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 chains could be sparsely grown on a mica surface and then imaged, after appropriate solvent treatment, as nanoscale "molecular droplets," each droplet consisting 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. The 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-irradiated 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 the 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 sufficiently short, and an appropriate postpolymerization solvent treatment was used.