Analysis of relaxation on polypropyleneglycols above vitrification temperature |
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Authors: | T M Usacheva N V Lifanova V I Zhuravlev V K Matveev |
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Institution: | (1) STC “Institute for Single Crystals”, National Academy of Science of Ukraine, 60 Lenina ave, Kharkiv, 61001, Ukraine;(2) Zaporizhia State Medical University, 28 Mayakovsky ave., Zaporizhia, 69059, Ukraine |
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Abstract: | The dielectric spectra of polypropyleneglycols H-(C3H6O)
N
p
-OH (PPGs), where N
p
= 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 n
DH. 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 m
DH. The relaxation time τDH at 303 K and 423 K and the parameters n
DH and m
DH 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 〈μc2〉 and di-PG, PPG-425 (N
p
= 7), and PPG-2025 (N
p
= 34) molecules 〈μm2〉 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, 〈μc2〉 and 〈μm2〉 on N
p
were studied. |
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Keywords: | |
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