Polymer-anchored crowns

A good deal of work has been done on polymeric crown ethers during the last decade. Hogen Esch and Smid have been major contributors from the point of view of cation binding properties, and Blasius and coworkers have been especially interested in the cation selectivity of such species. Montanari and coworkers have developed a number of polymer-anchored crowns for use as phase transfer catalysts. Manecke and Storck have recently published a review titled Polymeric Catalysts , which may be useful to the reader in gaining additional perspective. 

Some of the polymers slowly change their helicity in solution. A chiral crown ether-potassium ferf-butoxide combined system was reported to cause polymerization of methyl, tert-butyl, and benzyl methacrylate to form isotactic polymers that had high rotation values (164). Detailed scrutiny, however, raised questions about the result (135, 165). At first, in the presence of the initiator, the oligomers exhibit considerable activity, but after removal of the catalyst, the optical activity decreases. This decrease may be attributed to unwinding of the helixes in the chain the helicity could be caused by the anchored catalyst. 

In addition to strong-acid or weak-acid cation exchangers, crosslinked polymers carrying cyclic polyethers as anchor groups have been used for the separation of alkali and alkaline-earth metals, respectively. The structure of these stationary phases that are also based on silica was described in Section 3.3.1.4. A reasonable separation of alkali metals was obtained by Kimura et al. [38] on silica modified with poly(benzo-15-crown-5) using... 

The use of phase-transfer catalysts bound to polymeric supports has been reported. The catalytic functional groups anchored to the polymer were (i) quaternary ammonium salts (Fig. 13-la,b,c), (ii) phosphonium salts (Fig. 13-ld), (iii) Crown ethers (Fig. 13-le), and (iv) cryptands (Fig. 13-If). Chloromethylated, 2-4% cross-linked polystyrene and silica gel were used as the support polymers, and the catalyst groups were anchored either by the reaction with the corresponding amine or phosphine or by absorption. Spacer-arms were used for linking the crown ether and cryptand (Cinouini et al., 1976 Cinquini et al., 1975 Molinari et al., 1977 Tundo, 1977, 1978). 

There has been a worldwide realization diat nature-derived monosaccharides, disaccharides, oligosaccharides and polysaccharides can provide us with the raw materials needed for the production of numerous industrial consumer goods (Kunz, 1993 Varma, 2003 Pacitti, 2003). This section will deal with the role of sugar molecules anchored like pendants onto a synthetic polymer, reminiscent of the crown ether type molecules pendant on polystyrene and other synthetic chains which created a whole new area of research with far-reaching outcomes (Gokel and Durst, 1976 Varma, 1979 Varma et al, 1979 Smid et al, 1979a, Shah and Smid, 1978 Smid et al, 1979b Varma and Smid, 1977). 

Addic surfaces are a problem. It has been fotmd that crown ethers or calfacarenes can be applied as a primer to minimize this problem. As might be imagined from the stmcture of a cyanoacrylate, adhesion to low-surface-energy substrates such as polyethylene and polypropylene is a problem. However, it has been found that the application of a primer that contains tertiary aliphatic amines or other anionic polymerization initiators in an appropriate solvent provides a solution to this problem. The initiator diffuses into the surface of the plastic and initiates the polymerization in the plastic surface, thus providing an anchor for the polymer. ... 

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