Branched Fluoropolymer−Si Hybrids via Surface-Initiated ATRP of Pentafluorostyrene on Hydrogen-Terminated Si(100) Surfaces

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Abstract
Linear, branched, and arborescent fluoropolymer−Si hybrids were prepared via surface-initiated atom transfer radical polymerization (ATRP) from the 4-vinylbenzyl chloride (VBC) inimer and ClSO3H-modified VBC that were immobilized on hydrogen-terminated Si(100), or Si−H, surfaces. The simple approach of UV-induced coupling of VBC with the Si−H surface provided a stable, Si−C bonded monolayer of “monofunctional” ATRP initiators (the Si−VBC surface). The aromatic rings of the Si−VBC surface were then sulfonated by ClSO3H to introduce sulfonyl chloride (−SO2Cl) groups and to give rise to a monolayer of “bifunctional” ATRP initiators. Kinetics study indicated that the chain growth of poly(pentafluorostyrene) 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 linear and branched fluoropolymer brushes. Atomic force microscopy images revealed that the surface-initiated ATRP of pentafluorostyrene (PFS) had proceeded uniformly on the Si−VBC surface to give rise to a dense and molecularly flat surface coverage of the linear brushes. The uniformity of surfaces with branched brushes was controlled by varying the feed ratio of the monomer and inimer (VBC in the present case). The living chain ends on the functionalized silicon surfaces were used as the macroinitiators for the synthesis of diblock copolymer brushes, consisting of the PFS and methyl methacrylate polymer blocks.