Stereocontrolled Polymerization of Acrylic Monomers within a Tris(o-phenylenedioxy)cyclotriphosphazene Tunnel Clathrate

The ⁶⁰Co γ-ray-initiated polymerization of acrylic monomers (acrylic acid, acrylic anhydride, acrylonitrile, methyl acrylate, methyl methacrylate, methyl vinyl ketone) within the tunnel-clathrate system formed by tris(o-phenylenedioxy)cyclotriphosphazene (I) provides a general route to the synthesis of enhanced stereoregular polymers. A feature of the clathrate-mediated polymerization is that no radiation cross-linking of multifunctional monomers occurs, in contrast to some of the bulk polymerizations. For example, the clathrate polymerization of acrylic anhydride yielded a new linear polymer, whereas the analogous bulk polymerization gave a cross-linked matrix. The molecular weights of the clathrate-synthesized polymers were similar to those of polymers prepared in the bulk phase. Copolymers were also prepared within host I, and these were found to have a random sequence distribution, in contrast to copolymers prepared in the bulk phase.