Preparation of reactive macroporous polymeric beads for high-performance liquid chromatography applications: Polymerization, surface modification and characterization

Several stationary phases for high performance liquid chromatography (HPLC) based on synthetic polymers with controlled pore structures and surface chemistries have been prepared and characterized.; The first part of the research is focused on the control of pore structure of reactive beads prepared from functional monomers such as 2,3-epoxypropyl vinylbenzyl ether and 2,3-epoxypropyl vinylbenzyl ether with divinylbenzene used as a crosslinker. Due to a relatively large difference in polarities of these two functional monomers, a new porogenic system had to be developed for the preparation of monodisperse beads from 2,3-epoxypropyl vinylbenzyl ether. In contrast, polymerization conditions similar to those used for the preparation of poly(styrene-co-divinylbenzene) beads can be used for the systems involving chloromethylstyrene and divinylbenzene. An extensive study of the effects of various polymerization parameters on the properties of these reactive beads was carried out in order to achieve fine control over the degree of functionalization and pore structure.; The second part of the research is focused on the surface modification of reactive beads prepared in the previous study for the HPLC separation of enantiomers. The performance of our chiral stationary phases (CSP) with brush-type selectors was comparable to the best silica-based chiral separation media. As a part of this study, polymeric CSPs with different linkages, tethers, loading levels, and backbone structures were prepared and characterized. Another series of CSPs were prepared from beads functionalized with a poly(propylene imine) dendrimer tether. A high coupling efficiency with the chiral selector was characteristic of the polymer support modified with dendrimers, and these dendritic supports demonstrated the substantial contribution of linkers with multiple functionalities originating from a single surface site to the selectivity and efficiency of the polymer based separation media.