Electrochemical Oxidation of Ethylenediamine: New Way to Make Polyethyleneimine-Like Coatings on Metallic or Semiconducting Materials

Abstract

A mechanism is proposed for the anodic polymerization of ethylenediamine (EDA). Initially, there occurs the formation of the radical cation NH 2 CH 2 CH 2 NH 2 ϩ• , followed by the breaking of the C-N bond, the expulsion of NH 2 • , and concomitant formation of the primary carbocation NH 2 CH 2 CH 2 ϩ or the aziridinium cation. This cation reacts with an NH 2 group of an EDA molecule, yielding a new amine which can be further oxidized. The product on the anode is a polyethyleneimine-like polymer. A similar product was found for diethylenetriamine, whose oxidation was studied too. Other pure -amines can also polymerize if they are primary amines and have vicinal alkyl groups which are secondary, i.e., have the formula NH 2 CH 2 RCH 2 NH 2 .

Covalent Tethering of Organic Functionality to the Surface of Glassy Carbon Electrodes by Using Electrochemical and Solid‐Phase Synthesis Methodologies

“…The absence of the corresponding cathodic peak on the reverse scan indicates that the amine radical cation generated during the forward scan undergoes fast chemical reaction, either binding to the GC surface (as shown in Scheme 2) or forming dimers or polymeric species in solution. [23] In subsequent scans, complete disappearance of the oxidation peak indicates that the electrode has been passivated by grafting of a Boc-EDA layer to the GC electrode surface. [3] The charge obtained by integrating the area under the peak (first scan) is about 100 times larger than that required to form a monolayer of Boc-EDA (2.0 nmol cm À2 ).…”

“…[4] This could be attributed to the occurrence of side reactions, such as dimerization of the radicals in the solution, which contribute to the overall current. [23] No attempt was made to measure the surface coverage of GC with the BocNHCH 2 C 6 H 4 or Boc-EDA linker, because the subsequent coupling of anthraquinone allows us to estimate the surface coverage directly using cyclic voltammetry.…”

“…All other reagents were obtained from Sigma-Aldrich and were used as received without any further purification. tert-Butyl N-(4-aminobenzyl)carbamate [20] and 4-(N-Boc-aminomethyl)benzoic acid [23] were synthesised by literature procedures.…”

“…[3] A subsequent quantification of unprotected EDA-modified carbon fibre by Antoniadou et al showed that only 1 % of free amino groups were available and could be coupled to an electroactive group. [23] Using Boc-EDA means that only the unprotected primary amine is bonded to the GC surface, as the protected amine is both less reactive and the bulky Boc group sterically hinders access to the active sites on the surface of GC. [4] To investigate the effect of the surface coverage of the linker on the final AQ surface coverage, we altered the surface coverage of the linker by varying the amount of charge passing during immobilisation of EDA-Boc and then coupled the anthraquinone to the different surfaces.…”

Electrodeposition of Insulating Thin Film Polymers from Aliphatic Monomers as Transducers for Biosensor Applications

“…The origin of the work concerning the electropolymerization of aliphatic bifunctional molecule comes back to the study of simple -amines which are known to form aminates (analog to hydrates' name) which are highly conductive electrolytes (Herlem et al 2000). Despite the potential window of primary amines (about 3.5 V on platinum electrode), ethylenediamine (EDA) shown abnormal electrochemical behavior when biased anodically.…”