| Homogenous catalysts have are widely used to catalyze chemical reactions. However, often catalysts of this type are difficult to separate from the products and this limits their use in practice. To ease the separation of homogenous catalyst, the active center can be supported or tethered to an easily separable material, making a heterogenized homogenous catalyst. Many strategies are employed to this end including the use of polymers. Catalyst heterogenization has been reported by dissolution of the catalyst into the polymer, incorporation of the catalytically active center into the monomer from which the polymer is made, and grafting of the catalyst onto the chains of a preexisting polymer through chemically active functionalities on the polymer side chain. These approaches have many attractive properties, but can experience mass transfer limitations due to slow diffusion of reactants and products through the polymer network.;Our method of heterogenization uses crosslinked block copolymer gels. We demonstrate that crosslinked block copolymer gels are effective heterogenized catalysts for the Michael addition, ether cleavage and epoxide opening. One block of the copolymer is synthesized from a crosslinkable monomer that is not catalytically active. Another block is made of an organometallic monomer that can be made catalytically active. The use of mesopores was also explored by incorporating a third polymer species that can be degraded. These materials self-assemble into microphases that can then be fixed and degraded by exposure to an electron beam. In this manner we can use chain architecture to force active sites to the interface between the inert supporting phase and the degradable phase that promotes mass transfer.;We have developed a new strategy for immobilizing homogeneous catalysts in a manner that enables precise tunability of the reaction environment and mass transfer pathways. The parameters that control catalyst activity including size and arrangement of the active sites, pores and support structure are coded into the architecture of a block copolymer molecule. Catalysts are obtained by direct self-assembly of the block copolymer chains in bulk. Such catalysts are demonstrated to achieve higher activities than their homogeneous analogues. |
