Grafting of silica with sulfobetaine polymers via aqueous reversible addition fragmentation chain transfer polymerization and its use as a stationary phase in HILIC

Porous silica particles of 3 microm diameter and 100 A nominal pore size were first activated for vinylic polymerization by functionalization with 3-methacryloyloxypropyl trimethoxysilane (MAPTMS) and thereafter dressed with zwitterionic grafts of the sulfoalkylbetaine type in the "grafting through" fashion by polymerizing 3-(2-(N-methacryloyloxyethyl)-N,N-dimethylammonio)propane sulfonate (SPE), using either free radical polymerization or controlled reversible addition fragmentation chain transfer polymerization (RAFT). Particles polymerized using RAFT had a lower overall coating which seemed to be more evenly distributed in the pore volume. Both approaches resulted in columns with similar separation properties in HILIC mode.