Grafting Commercial Surfactants (Brij, CiEj) and PEG to Electrodes via Aryldiazonium Salts

Grafting commercial surfactants appears to be a simple way to modify electrodes and conducting interfaces, avoiding the synthesis of complex organic molecules. A new surface functionalization route is presented to build surfactant coatings with monolayer thickness grafting molecules considered as non-reactive. A monolayer of -SO2Cl functions (from a p-benzenesulfonyl chloride) was first electrografted. It showed a high reactivity toward weak nucleophiles commonly found on surfactant end-moieties such as hydroxyl groups (-OH), and it was used to covalently graft the following: (1) nonionic diblock oligomers (Brij or CiEj, CxH2x + (OCH2CH2)(n)OH with x = 16 and n = 23 for Brij58, x = 16 and n = 10 for Brij C10, and x = 16 and n = 2 for Brij52); (2) poly(ethylene glycol) (PEG) short chains (PEO9 for (OCH2CH2)(n)OH with n = 9) and mixed formula. The surface modification due to these molecular coatings was investigated in terms of wetting properties and interfacial electrochemistry characteristics (charge transfer resistivity, capacity, and ions dynamics). Built on flat and transparent thin chromium films, Brij and PEO mixed coatings have been proven to be promising coatings for electrochemical biosensor application such as for stabilizing a partially tethered supported biomimetic membrane.