Nanoscale single polymer chains on a chip: Poly(glycidylmethacrylate) grafted on silicon (100) surfaces

In previous studies reported in the literature it was shown that polymer ch ains could be sparsely grown on a mica surface and then imaged, after appro priate solvent treatment, as nanoscale "molecular droplets," each droplet c onsisting of a single polymer chain. With a view to eventual molecule-size devices on a chip, we wished to obtain such structures on silicon wafers. T he method employed was UV-initiated graft polymerization. Previous studies had shown that silicon wafers that were plasma-treated and then exposed to air formed peroxide-like compounds on the surface. These could then be UV-i rradiated in the presence of monomers to obtain surface-grafted polymer. It was expected that under sparse conditions of grafting, molecular droplets could be obtained in this way on silicon wafers. The monomer selected in th e present work was glycidylmethacrylate (GMA), of special interest because poly(GMA) is a potential biomolecule surface linker. Single chain molecular droplets were indeed obtained when the polymerization time was sufficientl y short, and an appropriate postpolymerization solvent treatment was used.