Anionic Polymerization of Acrylonitrile with Trivalent Phosphorus Compounds

Abstract

In order to see if the anionic polymerization of acrylonitrile initiated by trivalent phosphorous compounds is a living polymerization, and to see how high the molecular weight of polyacrylonitrile can be reached, the polymerization of acrylonitrile using triethylphosphite (TEP), phenyldiethoxyphosphine (PEP) and diphenylethoxyphosphine (DPP) was investigated. TEP was found to be a better initiator than the others, producing polymers with extremely high molecular weights. The polymerization system is a living type as the molecular weight increases until the system is exposed to air. However, the molecular weight polydispersity was in the range of 2.2–2.6 due to the complexity of initiation. The average molecular weight (Mw) reached 375,000, while that of a commercial polyacrilonitrile obtained by emulsion polymerization was 113,000. The polymer solutions obtained by the anionic polymerization became gel on standing, but they became sol when more solvent (DFM) was added and heated. The majority of polymers were slightly yellow due to the formation of imide linkages. The copolymerization with methylacrylate resulted in low molecular weight copolymers, with a ratio of acrylonitrile to methylacrylate units of 10.