Polimery 1998, No 1, 11
A review covering polymer systems applicable as PTC, subdivided into three groups: (i) polymeric phosphoramides, acetamides, sulfoxides, sulfones and pyridines used as PTC in the unmodified form (ineffective in the monomer form); (ii) onium salts, crown ethers and cryptands supported on insoluble polymer matrices; (iii) soluble polymers containing aprotic solvent moieties such as dimethyl sulfoxide, sulfolane, N,N-dimethylformamide, N,N-dimethyl acetamide, etc. Although group ii includes classical PTC species, catalyst activity is still affected by structural factors like the degree of crosslinking of polymer matrix, concentration and lipophilicity of active groups, length of the methylene chain spacer between the polimer and the active group, etc. Immobilization on a polymer matrix eliminatek problems of separation and recycling of PTC catalysts. Mechanical strength and chemical stability of immobilized PTC are then crucial.
Keywords: phase-transfer catalysts (PTC), onium salts, crown ethers, cryptands, polymer-supported aprotic solvents, catalyst activity