Photografting of polymer monoliths by a crosslinking monomer

Abstract

The surface of fifteen polymethacrylate monolithic stationary phases has been modified by a post-polymerization UV-initiated grafting reaction with bifunctional poly(ethylene glycol)dimethacrylate monomers. An effect of crosslinking monomer length, its concentration in the modification mixture, and a time of the modification reaction have been selected to control the extent of modification by a design of experiments protocol. Hydrodynamic and kinetic properties of prepared columns were characterized by capillary liquid chromatography. Regression analysis of determined data revealed that there is only a minor effect of modification reaction on column permeability, as it is rather controlled by the composition of the polymerization mixture used to prepare generic monolith. On the other hand, the utilization of shorter crosslinking monomer increased the formation of small pores and minimized mass transfer resistance effect. Both column efficiency and mass transfer resistance also improved when a lower concentration of crosslinking monomer in the modification mixture was used. Photografting modification decreased a negative effect of mass transfer resistance related to a crosslink density gradient and allowed fast isocratic separations of dopamine metabolism-related compounds. Developed preparation protocol might be further utilized in the preparation of monolithic stationary phases in microfluidic devices.

Keywords: Design of experiments; Grafting; Hypercrosslinking; Mass transfer resistance; Polymer monolith; Small molecules.