Polymer Supports for Reagents, Catalysts, and Drug Release
Supports are materials that are used for immobilization of various reagents, catalysts, drugs for release. Many of them are specially prepared macromolecules. Reagents and catalysts on support find applications in organic syntheses, biochemical reactions, special separations, and analyses. They also find uses in medicine for drug release, etc. An advantage of immobilized polymeric reagents in chemical reactions is that they can be separated, often easily by filtration, from the products of this reaction. Cross-linked polymeric reagents have an additional advantage in that several different polymeric reagents can be used simultaneously without the functional groups being accessible to each other for interaction. Reactions of some compounds in solution require high dilutions. Immobilization, however, may permit the same reactions to be carried out at relatively high concentrations. Immobilization can also be very useful in syntheses that consist of many steps, where the undesired by-products from each step can simply be washed away. This avoids lengthy isolation and purification procedures [2]. Also, by immobilizing on a polymer, the macromolecule may provide microenvironmental effects to the attached species for the reactions. These may include special electronic and steric conditions that could be different from those existing in bulk or in solution. The chemical uses of polymeric reagents were originally classified by Patchornik according to the general type of reaction [1].
These are as follows:
1. Polymer-attached reagents are used in special separations to selectively bind one or a few species out of complex mixtures:
The polymer-bound compound is separated from the mixture and then released.
2. The polymer with a catalyst attached. Such catalysts can be enzymes, inorganic compounds, or organometallic compounds:
3. The polymeric reagent can also be used as transfer agents. Low molecular weight reactants transfer the functional moiety with the aid of the polymeric agent. This leaves the products in pure form after filtration and solvent removal.
4. The polymers are used as carriers or as blocking groups in syntheses [1]:
