Inclusion of polymers within the crystal structure of tris(o-phenylenedioxy)cyclotriphosphazene

Tris(o-phenylenedioxy)cyclotriphosphazene was found to form hexagonal host- guest. inclusion adducts (clathrates) with the polymers: cis-1,4-polybutadi ene, trans-1,4-polyisoprene, polyethylene, poly(ethylene oxide), and polyte trahydrofuran. Single-crystal X-ray diffraction studies of both the polyeth ylene and poly(ethylene oxide) inclusion adducts revealed the presence of i ndividual polymer chains extended along tunnel-like voids within the host l attice. Both polyethylene and poly(ethylene oxide) were incommensurate with in the tunnel-like voids preventing the exact elucidation of the polymer co nformation. Average repeat unit lengths calculated for these polymers sugge st that both are in an extended conformation. Both the polyethylene and pol y(ethylene oxide) adducts crystallized from benzene in the space group P6(3 )/m. Inclusion adducts of the five different polymers were examined by diff erential scanning calorimetry (DSC) and powder X-ray diffraction. In each c ase, the melting point of the inclusion adduct was higher than either the m elting point of the pure polymer or the pure host. The melting points of ol igomeric polyethylene and poly(ethylene oxide) inclusion adducts increased as the molecular weight of the included oligomers increased. Removal of cis -1,4-polybutadiene and poly(ethylene oxide) from the host lattice was achie ved through chemical decomposition of tris(o-phenylenedioxy)cyclotriphospha zene. Linear polybutadiene was separated from a mixture with highly branche d polybutadiene through selective adduct formation.