(73j) Direct Observations of the Double-Layering Molecular Structure of Mica-Confined Ionic Liquids | AIChE

(73j) Direct Observations of the Double-Layering Molecular Structure of Mica-Confined Ionic Liquids

Authors 

Wang, B. - Presenter, University of Pittsburgh
Li, L., University of Pittsburgh
Since the interface between ionic liquids (ILs) and solids always plays a fundamental role in coating, lubrication, energy storage, catalysis, etc., it is critical to uncover the detailed molecular arrangements of ILs confined to solid surfaces. Here, we report direct observations of unique quantized growths of mica-confined ILs with various cation alkyl chain lengths, i.e., [Emim][FAP], [Bmim][FAP], and [Hmim][FAP], under AFM. The IL films initially only cover more solid surface areas at the constant film thickness of 2 monolayers (ML) until a quantized increase in the film thickness by 2 ML. The cation alkyl chain length in [Emim][FAP], [Bmim][FAP] and [Hmim][FAP] has no impact on the nanofilm morphology at the thermodynamic equilibrium states. Based on the directly-observed thickness results from AFM, we propose a double-layering interfacial molecular arrangement of IL cations and anions on the mica surface. Meanwhile, the time-dependent AFM results also demonstrate the effect of the alkyl chain length in the cations on the spreading kinetics of mica-confined IL nanofilms. The spreading is slower for ILs with longer alkyl chains.