Polymerization in Clathrate Tunnel Systems: Stereocontrolled Polymerization of Unsaturated Monomers in Crystals of Tris(o-phenylenedioxy)cyclotriphosphazene

Acetylene, phenylacetylene, butadiene, isobutylene, divinylbenzene, styrene, and 4-bromostyrene have been trapped within the tunnel clathrate system of tris(o-phenylenedioxy)cyclotriphosphazene (I). For some of the adducts irradiation of the trapped monomers with ⁶⁰Co γ-radiation yielded short-chain polymer molecules within each tunnel. In specific cases (especially with butadiene) evidence was obtained that the polymerization products were stereoregular. Moreover, the polymer derived from divinylbenzene was uncross-linked in contrast to the form of this polymer obtained by other methods. The clathrate between 4-bromostyrene and I was studied in detail by variable-temperature broad-line ¹H NMR techniques and by single-crystal X-ray analysis. The results enable a preliminary correlation to be made between the monomer packing arrangement and the mode of polymerization.