ABSTRACT
Macroporous resins have been used for many years in ion exchange applications, as polymeric adsorbents and for reverse-phase chromatography purifications. Macroporous resins are defined as a class of resin having a permanent well-devel-oped porous structure even in the dry state (if they survive in this form). These resins are typically prepared by suspension polymerization of Styrene-DVB mixtures containing a porogen or diluent (an organic solvent in general) at a well-defined ratio providing resin beads with a defined pore structure. Removal of the porogen at the end of the polymerization provides a heterogeneous PS matrix with some areas completely impenetrable and others free of polymer. Macroporous resins are characterized by a hard, rough surface having a defined total surface area. Unlike Merrifield resin, these materials do not need to swell to allow access of reagents through the PS network as they possess a permanent porous structure that can be accessed by essentially all solvents; even solvents such as water can penetrate the macroporous PS-DVB matrix. When a solvent penetrates a macroporous resin, the polymer matrix tends to swell to some extent and often rapidly because the permanent holes provide rapid access through the network. However, due to the nature of the beads swelling takes place in the pores and little swelling of the beads takes place. Due to the nature and speed of diffusion, macroporous resins show much better resistance to osmotic shock during swelling and deswelling processes.
