Ionic Liquid Coatings for Titanium Surfaces: Effect of IL Structure on Coating Profile

• Published in: ACS applied materials & interfaces Vol. 7; no. 49; pp. 27421 - 27431
• Main Authors: Gindri, Izabelle M, Siddiqui, Danyal A, Frizzo, Clarissa P, Martins, Marcos A. P, Rodrigues, Danieli C
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16-12-2015
• Subjects: Hydrogen Bonding; Ionic Liquids - chemistry; Microscopy, Atomic Force; Photoelectron Spectroscopy; Titanium - chemistry; coatings; ionic liquids; atomic force microscopy; titanium; X-ray photoelectron spectroscopy
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.5b09309

Dicationic imidazolium-based ionic liquids (ILs) having bis­(trifluoromethylsulfonyl)­imide (NTf2) and amino acid–based (methionine and phenylalanine) anionic moieties were synthesized and used to coat titanium surfaces using a dip-coating technique. Dicationic moieties with varying alkyl chains (8 and 10 carbons) and anions with distinct characteristics were selected to understand the influence of IL structural features on deposition profile. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used in this study to help elucidate intermolecular interactions within ILs as well as between ILs and TiO2 surfaces and to investigate IL coating morphology. Charge concentration on IL moieties, as well as the presence of functional groups that can interact via hydrogen bond, such as carboxylate and amino groups, were observed to influence the deposition profile. ILs containing amino acids as the anionic moiety were observed to interact strongly with TiO2, which resulted in more pronounced changes in Ti 2p binding energy. The higher hydrophobicity of the IL having NTf2 as the anionic moiety resulted in higher adhesion strength between the IL coating and TiO2.