Macromolecule-metal complexes ultrathin brushes with nanoscale protrusions grown from self-assembled monolayer by ATRP

Homopolymer and macromolecule-metal complexes (MMC) brushes on silicon wafers were successfully synthesized by the combination of self-assembly of the monolayer of initiator, atom transfer radical polymerization (ATRP) and coordination to metal ions. The initiator monolayer attached to silicon wafers was prepared by self-assembly of 3-aminopropyltriethoxysilane followed by amidation with α-bromopropionyl bromide, and permitted subsequent surface-initiated ATRP of butyl methacrylate (BMA) and acrylamide (AAM). From atomic force microscope (AFM) images it could be observed that the surface of poly(butyl methacrylate) (PBMA) brushes was uniform, while the surface of polyacrylamide (PAAM) brushes grew a large number of nanoscale protrusions. After coordination to metal ions, Pb²⁺ and Cd²⁺, MMC brushes of PAAM were formed, while the nanoprotrusions with different sizes and densities were observed on the surface of MMC brushes. X-ray photoelectron spectroscopy (XPS) was used to determine a molar ratio of 2.80C:1.00O: 0.75N for the PAAM brushes, in good agreement with the value (3.00C:1.00O:1.00N) based on the monomer AAM. Moreover, the occurrence of the new XPS signals of metal ions Pb²⁺ (139.1 and 143.8 eV) and Cd²⁺ (405.4 and 412.5 eV) verified the formation of the MMC brushes.