Enhancement of the growth of polymer brushes via ATRP initiated from ions-releasing indium tin oxide substrates

Surface-initiated atom transfer radical polymerization (SI-ATRP) was used for grafting of model brushes (PNIPAM and PMMA) from various planar surfaces: indium tin oxide (ITO), glass and silicon oxide. All polymerizations for a given monomer were conducted at the same conditions in the presence of a sacrificial initiator. Both PNIPAM and PMMA brushes were found to be thicker when grafted from ITO with respect to the other surfaces demonstrating a significant influence of the ITO substrate on SI-ATRP kinetics. It was shown that ITO significantly increases the polymerization rate of the grafted chains due to not negligible desorption of metal ions which may undergo redox reactions also with the copper catalyst. Moreover, the molar masses of the grafted PNIPAM and PMMA chains were found generally larger (3-6 times for PNIPAM) than the ones of free polymers generated in solution, regardless of the substrate type, indicating significant differences in the rates of SI-ATRP and ATRP in the solution.