Polymer-bound reducing agents, polymeric

Devaky and Rajasree have reported the production of a polymer-bound ethylenediamine-borane reagent (63) (Fig. 41) for use as a reducing agent for the reduction of aldehydes.87 The polymeric reagent was derived from a Merrifield resin and a 1,6-hexanediol diacrylate-cross-linked polystyrene resin (HDODA-PS). The borane reagent was incorporated in the polymer support by complexation with sodium borohydride. When this reducing agent was used in the competitive reduction of a 1 1 molar mixture of benzaldehyde and acetophenone, benzaldehyde was found to be selectively reduced to benzyl alcohol. 

Enzymes are covalently immobilized primarily onto the surface of the membrane exposed to the feed solution, known as the "active side" of the asymmetric membrane. In general, it is not clear whether reaction between enzymes and polymeric membranes via coupling agents simply results in enzyme attachment to the membrane, or if it leads to an enzyme-carrier network inside the polymer matrix. For the sake of simplicity let us assume that asymmetric membranes are used, that suitable active groups are available on the polymeric surface and that the membrane molecular weight cut-off is such that the active layer is enzyme-impermeable. In this way, even though their activity is often drastically reduced, surface bound enzymes are in close proximity to the substrate solution-thus reducing the mass transfer resistance to that associated with the boundary layer. When enzymes are covalently immobilized in the... 

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