AMBIENT-TEMPERATURE DIRECT SYNTHESIS OF POLY(ORGANOPHOSPHAZENES) VIA THE LIVING CATIONIC POLYMERIZATION OF ORGANOSUBSTITUTED PHOSPHORANIMINES

A new, ambient-temperature method for the direct synthesis of organo-s ubstituted polyphosphazenes is described. It involves the initiation o f a series of organophosphoranimines R(R')-XP = NSiMe(3) (3, R = Ph, R ' = X = Cl; 5, R = R' = Ph, X = Cl; 7, R = Me, R' = Et, X = Cl; 9, R = R' = CF3CH2O, X = Br) with catalytic amounts of PCl5 in CH2Cl2 to yie ld (after treatment with NaOCH2CF3 in the case of 3) the corresponding polyphosphazene species (N = PRR')(n) (4, R = Ph, R' = OCH2CF3; 6, R = R' = Ph; 8, R = Me, R' = Et; 10, R = R' = OCH2CF3) with narrow polyd ispersities. The molecular weights of the polyphosphazenes were contro lled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further additio n of monomer resulted in the formation of higher molecular weight poly mer. For monomers 7 and 9 optimum polymerization behavior was found to occur at 35 degrees C in the absence of solvent in the presence of ca talytic quantities of PCl5. These reactions proceeded to 100% completi on, while maintaining molecular weight control and narrow polydispersi tes. In the case of polymers 4, 8, and 10, which were synthesized with a 10:1 monomer to initiator ratio in CH2Cl2, the resultant polymers w ere analyzed by gel permeation chromatography (GPC) (4, M(n) = 2.9 x 1 0(3), polydispersity (PDI = M(w)/M(n)) = 1.07); 8, M(n) = 2.2 x 10(3), PDI = 1.31; 10, M(n) = 7.8 x 10(3), PDI = 1.23). Poly(diphenylphospha zene), (N = PPh(2))(n) (6), was insoluble in common organic solvents a nd was characterized by magic angle spinning (MAS) solid state P-31 NM R spectroscopy. The effects of side group steric bulk, electron-withdr awing or -donating properties, and leaving group types on the ambient- temperature cationic induced polymerizations are discussed.