Use of Stable Free Radicals for the Sequential Preparation and Surface Grafting of Functionalized Macroporous Monoliths

Porous polymer monoliths have been prepared by polymerization of styrene and divinylbenzene in the presence of porogenic solvents initiated by 2,2,5-trimethyl-3-(1-phenylethoxy)-4-phenyl-3-azahexane. Although the polymerization reaction initiated by this alkoxyamine initiator is slower than that initiated by typical free-radical initiators, almost complete conversions were obtained at temperatures of 95 and 110 °C. The porous properties of the monolithic materials were easily controlled in a broad range by adjusting the composition of the porogenic solvents in the polymerization mixture. The capped radicals located at the surface of the pores of the monolith were used for subsequent grafting of functionalized linear chains from monomers such as tert-butyl methacrylate, chloromethylstyrene, or vinylpyridine at 110 °C. The extent of grafting within the pores could be controlled by adjusting the reaction time or diluting the monomer with an inert solvent.