Support Materials Other Than Polystyrene

Barett et al. [27] as well as Hanson and coworkers [28] used low molecular weight polyisobutylene to form polyisobutylene-supported catalysts:

An advantage of using polyisobutylene is solubility in a variety of nonpolar solvents at ambient temperatures. Also, the terminal double bond of polyisobutylene can be readily transformed into various useful groups for attachment of catalysts or reagents. Thus, polyisobutylene was used as a catalyst support for anchoring a sulfur-cation-sulfur Pd (II), as shown above. These catalysts were used to perform allylic substitution, Heck, and Sonogashira reactions [26]. Polyisobutylene was alsoused to support chiral bisoxazoline ligands for copper-catalyzed cyclopropanation reactions [27]. Other uses included catalysis of self-separating atom transfer radical polymerization [28], RCM catalysis [29], and catalysis of a chromium-based polycarbonate polymerization [30]. It is important to note that these polyisobutylene-supported catalysts exhibited close to or similar activity to their unanchored counterparts. In addition, they were readily recovered and reused without appreciable loss of activity. Na´jera and coworkers [34] used a commercial poly (styrene-alt-maleic anhydride) copolymer as support material. The copolymer was first reacted with hydroxylamine and then converted to a polymer-supported N-hydroxy succinimide. The product was then used in a peptide-coupling reactions. Low levels of racemization were reported. Addition of hexane allowed the removal of the polymeric material by filtration. 

The polymeric imide could then be reacted with primary amines or ammonia to form ammonium salts for a subsequent reaction with a carboxylic acid in the presence of a coupling reagent. It could then be converted to amides or functionalized as a uranium salt for use as polymer-supported peptide coupling. In addition, the anhydride was also reacted with di(2-pyrldyl) methylamine and formed a recoverable palladium catalyst for cross-coupling reactions that could take place in water.

Acrylic Polymers as Support Materials Various acrylic polymers and copolymers are also utilized as support materials. For instance, a copolymer of a fluoroacrylate monomers was prepared by Bergbreiter and coworkers to form a support material that is selectively soluble in fluorinated solvents [28–32].

The resulting polymer was then converted to a rhodium hydrogenation catalyst:

Numerous papers were also published on use of polyacrylamide and copolymers as support materials. Following is an example [33–36].

Bergbreiter reported using this material in mechanistic studies of the Heck reaction [33].

Tentagel, described above, is in wide use today in solid phase syntheses. Polyethylene glycol has also been attached to various other polymers to form support resins. For instance, Fre´chet and coworkers [37] used cross-linked methacrylate esters of ethylene glycol oligomers in a suspension polymerization to synthesize hydroxyl group functionalized beads. These beads swell well in a variety of polar solvents. Another example is that of Grubbs attaching a ruthenium metathesis catalyst to polyethylene [38]:

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مواضيع ذات صلة

Immobilized Nonenzymatic Catalysts

Immobilized Catalysts

Special Gels for Drug Release

Materials Based on Polystyrene

Polymer Supports for Reagents, Catalysts, and Drug Release

Degradation of Polymeric Materials by Ionizing Radiation

Oxidation of Chain-Growth Polymers

Oxidative Degradation of Polymers

Thermal Degradation of Cellulosic Materials

Thermal Degradation of Polyimides, Polyoxidiazoles, and Polyquinoxalines

Thermal Degradation of Aromatic Polysulfones

Thermal Degradation of Epoxy Resins