Abstract:The hydration of synthetic poly(P-hydroxy 1,3 propylenephosphate) in hydrogen and mixed H § § forms has been studied by means of the pulsed NMR method. This polymer may be regarded as a simplified model of natural teichoic acids appearing in a cell wall of gram-positive bacteria. The investigations of nuclear magnetic relaxation of water protons in polymer gels prove the existence of two phases of water. One is water strongly bound to phosphate groups which does not freeze at low temperature and the other is weakly bound water freezing at 243-253 K. The distribution of correlation times has been stated for water in the first hydration shell of phosphate groups. For both acid and magnesium salt forms the hydration shell is composed of three water molecules.
Abstract:The translational mobility of polypropylenephosphate (PPP) molecules has been studied by the NMR pulsed field gradient technique. The translational diffusion of long chain polymer molecules of polymerization degree r~ > 20 may be neglected, in NMR measurements, on account of their rigidity. The self-diffusion coefficient of short chain polymer molecules (r~ = 8) in PPP gels (/)s = 3.10 -8 cm2/s) is about two orders of magnitude lower than that of water molecules in gels.
Hydration of the dimethylphosphate anion (DMP-) and dimethylphosphoric acid (DMPH) and of DMP-in the presence of a proton has been studied by the C N D 0 / 2 molecular-orbital method. The hydration energies of the (DMP--H,O) and ( DMPH-H20) complexes and the stabilization energies of ( DMP-.H+-H20) systems of different structures have been found, and additionally Wiberg indices and bond energies (together with their three components) have been computed. Regardless of the type of structure considered, for the trihydrate of dimethylphosphate in the presence of a proton only one water molecule in the first hydration shell is characterized by the lowest bond energy, which is about twice as low as energies of the two remaining water molecules. For the trihydrate of DMP-two water molecules at two equivalent positions, E , , and E3,, are characterized by the lowest hydrogenbond energy and are CQ. 20 kcalmol-' lower in energy than the most stable sites in acid structures. The results of theoretical studies support the experimental data obtained in investigations of the hydration of synthetic poly( dialkylphosphate) by the pulsed n.m.r. method. c v, h) P
Abstract:The structure and properties of bound water, nonfreezing at low temperature, in polypropylenephosphate (PPP) gels have been studied by the pulsed Fourier transform NMR method. The amount of hydrate water in gels depends strongly on the type of counterions. For PPP in acid and magnesium salt forms this amount was found to be three and eight moles per one mole of phosphate groups, respectively. The shape of a resonance line of bound water protons at low temperature was approximated by the curve of the system of proton pairs of statistically distributed orientations. The distance between two interacting protons in a pair, calculated from NMR spectrum, corresponds to the H-H distance in an isolated water molecule. This means that hydrate water molecules are fixed at hydration sites of polymer phosphate groups at a distance limiting intermolecular proton-proton interaction. The analysis of the NMR signal shape confirms thatthe structures of the primary hydration layer of phosphodiester groups, proposed in our previous theoretical studies, exist in PPP gels.
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