A nuclear magnetic resonance study on the conformation and molecular interaction of polyelectrolyte model compound in alcohol/water mixtures

Abstract

The conformation and molecular interaction of polyelectrolyte model compound (2,4-dimethylglutaric acid) in alcohol/water mixtures were investigated by using high resolution NMR spectroscopy.I t is shown that the local conformation of mesa-isomer in alcohol/water mixtures slightly changes with the mole fraction of ethanol. The difference in the chemical shifts of two methylene protons and the chemical shift of carboxyl protons are comparably dependent of the mole fraction of ethanol. These results, however, do not always mean that the change in the viscosity of poly(acry1ic acid) or poly(methacry1ic acid) in alcohol/water mixtures is due to the change of such local conformation as estimated by NMR. On the contrary, it is probably true that such change in the viscosity curve is mainly due to the long-range interaction between non-adjacent segments.It is also shown that the local conformation of mesa-isomer depends upon the use of the solvents, leading to the conclcsion that its local conformation varies with the solvent. ZUSAMMENFASSUNG:Konformation und molekulare Wechselwirkung der Modellverbindung eines Polyelektrolyten (2,4-Dimethylglutarsaure) in Alkohol/Wasser-Gemischen wurden mittels hochauflosender Kernresonanz untersucht.Es wurde gezeigt, daB sich die lokale Konformation der mesomeren 2,4-Dimethylglutarsaure in Alkohol/Wasser-Gemischen mit dem Molenbruch des dthanols leicht andert. Der Unterschied der chemischen Verschiebungen der beiden Methylenprotonen und die Verschiebung der Carboxylprotonen sind in vergleichbarem MaBe vom Molenbruch des dthanols abhangig. Diese Ergebnisse lassen jedoch nicht den SchluR zu, daB die Viskositatsanderungen van Polyacrylsaure oder Polymethacrylsaure in Alkohol/Wasser-Gemischen auf die durch die NMR-Daten belegten dnderungen lokaler Konformationen zuriickzufiihren sind. Tatsachlich diirfte der Gang der Viskositatskurve hauptsachlich auf die weitreichende Ketten-Wechselwirkung nicht benachbarter Segmente zuriickzufuhren sein.Es konnte gleichzeitig gezeigt werden, daB die lokale Konformation der mesomeren 2,4-Dimethylglutarsaure vom Losungsmittel abhangt. Dies legt den SchluR nahe, daB sich die lokale Konformation mit dem Losungsmittel andert.

Evolution of Hydrogen-Bond Interactions within Single Levitated Metastable Aerosols Studied by In Situ Raman Spectroscopy

“…This divergence in correlated intermolecular behavior may give rise to the orders of magnitudes lower viscosity of CA compared to the sucrose. NMR studies on the viscosity of organic acids in the alcohol/water system support this hypothesis by reporting that the change in viscosity is due to the long-range interaction between the nonadjacent molecular segments . Strong long-range interactions mentioned in this study may correspond to the network-like liquid structure of the sucrose droplet.…”

“…NMR studies on the viscosity of organic acids in the alcohol/water system support this hypothesis by reporting that the change in viscosity is due to the long-range interaction between the nonadjacent molecular segments. 70 Strong long-range interactions mentioned in this study may correspond to the network-like liquid structure of the sucrose droplet. The viscosity of OAs is analyzed and predicted using the O/C ratio or the types and the number of the functional groups of the organic molecules.…”

Raman spectroscopic study of hydrogen bonding in aqueous carboxylic acid solutions. 3. Polyacrylic acid

“…The physical properties of aqueous polyacrylic acid solutions were studied by various methods. [1][2][3][4][5][6][7] The intrinsic viscosity of polyacrylic acid in alcohol/water mixtures1 indicated that the hydrogen bond between carboxyl groups affected the conformation in alcohol/water mixtures. Miyamoto and Cantow2 investigated the effect of solvents upon the conformation of meso and racemic 2,4-dimethylglutaric acids, model compounds of polyacrylic acid, by using high-resolution 1H NMR spectroscopy.…”