SYNTHESIS OF POLYSILOXANES WITH ELECTRON-DONATING GROUPS BY ANIONIC RING-OPENING POLYMERIZATION

Anionic kinetically controlled ring opening polymerization of cyclotrisiloxane is explored as a method of synthesis of copolymers having the chain composed of dimethylsiloxane units and siloxane units bearing an uncharged nucleophilic (electron-donating, ED) group. Model monomers for these studies are derived from hexamethylcyclotrisiloxane (D3) in which one methyl group is replaced by the organophosphorus group of general formula -(CH2)nP(X)Ph2 where X is lone pair, O or S. This method is shown to give significant advantages over the thermodynamically controlled homopolymerization and copolymerization of nucleophile-substituted cyclosiloxanes which have so far been used for synthesis of ED substituted siloxane copolymers. The yield of the copolymers is much higher and the molecular weight distribution is narrow. The arrangement of the ED substituents along the chain, although not purely uniform, is much more regular as compared with the statistical distribution. The content of cyclic oligomers was higher than in the polymerization of unsubstituted D3, which is rationalized on the basis of intramolecular interaction of the counter-ion with the ED groups.