficult to monitor in situ.
• Liquid crystals (LCs) have detected simple interfacial reactions via equilibrium orientations.
• Complex reaction pathways using nonequilibrium LC states remain unexplored.

Purpose of the Study:

• To investigate if liquid crystals (LCs) can report complex interfacial reaction pathways through nonequilibrium states.
• To explore the use of LCs for monitoring S_N2' reactions with varying nucleophile complexity.

Main Methods:

• Utilized S_N2' nucleophilic substitution reactions with a synthetic amphiphile and diverse amine nucleophiles.
• Analyzed the spatial and temporal optical responses of liquid crystals (LCs) to different reaction pathways.
• Investigated dynamic interfacial processes including adsorption/desorption and Marangoni stresses.

Main Results:

• All reactants and products induced the same equilibrium LC orientation.
• Each nucleophile generated a unique set of reaction pathways with distinct LC optical responses.
• Nonequilibrium LC states were linked to dynamic interfacial processes like adsorption, intermediates, and interfacial tension gradients.

Conclusions:

• Liquid crystals (LCs) can serve as sensitive reporters of complex interfacial reaction dynamics.
• The spatiotemporal optical outputs of LCs act as unique "optical fingerprints" for specific reaction pathways.
• This approach offers a novel method for in situ monitoring of interfacial chemical transformations.