Functional Polymers from Vinylpolystyrene. Diels−Alder Reactions with Olefins

We describe a convenient route toward resins of cross-linked polystyrene bearing large numbers of carboxylic acid or anhydride, imide, acyl halide, or perhaloalkyl functional groups. These result from Diels−Alder reactions involving the site-isolated, residual vinyl aromatic units in divinylbenzene-rich copolymers (including commercial products). As shown by FT IR, solid-phase NMR, titration and elemental analysis, up to 2 mol of a good dienophile such as maleic anhydride bind to polymer beads by consecutive Diels−Alder/ene reactions (Wagner−Jauregg mechanism), while adducts are also possible from electron-poor dienes like hexachlorocyclopentadiene. Afterward, the new functional groups themselves prove accessible toward further modification. Optionally, the porous bead substrates can first be loaded with magnetic iron oxide to yield magnetically separable functional polymers.