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Journal of Structural Chemistry

2009 year, number 5


T. M. Usacheva, N. V. Lifanova, V. I. Zhuravlev, V. K. Matveev
Keywords: polypropyleneglycols, dielectric spectra, dipole moments of clusters, dipole moments of molecules, intermolecular interactions
Pages: 967-979


The dielectric spectra of polypropyleneglycols H-(C3H6O)Nр-OH (PPGs), where Nр = 1, 2, 3, 7, 12, 17, 20, 34, 69, were analyzed in terms of the Dissado−Hill (DH) cluster model above the vitrification temperatures. In PPGs, the structural clusters are associates formed by intra- and intermolecular hydrogen bonds. The activation processes of cleavage and formation of intermolecular hydrogen bonds in clusters, when the total number of intermolecular hydrogen bonds changes, are characterized by the parameter nDH. The fluctuation processes of simultaneous exchange of molecules between adjacent clusters correspond to redistributions of intermolecular hydrogen bonds between clusters, when only the position but not the total number of intermolecular hydrogen bonds changes, and are characterized by the parameter mDH. The relaxation time τDH at 303 K and 423 K and the parameters nDH and mDH of the dielectric spectra were calculated. The activation energies of relaxation in the range 210-323 K were determined. The mean statistic squares of the dipole moments of clusters and di-PG, PPG-425 (Nр = 7), and PPG-2025 (Nр = 34) molecules at 303 K and 423 K were calculated. The number of the units of the oxypropylene chains involved in relaxation was determined. The dependence of the parameters of the DH model, relaxation energies, , and on Nр were studied.