Fluorescence and ESR studies of the conformational behavior of oppositely charged polyelectrolytes at solid/liquid interfaces

Kramer, Claudia; Somasundaran, P.

doi:10.1016/j.jcis.2004.01.009

Cited by 6 publications

(3 citation statements)

References 34 publications

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“…Lack of chromophores in natural biopolymers, strong scattering by the coacervate phase, and the dynamic nature of the condensation of the polymers to varied sizes of liquid droplets further aggravate these difficulties. There have been reports in the literature on the attempts to study the coacervate chain dynamics by techniques including NMR, ESR, fluorescence, FRAP, and various scattering techniques, − which has led to the understanding of kinetics of polyelectrolyte complexation. There have also been attempts to introduce improved techniques like X-ray reflectivity, diffusion wave spectroscopy, and confocal scanning laser microscopy for investigating coacervation. , Nonetheless, the fundamental structure-dynamic properties of complex coacervates especially with regards to solvent dynamics within coacervates remain poorly quantified.…”

Section: Introductionmentioning

confidence: 99%

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced ¹H NMR

et al. 2009

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We present the first study of quantifying the diffusion coefficient of interfacial water on polyelectrolyte surfaces of systems fully dispersed in bulk water under ambient conditions. Such measurements were made possible through the implementation of a recently introduced Dynamic Nuclear Polarization (DNP) technique to selectively amplify the nuclear magnetic resonance (NMR) signal of hydration water that is interacting with specifically located spin labels on polyelectrolyte surfaces. The merit of this novel capability is demonstrated in this report through the measurement of solvent microvisosity on the surface of two types of oppositely charged polyelectrolytes, when freely dissolved versus when complexed to form a liquid-liquid colloidal phase called complex coacervates. These complex coacervates were formed through electrostatic complexation between the imidazole-based cationic homopolymer poly(N-vinylimidazole) (PVIm), and anionic polypeptide polyaspartate (PAsp) in the pH range of 4.5 -6.0, under which conditions the coacervate droplets are highly fluidic yet densely packed with polyelectrolytes. We also investigated the rotational diffusion coefficients of the spin labels covalently bound to the polyelectrolyte chains for both PVIm and PAsp, showing a 5 fold change in the rotational correlation time as well as anisotropy parameter upon coacervation, which represents a surprisingly small decrease given the high polymer concentration inside the dense microdroplets. For both DNP and ESR experiments, the polymers were covalently tagged with stable nitroxide radical spin labels (∼1 wt %) to probe the local solvent and polymer segment dynamics. We found that the surface water diffusion coefficients near uncomplexed PVIm and PAsp at pH 8 differ, and are around D∼1.3×10 −9 m 2 / s. In contrast, inside the complex coacervate phase, the water diffusion coefficient in the immediate vicinity of either polyelectrolyte was D∼ 0.25×10 −9 m 2 / s, which is about an order of magnitude smaller than the bulk water self diffusion coefficient, and yet orders of magnitude greater than that of associated, bound, hydration water. This observation suggests the existence of measurable water inside complex coacervates with relatively high diffusion and exchange dynamics, implying that water moves in nanometer-scale pore spaces as opposed to being structurally bound or even absent. We infer from our observation that the PVIm and PAsp chains are undergoing roughly pairwise association, so that largely charge neutralized species compose the concentrated, yet fluidic and partially hydrated coacervate cores.

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Section: Introductionmentioning

confidence: 99%

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced ¹H NMR

et al. 2009

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“…In fact, nitroxides are known to exhibit ESR spectra that depend on the mobility of the spin-probe and the microviscosity of the probe environment. They have been used to evaluate the microstructure of the absorbed layer of surfactants and polymers at the solid-liquid interface [11][12][13][14][15] and also inside composite polymers [16,17]. In this study a small nitroxide such as TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) and two nitroxide labeled fatty acids (5-and 16-doxyl stearic acids) were used; it is assumed that the polar head groups of the probe molecules (nitroxide group for TEMPO and carboxylic groups for fatty acids) tend to be positioned on the surface of the calcium carbonate cores.…”

Section: Introductionmentioning

confidence: 99%

Spin-probe ESR and molecular modeling studies on calcium carbonate dispersions in overbased detergent additives

Montanari

Frigerio

2010

Journal of Colloid and Interface Science

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“…In fact, nitroxides are known to exhibit ESR spectra that depend on the mobility of the spin-probe and the micro-viscosity of the probe environment. They have been used to evaluate the microstructure of the absorbed layer of surfactants and polymers at the solid-liquid interface [10][11][12][13][14] and also inside composite polymers [15,16].…”

Section: Introductionmentioning

confidence: 99%

Characterisation of the Surfactant Shell Stabilising Calcium Carbonate Dispersions in Overbased Detergent Additives: Molecular Modelling and Spin-Probe-ESR Studies

Frigerio

Montanari

2007

Computational Science – ICCS 2007

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Abstract. The surfactant shell stabilising the calcium cabonate core in overbased detergent additives of lubricant base oils was characterised by computational and experimental methods, comprising classical force-field based molecular simulations and spin-probe Electron Spin Resonance spectroscopy. An atomistic model is proposed for the detergents micelle structure. The dynamical behaviour observed during diffusion simulations of three nitroxide spin-probe molecules into micelle models could be correlated to their mobility as determined from ESR spectra analysis. The molecular mobility was found to be dependent on the chemical nature of the surfactants in the micelle external shell.

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Fluorescence and ESR studies of the conformational behavior of oppositely charged polyelectrolytes at solid/liquid interfaces

Cited by 6 publications

References 34 publications

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced ¹H NMR

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced ¹H NMR

Spin-probe ESR and molecular modeling studies on calcium carbonate dispersions in overbased detergent additives

Characterisation of the Surfactant Shell Stabilising Calcium Carbonate Dispersions in Overbased Detergent Additives: Molecular Modelling and Spin-Probe-ESR Studies

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Fluorescence and ESR studies of the conformational behavior of oppositely charged polyelectrolytes at solid/liquid interfaces

Cited by 6 publications

References 34 publications

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced 1H NMR

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced 1H NMR

Spin-probe ESR and molecular modeling studies on calcium carbonate dispersions in overbased detergent additives

Characterisation of the Surfactant Shell Stabilising Calcium Carbonate Dispersions in Overbased Detergent Additives: Molecular Modelling and Spin-Probe-ESR Studies

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Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced ¹H NMR

Local Water Dynamics in Coacervated Polyelectrolytes Monitored through Dynamic Nuclear Polarization-Enhanced ¹H NMR