Thin thermo-responsive polymer films onto the pore system of chromatographic beads via reversible addition-fragmentation chain transfer polymerization

Mesoporous silica heads modified with an azo initiator were used for grafting of a thermo-responsive polymer (poly-N-isopropylacrylamide, PNIPAAM) through reversible addition-fragmentation chain transfer (RAFT) mediated polymerization. The RAFT mediation allowed an efficient control of the grafting process and led to Suppression of the solution propagation preventing any visible gel formation. The resulting composites Were characterized by Fourier transform infrared spectroscopy, nitrogen adsorption analysis, elemental analysis, transmission and scanning electron microscopy and Lis thermo-responsive stationary phases in chromatography. The resulting material proved to be efficient for the separation of a mixture of five hydrophobic steroids and the retention time and efficiency of separation improved with increasing the column temperature above the lowest critical Solution temperature of PNIPAAM.