Poly(sodium 10-undecylenate) as a pseudo-stationary phase for micellar electrokinetic chromatography: effects of polymerization initiator

The use of micelle polymers, a class of polysoaps that have a polymerized hydrophobic interior and a charged hydrophillic exterior, as pseudo-stationary phases in micellar electrokinetic chromatography has received attention in recent years because of the advantages afforded by their stable structure. Micelle polymers based on 10-undecylenic acid and 10-undecenyl sulfate have been shown to provide highly efficient and selective separations. The polymers have been shown to be more polar than conventional micelles of sodium dodecyl sulfate. The synthetic yield of the free-radical polymerization is, however, very low. In this study, three different free-radical initiators of different hydrophobicity were used to initiate polymerization of sodium 10-undecylenate to form micellar polymers. The effect of the chemical initiator on synthetic yield and polymer chemical selectivity has been studied. More lipophilic initiators were found to reduce the synthetic yield and molecular weight of the polymers, possibly due to more efficient chain termination. The chemical structure of the initiator was found to have only minor effects on the chemical selectivity of the resulting polymers, indicating that another polymer property is responsible for the more polar character. Use of a very hydrophobic initiator was found to limit solubility such that the polymer could not be employed as a pseudo-stationary phase.