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Stability of nicotinate and dodecyl sulfate in a Lewis acidic ionic liquid for aluminum electroplating and characterization of their degradation products

Author:
Kosmus, Patrick, Steiner, Oliver, Goessler, Walter, Gollas, Bernhard, Fauler, Gisela
Source:
Electrophoresis 2016 v.37 no.7-8 pp. 1095-1100
ISSN:
0173-0835
Subject:
additives, alkanes, alkylation, aluminum, aluminum chloride, electrochemistry, electrophoresis, gas chromatography-mass spectrometry, ion exchange chromatography, ionic liquids, ions, sodium dodecyl sulfate, sulfates
Abstract:
Plating bath additives are essential for optimization of the morphology of electroplated layers. The ionic liquid 1‐ethyl‐3‐methylimidazolium (EMIM) chloride plus 1.5 mol equivalents of AlCl₃ has great potential for electroplating of aluminum. In this study, the chemical and electrochemical stability of the additives EMIM‐nicotinate and sodium dodecyl sulfate and their effect on the stability of EMIM was investigated and analyzed. Nicotinate and its electrochemical decomposition product β‐picoline could be detected and we show with a single HPLC‐UV‐MS method that EMIM is not affected by the decomposition of this additive. An adapted standard HPLC‐UV‐MS method together with GC‐MS and ion chromatography was used to analyze the decomposition products of SDS and possible realkylation products of EMIM. Several volatile medium and short chain‐length alkanes as well as sulfate ions have been found as decomposition products of SDS. Alkenium ions formed as intermediates during the decomposition of SDS realkylate EMIM to produce mono‐ up to pentasubstituted alkyl‐imidazoles. A reaction pathway involving Wagner–Meerwein rearrangements and Friedel–Crafts alkylations has been suggested to account for the formation of the detected products.
Agid:
5182239