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Structure of the polymers studied: hydroxyethylcellulose (HEC) and cationic HEC (cat-HEC) polymers. In HEC, R = H or -(CH2CH2O)nH while for cat-HEC, R = H, -(CH2CH2O)nH, or -(CH2CH2O)nCH2(CH2OH)CH2N + (CH3)3Cl−
Source publication
NMR solvent relaxation has been used to characterize the surfaces present in binary anionic particle dispersions, before and after exposure to a cationic polymer. In the polymer-free case, it is shown that the measured specific relaxation rate of the solvent is a population-weighted average of all surfaces present, enabling preferential adsorption...
Contexts in source publication
Context 1
... (HEC) is a partially substituted hydroxyethyl ether of cellulose. Each hydroxyethyl group can be further derivatized by reacting with ethylene oxide to form a side chain that may be subsequently quaternized i.e., ammonium salts of trimethylammonium derivatives of HEC (Figure 1), to yield cationic polymers whose charge is defined by the extent of charge modification through the degree of substitution expressed as 0.9%. Classified as polyquaternium-10, according to the International Nomenclature of Cosmetic Ingredients (INCI), this family of polymers is manufactured under the trade name UCARE (Dow Chemical Company, Midland, MI, USA). ...
Context 2
... SANS analysis [13] of the polymer indicated it exhibited a rodlike solution conformation with each unit within the rod exhibiting a dimension R = 0.8 nm and L = 1 nm i.e., volume = 2-3 nm 3 whilst analysis of its self-diffusion behavior14 indicates an effective hydrodynamic (spherical) radius of roughly 25 nm [14]. Ludox TM-50 (Sigma-Aldrich, St. Louis, MO, USA), titanium (IV) oxide, anatase (TiO2) (Sigma-Aldrich, St. Louis, MO, USA), Laponite-RD (Laponite) (BYK Additives and Instruments, Wesel, Germany) and styrene/acrylic latex dispersion [15], (AkzoNobel Figure 1. Structure of the polymers studied: hydroxyethylcellulose (HEC) and cationic HEC (cat-HEC) polymers. ...
Context 3
... experimental protocols were explored: (1) varying the total particle surface area with a constant ratio of the two particles ( σ silica σ secondary ) i.e., f n (σ silica + σ secondary ); or (2) varying the total particle surface area in the presence of a fixed amount of one of the two particles i.e., f n (σ silica ) + σ secondary . The solvent relaxation data are presented in compound Figure 1, for Ludox/latex (top row), Ludox/laponite (middle 2 rows) and Ludox/TiO 2 (bottom row), in terms of particle concentrations (left column) and surface areas (right column). ...
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... simple presentation of the data is to compare the initial and equilibrium mass fractions post-exposure to the polymer and following gentle centrifugation, Supplemental Figure S1, to quantify the amount of solid material that is rendered unstable. This analysis indicates that the polymer removes all the particles in 3 wt% Ludox and 3 wt% latex dispersions in the individual single particle systems, consistent with the similar ζ-potentials on the particles, and broadly similar amounts in their mixtures. ...
Context 5
... Materials: The following supporting information can be downloaded at: www.mdpi.com/xxx/s1, Figure S1: Pseudo-adsorption isotherm -the mass of particle removed from a series of Ludox-latex dispersions by gentle centrifugation after exposure to HEC LR at a concentration of 1000 ppm; Figure S2: Pseudo-adsorption isotherm -the mass of particle removed from a series of dispersions comprising silica (left) and Laponite (right) by gentle centrifugation after exposure to HEC LR at a concentration of 100 ppm.; Figure S3: Small-angle neutron scattering from Figure 8b presents analogous behavior-specific relaxation rates versus particle concentrations. For Ludox/TiO 2 blends in the presence of fixed concentrations of TiO 2 , again, post-centrifugation i.e., dispersions with an initial 0.2 wt% TiO 2 fixed concentration plus varying Ludox, post-centrifugation, result in an R 2sp . ...
Context 6
... Materials: The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/polym14091875/s1, Figure S1: Pseudo-adsorption isotherm-the mass of particle removed from a series of Ludox-latex dispersions by gentle centrifugation after exposure to HEC LR at a concentration of 1000 ppm; Figure S2: Pseudo-adsorption isotherm-the mass of particle removed from a series of dispersions comprising silica (left) and Laponite (right) by gentle centrifugation after exposure to HEC LR at a concentration of 100 ppm.; Figure S3: Smallangle neutron scattering from binary blends of Ludox/latex dispersions and a Ludox comparator to illustrate a lack of interparticle interaction or particle size fractionation. ...
Citations
... Previous relaxation NMR studies on Latex and Ludox particles have reported relaxation rate enhancement values of 0.24 wt% −1 and 0.50 wt% −1 for Ludox and Latex (4 wt% methacrylic acid stabilization), respectively [22,23]. Therefore, results reported here are in keeping with previous literature and highlight how the presence of acid groups on hydrophobic Latex particles can present relaxation rate enhancements greater than hydrophilic Ludox particles. ...
... Order of addition is known to play a key role in the adsorption behaviour of polymers and polymer-surfactant complexes onto particle surfaces [21,22,34,35]. This study aims to investigate the effect that charge ratio ( Previous relaxation NMR studies on Latex and Ludox particles have reported relaxation rate enhancement values of 0.24 wt% −1 and 0.50 wt% −1 for Ludox and Latex (4 wt% methacrylic acid stabilization), respectively [22,23]. Therefore, results reported here are in keeping with previous literature and highlight how the presence of acid groups on hydrophobic Latex particles can present relaxation rate enhancements greater than hydrophilic Ludox particles. ...
... Data are presented in terms of relaxation rate enhancements (R 2sp ) as a function of the equilibrium particle concentration, determined through dry weight analyses. Another simple presentation of the data is to compare the initial and equilibrium mass fractions post exposure to the oppositely charged polymer-surfactant complex and centrifugation protocol to quantify the amount of solid material that is rendered unstable [23]. Figure 3 shows these data for the mixtures containing cat-HEC polymer (n = 0.95%), SDS and Ludox. ...
This study investigates the flocculation induced destabilization of particulate dispersions by oppositely charged polymer–surfactant complexes, with a particular focus on controlling interactions by modulating the charge ratio Z, (where Z = [+polymer]/[−surfactant]) via [−surfactant] at fixed Cpolymer. Cationic hydroxyethyl cellulose (cat-HEC) polymer-sodium dodecylsulfate (SDS) complexes were prepared with either excess polymer (Z > 1) or surfactant (Z < 1) charges. Anionic particulate dispersions (Ludox and polystyrene-butadiene Latex) were then exposed to the complexes, and solvent relaxation NMR was used to characterize the particle surfaces before and after exposure. In both particulate dispersions, flocculation induced destabilization was enhanced after exposure to cat-HEC-SDS complexes with Z > 1, leaving any excess particle surfaces uncoated after gentle centrifugation. However, complexes with Z < 1 showed no adsorption and destabilization in the Ludox dispersions and only slight destabilization in the Latex dispersions due to possible hydrophobic interactions. Substituting SDS for non-ionic surfactant (C12E6) showed no additional destabilization of the dispersions, but post-centrifugation relaxation rates indicated preferential adsorption of C12E6 onto the particle surfaces. Since the dominant forces are electrostatic, this study highlights the possibility of controlling the interactions between oppositely charged polymer–surfactant complexes and particle surfaces by modulating Z through [−surfactant].
With applications across chemistry, physics and medicine, nuclear magnetic resonance is a proven, uniquely versatile and powerful spectroscopic technique. The success of NMR and its constant redevelopment means that the literature is vast and wide-ranging. Each chapter in this volume is a distillation of the key recent literature in different areas, covering the spectrum of NMR theory and practice, and including theory and computation of nuclear shielding, NMR of soft matter, hyperpolarisation techniques and NMR of living systems. These reports are invaluable both for new researchers wishing to engage with literature for the first time, and for seasoned practitioners, particularly service managers, needing to keep in touch with the ever-expanding ways in which NMR is used.
With applications across chemistry, physics and medicine, nuclear magnetic resonance is a proven, uniquely versatile and powerful spectroscopic technique. The success of NMR and its constant redevelopment means that the literature is vast and wide-ranging. Each chapter in this volume is a distillation of the key recent literature in different areas, covering the spectrum of NMR theory and practice, and including theory and computation of nuclear shielding, NMR of soft matter, hyperpolarisation techniques and NMR of living systems. These reports are invaluable both for new researchers wishing to engage with literature for the first time, and for seasoned practitioners, particularly service managers, needing to keep in touch with the ever-expanding ways in which NMR is used.
