Hydration of synthetic polypropylenephosphate (PPP) ? a simplified model for natural teichoic acids Part 3. Bound (nonfreezing) water in PPP gels by the pulsed Fourier transform NMR method

Abstract

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.

Polymers with Esters of Phosphoric Acid Units: From Synthesis, Models of Biopolymers to PolymerInorganic Hybrids

“…The translational motions of water in poly(trimethylene phosphate) ( 13 ) gels has been studied by the NMR pulsed field gradient technique 61–63. In polymer gels there are two phases of water with different translational mobility.…”

“…The distance between two interacting protons in a pair, calculated by NMR spectroscopy, 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 interactions 63. The mobility of water is depressed much more effectively in the presence of magnesium ions than in the case of hydrogen ions 62…”