Electrokinetic chromatographic properties of amphiphilic copolymer poly (styrene-co-methacrylic acid) self-assembled micelle pseudostationary phase

Abstract

The amphiphilic copolymer poly (styrene-co-methacrylic acid) (P (St-co-MAA)) with molar ratios of 6:4 and 7:3 self-assembled to form micelles. The polymeric micelles were used as pseudostationary phase (PSP) in micellar electrokinetic chromatography ( MEKC). Their physicochemical properties and MEKC performance were investigated as well in the present work. The critical micelle concentration ( CMC) , polarity, surface charge density and hydrodynamic diameter were used to characterize the solution physicochemical properties, while the methylene group selectivity was evaluated with n-alkylphenone homologous series. The time window and linear solvation energy relationship (LSER) analysis were used to characterize the MEKC retention behavior and the selectivity. All of these were compared with poly (methyl methacrylate-co-methacrylic acid) (P (MMA-co-MAA)) with the molar ratio of 7:3 and sodium dodecyl sulfate (SDS) micellar systems. The results showed that P ( St-co-MAA) system had the minimum CMC, the widest time window and the best methylene group selectivity. LSER analysis results showed that the hydrophobic effect was the most important interaction between solutes and PSPs, and the hydrogen-bonding acidity was the second significant factor on selectivity and MEKC retention behavior. P (St-co-MAA) system, especially with the molar ratio of 7 :3, had the highest effective parameter in LSER and showed a high separation selectivity of PSP.