Determination of the local disorder in the polyamorphic phases of triphenyl phosphite

The supercooled liquid of triphenyl phosphite (TPP) transforms into a second radiographically amorphous phase by isothermal treatment in the temperature range 215 - 230 K. We Studied the local Structural arrangernent of both the structural glass (phase aI) and the newly formed phase (aII) by doping triphenyl phosphite with deuterated hexamethyl benzene. Hexamethyl benzene exhibits a thermally activated, reorientational single particle motion in the glassy state of phases al and all. respectively. By line shape analyses of H-2 NMR solid-echo spectra as function of temperature, the distribution of activation energies was determined for both phases. Since the activation energy E-A is an immediate result of the local packing of a hexamethylbenzene molecule in the matrix its distribution G(E-A) is a clear Picture of the structural disorder. G(E-A) is very similar for both amorphous phases, thus their structural disorder must as well be similar. Furthermore, we present P-31 NMR spectra acquired for both amorphous phases and the crystalline modification of TPP. They are dominated by the chemical shift anisotropy. Although the chemical shift is an intramolecular property its anisotropy is different for the three phases indicating that each phase has a different average conformation of the TPP molecules.