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Inclusion of Polymers within the Crystal Structure of Tris(o-phenylenedioxy)cyclotriphosphazene
journal contribution
posted on 1999-04-28, 00:00 authored by Harry R. Allcock, A. Paul Primrose, Nicolas J. Sunderland, Arnold L. Rheingold, Ilia A. Guzei, Masood ParvezTris(o-phenylenedioxy)cyclotriphosphazene was found to form hexagonal host−guest
inclusion adducts (clathrates) with the polymers: cis-1,4-polybutadiene, trans-1,4-polyisoprene, polyethylene, poly(ethylene oxide), and polytetrahydrofuran. Single-crystal X-ray
diffraction studies of both the polyethylene and poly(ethylene oxide) inclusion adducts
revealed the presence of individual polymer chains extended along tunnel-like voids within
the host lattice. Both polyethylene and poly(ethylene oxide) were incommensurate within
the tunnel-like voids preventing the exact elucidation of the polymer conformation. Average
repeat unit lengths calculated for these polymers suggest that both are in an extended
conformation. Both the polyethylene and poly(ethylene oxide) adducts crystallized from
benzene in the space group P63/m. Inclusion adducts of the five different polymers were
examined by differential scanning calorimetry (DSC) and powder X-ray diffraction. In each
case, the melting point of the inclusion adduct was higher than either the melting point of
the pure polymer or the pure host. The melting points of oligomeric 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 achieved through chemical decomposition of tris(o-phenylenedioxy)cyclotriphosphazene.
Linear polybutadiene was separated from a mixture with highly branched polybutadiene
through selective adduct formation.