Methacryloylpropyl-(beta)cyclodextrin and vinylpyrrolidone copolymers: Synthesis and characterization as potential chiral selector

The free radical copolymerization of vinylpyrrolidone (VP) with 2-hydroxy-3-methacryloyloxypropyl (beta)-cyclodextrin ((beta)W7 MAHP), a derivative of hydroxypropyl (beta)-cyclodextrin (CD) substituted by polymerizable methacryloyl groups, is carried out in water by varying the molar ratio of the comonomers. It is found that the higher the molar ratio of (beta)W7 MAHP to VP, the larger the molar mass of the water-soluble copolymer. A size exclusion chromatography analysis coupled with multiangle laser light scattering detection (SEC-MALLS) suggests that VP-rich copolymers with a mass-average molar mass (MM) of about 2.5 * 10^4 g mol^-1 may consist of (beta)W7 MAHP dimers, trimers, and oligomers containing few CD units whereas (beta)W7 MAHP rich copolymers with an MM of about 5.5 * 10^6 g mol^-1 are likely to be dominated by crosslinked polymer materials. (beta)W7 MAHP-co-VP copolymers coated on porous silica are used as highperformance liquid chromatography chiral selectors. The effects of the structural features of the guest molecule and the characteristics of the chiral stationary phases on the retention and resolution are evaluated. SEC-MALLS detection shows that, by varying the comonomer feed, copolymers with different molar masses and macromolecular structures are formed. The chiral separation ability of Copo VP is evaluated toward enantiomers having one or more aromatic rings as a function of the amount of copolymer adsorbed onto the silica surface, the (beta)W7 MAHP content, and the concentration of solute. It is clear that the column combining the greater amounts of adsorbed copolymer and (beta)W7 MAHP exhibits better resolving power. Moreover, the size, geometry, and functionality of the guest molecule are important factors that strongly affect the enantioselectivity.