Abstract
Even using the same homo poly(N-isopropylacrylamide) immobilized silica beads as stationary phases, terminal functional group and chain length significantly affected temperature-dependent elution behavior of steroids.
Highlights
Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most studied temperature-responsive polymers, and exhibits temperature-dependent phase transition in aqueous solutions at its lower critical solution temperature (LCST) of 32 C.1 PNIPAAm chains are hydrated and hydrophilic below the LCST and dehydrated and hydrophobic above the LCST, which means that its hydrophobicity/hydrophilicity can be controlled by temperature.[2,3] Taking advantage of this characteristic, temperature-responsive chromatography systems based on a PNIPAAm-modi ed stationary phase were developed.[4]
These results indicate that the chain length and terminal functional group on the outermost surface of the polymer have a critical effect on the characteristics of polymer modified silica bead interfaces
PNIPAAm with two chain lengths having terminal dodecyl trithiocarbonate groups was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization,[36] as shown in Scheme 1
Summary
Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most studied temperature-responsive polymers, and exhibits temperature-dependent phase transition in aqueous solutions at its lower critical solution temperature (LCST) of 32 C.1 PNIPAAm chains are hydrated and hydrophilic below the LCST and dehydrated and hydrophobic above the LCST, which means that its hydrophobicity/hydrophilicity can be controlled by temperature.[2,3] Taking advantage of this characteristic, temperature-responsive chromatography systems based on a PNIPAAm-modi ed stationary phase were developed.[4]. We have focused on the effect of the terminal functional group and chain length of PNIPAAm via RAFT polymerization gra ed onto silica beads on the HPLC separation of steroids. The LCST of PNIPAAm can be affected by co-monomer composition,[5] terminal group,[22] and molecular weight.[39] The contribution of the terminal dodecyl trithiocarbonate moiety increases in the case of 5000-D, which has a relatively short chain length.
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