Polymeric alkenoxy amino acid surfactants: I. Highly selective class of molecular micelles for chiral separation of beta-blockers

Two amino acid-based alkenoxy micelle polymers were synthesized for this study. These include polysodium N-undecenoxy carbonyl-L-leucinate (poly-L-SUCL) and polysodium N-undecenoxy carbonyl-L-isoleucinate (poly-L-SUCIL). The polymerization time and concentration of the synthesized micelle polymers were optimized by (1)H-nuclear magnetic resonance (NMR) and capillary electrophoresis (CE) experiments. Detailed physicochemical properties ((1)H NMR, critical micelle concentration (CMC), optical rotation, partial specific volume, aggregation number, and polarity) were determined, and these molecular micelles were introduced as a pseudostationary phase in micellar electrokinetic chromatography to study the molecular recognition and to develop a method for simultaneous separation of eight chiral beta-blockers. It is found that poly-L-SUCL gives overall better chiral resolution and wider chiral window than poly-L-SUCIL. After optimizing the type of micelle polymer, injection size and temperature, simultaneous separation and enantioseparation of eight beta-blockers were achieved in less than 35 min. A comparison with the amide-type surfactants of the same polar head group and alkyl chain length showed that carbamate-type surfactants always work better than the corresponding amide-type surfactant.