OXYANIONS CATALYZE GROUP-TRANSFER POLYMERIZATION TO GIVE LIVING POLYMERS

Oxyanions form a new class of catalysts for group-transfer polymerization (GTP) of acrylic monomers. Active catalysts in this class include aliphatic and aromatic carboxylates, phenolates, sulfinates, phosphinates, sulfonamidates, perfluoroalkoxides, nitrite, and cyanate. Catalytic activity is found in oxyanions whose conjugate acids have ap (in DMSO) within the range 4.5-23. Best results in terms of livingness and polydispersity of the resulting polymers are obtained with the lowest operable concentrations of the most active catalysts and with somewhat higher concentrations of catalysts of moderate activity. Bioxyanions (1:1 complexes of oxyanions with their conjugate acids) also are active but show reduced activity compared to the corresponding monooxyanions. They give better control of molecular weight than is obtained with the corresponding monooxyanions. In contrast to the more potent catalysts, the weaker catalysts show little activity at temperatures substantially below room temperature. Relative catalyst efficiency correlates well with pKa(DMSO) of the conjugate acids of the corresponding catalysts. The stereochemistry of PMMA prepared with oxyanion catalysts does not differ substantially from that of PMMA prepared with bifluoride catalysis. © 1990, American Chemical Society. All rights reserved.