Star Hydrophilic Polymer Brushed Nanoparticles Covalently Tethered on Si(100) Substrates via Surface-initiated Atom Transfer Radical Polymerization (ATRP)

摘要

Covalently tethered well-defined new three-arm star hydrophilic poly(ethylene glycol) monomethacrylate (PEGMA) brushed nanoparticles on silicon surface have been successfully prepared by (i) synthesis a novel type of three-arm star-shaped preceding initiator, trifunctional hydroxy-based N-allyl-3,4,5-trihydroxybenzamide (NATHB), (ii) UV-induced hydrosilylation of NATHB with the hydrogen-termined Si(100) (Si-NATHB surface), (iii) coupling of 2-bromo isobutyrl bromide with the hydroxyl of NATHB by the esterification to provide the initiators (Si– NATHB–R3Br) for the subsequent ATRP, (iv) surface-initiated ATRP of PEGMA and 2- hydroxyethl methacrylate monomethacrylate (HEMA) to give the linear Si–NATHB–g–P(PEGMA) brushes and the Si–NATHB–g–P(HEMA) surface, (v) further coupling of 2-bromo isobutyrl bromide with the hydroxyl of P(HEMA) by the esterification to produce the macroinitiators (Si– NATHB–g–P(HEMA)-R3Br) and (vi) surface-initiated ATRP of PEGMA to give the comb-shaped Si–NATHB–g–P(HEMA)–g–P(PEGMA) brushes surface. Kinetics study indicated that the chain growth of P(PEGMA) and P(HEMA) from the functionalized silicon surfaces was consistent with a "controlled" or "living" process. The chemical composition and functionality of the silicon surface were tailored by the well-defined star linear and comb-shaped P(PEGMA) brushes, which provide with this type of surface structures formed in three brushes under conditions of spatial constraints imposed by their chemical connection to a single grafting site. XPS spectra testify that the linear and comb-shaped P(PEGMA) have been grafted on the Si-NATHB surface. AFM imaging of the hydrophilic polymer brushed nanoparticles imaged distinctive morphology when they were prepared into linear and comb-shaped brushes structure.