ZINC N-SUBSTITUTED PORPHYRINS AS NOVEL INITIATORS FOR THE LIVING AND IMMORTAL POLYMERIZATIONS OF EPISULFIDE

Zinc N-substituted porphyrins such as zinc N-methyl and -phenyl-5,10,15,20-tetraphenylpor- phyrins carrying the thiolate group as the axial ligand (R = CH3, X = SCH2CH2CH3 (lb), R = C6H5, X = SCH2CH2CH3 (2b)) brought about the living polymerization of 1,2-epithiopropane (propylene sulfide, PS), affording a polymer of very narrow molecular weight distribution. The number-average molecular weight of the polymer could be controlled by the mole ratio of the monomer reacted to the initiator. NMR studies demonstrated that the polymerization is initiated by the attack of the zinc-propylthio group of the initiator onto the monomer, generating a zinc thiolate as the growing species. The polymerization of 1,2- epithiopropane using lb as initiator proceeded with an immortal character in the presence of 1-propane- thiol, affording a polymer of uniform molecular weight with the number of the polymer molecules exceeding that of the initiator molecules. © 1990, American Chemical Society. All rights reserved.