Grafting of polymeric platforms on gold by combining the diazonium salt chemistry and the photoiniferter method

Abstract

The grafting of stable and strongly attached polymeric platforms on gold is a key factor for successful applications in biology, catalysis and sensing. Here, we report on the use of a combination of the iniferter method and the diazonium salt chemistry for preparing smart polymeric platforms attached through covalent bonds on gold. For this, bifunctional molecules bearing aryl diazonium coupling agents for anchoring on gold and N,N-diethyldithiocarbamate groups for initiating the growth of polymer chains were used. These two moieties were separated by oligo(ethylene oxide) spacers of various lengths allowing a fine tuning of the hydrophilic properties of the grafted photoinitiator layers. Cross-linked copolymers of methacrylic acid (MAA) and N,N′-methylenebisacrylamide (MBAm) were then grown from the gold surfaces under UV light. The polymer films were characterized in terms of chemical composition and wettability by X-ray photoelectron spectroscopy and contact angle measurements, respectively. The grafting procedure was simple, rapid and effective in producing polymer-grafted Au surfaces at room temperature. The diethyldithiocarbamil groups remaining at the end of the growing tethered chains could then be easily exchanged by a UV-light induced radical-exchange experiment in order to obtain terminal amino moieties able to immobilize citrate-capped gold nanoparticles, through electrostatic interactions. The results obtained in the present work highlight the efficiency of the diazonium salt chemistry coupled to the photo-iniferter based surface grafting approach to spontaneously functionalize gold surfaces through covalent bonds. This strategy open new opportunities for the preparation of “smart” hybrid platforms made of pH-responsive polymers and nanoparticle assemblies.