BINDING CATALYTIC SITES TO THE SURFACE OF POROUS POLYMERS AND SOME CATALYTIC APPLICATIONS

Polymer chains of quaternary onium salt have been bound to the internal surface of porous cross-linked polystyrene using two procedures based on the concentrated emulsion polymerization method. In the first procedure, surfactant molecules soluble in hydrophobic media and possessing an allyl or an acryloyl group in their hydrophilic moiety were synthesized and employed as emulsifiers in the preparation of gellike concentrated emulsions of water in styrene-divinylbenzene (ST-DVB). After polymerization, the surfactant molecules are present on the internal surface of the porous cross-linked polystyrene with the head groups residing on the surface. The obtained porous polymer was swollen in a methylene dichloride solution of (vinylbenzyl)trialkylammonium (or phosphonium) chloride containing AIBN as initiator. Then the system was polymerized, and as a result, the polymer chains of the quaternary onium chloride became grafted to the surface vinyl groups of the porous polymer. In the second procedure, the functional monomer vinylbenzyl chloride (VBC), was introduced into a partially polymerized gellike concentrated emulsion of water in ST-DVB, prepared by using a conventional surfactant (Span-80). During subsequent polymerization, polymers of VBC became grafted to the surface of porous poly(ST-DVB). Further, the benzyl chloride groups of poly(VBC) were transformed to styrenic groups through the Wittig reaction, thus obtaining a porous poly(ST-DVB) with surface-bound vinylbenzyl groups. Polymer chains of (vinylbenzyl)trialkylphosphonium chloride were then anchored to the porous polymer as in the first procedure. To each of the two kinds of surface-functionalized porous polymers, mono-sodium-sulfonated triphenylphosphine [Ph2P(C6H4-m-SO3Na)] was attached to a fraction of the polymer chains of quaternary onium salt as a coordination ligand for palladium acetate Pd(OAc)2. In this manner, two kinds of catalytic active sites, namely, quaternary onium groups and Pd(OAc)2 complexes, were located on the internal surface of the porous polymers. The polymer-supported bicatalysts have been employed in a vinylation reaction. The reaction activities and selectivities of the polymer-supported catalysts and of their homogeneous counterpart have been compared.