Synthesis of Polystyrene Brushes on Silicate Substrates via Carbocationic Polymerization from Self-Assembled Monolayers

This paper describes the synthesis of polystyrene (PS) brushes on silicate substrates via carbocationic polymerization from self-assembled monolayers (SAMs). Carbocationic initiators, 2-(4-(11-triethoxysilylundecyl)phenyl-2-methoxypropane and 2-(4-trichlorosilylphenyl)-2-methoxy- d 3 -propane, and their corresponding SAMs have been prepared. Monolayers were characterized by FTIR-ATR, contact angles, and X-ray reflectometry. Growth of PS brushes from these SAMs through carbocationic polymerization has been successfully achieved; factors that influence PS thickness include solvent polarity, additive, and TiCl 4 concentration. Sequential carbocationic polymerization on the same silicate substrate results in thicker PS films. FTIR-ATR study using a deuterated initiator indicates that the initiator efficiency is low, and the second carbocationic polymerization on the same sample involved initiation from both PS chain ends and unconsumed surface-immobilized initiators. Atomic force microscopy reveals a uniform and smooth PS brush surface with a roughness value of 0.3 nm (rms) for a 30 nm thick PS layer.