Polymer supports, scope, pros and cons

Although soluble polymers have been investigated as supports [28, 29] they tend to bring with them separation problems which can be overcome, e.g. by micro- or ultra-filtration, but not conveniently so. On the other hand macroscopic polymeric objects have not been well investigated in this context, because they are not convenient for use in small laboratory-scale reactors and unless well designed are likely to offer only very low capacities. In contrast, however, macroscopic polymeric supports have proved invaluable for the immobilisation of reactive biomolecules and now form the basis of many domestic as well as clinical medical diagnostic kits [30]. 

R = reagent = byproduct P = product C = catalyst Pr = protecting group or 

These are typically between 10 pm and 1 mm in diameter, with species 250 pm being particularly useful for laboratory-scale reactions. They are essentially insoluble in all solvents and sufficiently macroscopic for the polymer handle to facilitate considerably manipulation of bound reactive groups. 

In engineering terms, polymer-supported species can be treated like any other heterogeneous system they can be used very flexibly in batch or column reactors, and in general are suitable for both gas or liquid phase reactions. Depending upon which mode of operation is chosen, a particular polymer structure and morphology might be more effective (see below). 

These tricks may be used to reduce side-reactions in the subsequent application or alternatively to enhance reaction rates or selectivity. Indeed, reactive species with only a transient existence in homogeneous solution can be stabilised for useful exploitation when attached to a polymer support. 

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