Direct Controlled Polymerization of Ionic Monomers by Surface-Initiated ATRP Using a Fluoroalcohol and Ionic Liquids

Surface-initiated atom transfer radical polymerization (ATRP) of (2-methacryloyloxyethyl)trimethylammonium chloride (MTAC), 3-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatopropanesulfonate) (MAPS), and 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out in 2,2,2-trifluoroethanol (TFE) containing a small amount of 1-hexyl-3-methylimidazolium chloride at 60 °C to produce well-defined ionic polymer brushes and the corresponding free polymers with predictable number-average molecular weight (M_n, 1×10⁴?3×10⁵ g mol^?1) and narrow molecular weight dispersity (M_w/M_n<1.2). A first-order kinetic plot for ATRP of MTAC and MAPS revealed a linear relationship between the monomer conversion index (ln(M]₀/M])) and polymerization time. Reduction in polymerization rates was observed with an increase in ionic liquid concentration. The M_n of both poly(MTAC) and poly(MAPS) increased in proportion to the conversion. The sequential polymerization of MAPS initiated with the chain ends of poly(MAPS) produced the postpolymer with quantitative efficiency. The thickness of the polymer brush was controllable from 5 to 100 nm based on the M_n of the polymer. These results suggest the successful control of the polymerization of sulfobetaine-type methacrylates owing to the TFE and ionic liquids. In particular, the high affinity of TFE for the sulfobetaine monomers and polymers yielded a homogeneous polymerization media to improve surface-initiated polymerization generating the polymer brushes on the substrate surface as well as the free polymers formed in the solution. The effect on ATRP of the chemical structure of ionic liquids and ligands for copper catalyst was also investigated.