A versatile route for surface modification of carbon, metals and semi-conductors by diazonium salt-initiated photopolymerization

This paper describes a general procedure to graft vinylic polymers by surface-initiating photopolymerization (SIPP) on diazonium-modified substrates. We have selected three surface-grafted aryl initiating systems (aryl = benzoyl phenyl (BP), dodecylphenyl (DDP), aminophenyl (AP)). The substrates were gold, stainless steel, glassy carbon and ITO. As previously found, surface-BP in the presence of dimethyl aniline (DMA, co-initiator) is very efficient on all substrates as judged by XPS. The surface-DDP/benzophenone system is extremely interesting as it provides a new method for coating vinylic polymers onto aryl-modified substrates. In this system the grafted DDP groups act as hydrogen donors. The simple gold-AP initiating system is interesting and needs further developments. All surfaces were characterized by XPS and surface compositions were correlated with wettability measurements for the Au–BP-polymethacrylate series. PM-IRRAS permitted to monitor the growth of poly(methacrylic acid) with SIPP time. Finally, adhesion aspects are covered in a preliminary study. We show here that polymer grafts resist complete delamination by the powerful swelling solvent methyl ethyl ketone, particularly when they are crosslinked. This adhesion test has never been applied to polymers bonded to surfaces through aryl diazonium coupling agents. ork constitutes a new step in designing well defined polymer grafts using aryl diazonium-derived photoinitiators. The method could be adapted on demand to a variety of substrates.