(95f) Redox-Triggered Orientational Responses of Liquid Crystals to Ozone Gas

Understanding how interfaces impact both equilibrium and dynamic properties of confined soft materials represents one of the central challenges facing the soft matter community. This is particularly true in the context of understanding the reorganization of stimuli-responsive systems. This presentation addresses this challenge with a focus on confined liquid crystalline materials, which combine key properties of crystalline solids (long-range order) and isotropic liquids (molecular mobility). Liquid crystals (LCs) are a promising class of chemoresponsive materials because the orientations of molecules (mesogens) within LCs can be changed by subtle interactions between mesogens and chemical functional surfaces.^1-3 We will show in this presentation that O₃ in the presence of water vapor can oxidize divalent metal cations (Mn²⁺, Co²⁺ and Ni²⁺) presented at solid surfaces. Our quantum chemical calculations predicted that the increase in oxidation state of the metal cations upon exposure to ozone would weaken the binding of nitrile-containing LCs to the solid surfaces, resulting in an orientational transition of the LC. We confirmed these theoretical predictions in subsequent experiments which revealed LC orientational and thus optical responses to parts per billion concentrations of O₃ gas. Additionally, by selecting different metal cation species, we will describe how this LC system can selectively respond to O₃ and another oxidizing gas agent, Cl₂. Overall, this presentation will describe important advances in the interfacial design of chemically-responsive LC systems from first-principles.

1. Shah, R. R.; Abbott, N. L. Science 2001, 293, 1296.
2. Hunter, J. T.; Abbott, N. L., Applied Materials and Interfaces, 2013, 6, 2362.
3. Szilvási, T.; Bao, N.; Nayani, K.; Yu, H.; Rai, P.; Twieg, R. J.; Mavrikakis, M.; Abbott, N. L., Angewandte Chemie International Edition, 2018, 57, 9665.