Characterization of Sodium Carboxymethyl Cellulose Aqueous Solutions to Support Complex Product Formulation: A Rheology and Light Scattering Study (original) (raw)
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Structure of sodium carboxymethyl cellulose aqueous solutions: A SANS and rheology study
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The linear dynamic viscoelastic properties and non-linear transient rheology of sodium carboxymethylcellulose solutions (Na-CMC) in propylene glycol/water mixtures were investigated. Measurements were carried out for the solutions of Na-CMC with three different degrees of substitution (DS), namely 0.62, 0.79, 1.04, and the similar average molecular weight (M w & 250,000 g/mol). The strong synergism between the molecules of Na-CMC with DS of 0.62 and 0.79, and propylene glycol has been observed. The occurrence of the overshoot shear stress and the low loss tangent values indicate the physical cross-linking of the polymer chains. The increase of propylene glycol concentration over 80 wt% and sodium carboxymethylcellulose (DS = 0.7) over 1.6 wt% leads to the formation of a physical cross-link network. The absence of overshoot shear stress and terminal behaviour in SAOS flow of the Na-CMC 1.04 solutions in the PG/water mixture shows that no intermolecular cross-linking of polymer chains occurred in them.
Biomacromolecules, 2007
Two model sodium carboxymethyl celluloses (CMC) with similar monomer composition but with significant differences in the viscoelastic properties, that could not be assigned to variations in the average molar mass or molar mass distribution, were investigated with respect to the fraction of nonsubstituted cellulose segments in the polymers. The CMCs were hydrolyzed by a purified highly selective endoglucanase. The average molar mass and molar mass distribution of the enzyme products, as measured by size-exclusion chromatography with online multi-angle light scattering and refractive index detection (SEC/MALS/RI), revealed that the enzyme-catalyzed hydrolysis was more effective on one of the CMCs. To investigate whether this was due to a higher fraction of nonsubstituted cellulose segments in the polymer, the concentrations of nonsubstituted enzyme products, e.g., cellotetraose and cellopentaose, were measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). It was concluded that the two CMCs displayed significant differences in the fraction of nonsubstituted cellulose segments. Furthermore, the CMC with the strongest attractive intermolecular interactions, according to rheometry, also contained the highest fraction of nonsubstituted cellulose segments.
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The Canadian Journal of Chemical Engineering, 2016
Non-Newtonian flow behaviours of dilute and semi-dilute carboxymethyl cellulose (CMC) solutions in the presence of spindle-shaped cellulose nanocrystal particles (CNC) were investigated. Scanning transmission electron microscopy, dynamic light scattering, polarized optical microscopy, and turbidity measurements of CNC suspensions in CMC solutions were also carried out. Adding CNC particles only within the range of 0.33-2.0 m 3 /m 3 into the dilute and semi-dilute CMC polymer solutions increased the viscosities at low shear rates between 10 3-10 5 times. The flow curves of CNC suspensions in CMC polymer solutions turned highly non-Newtonian, and their viscosities at high shear rates (> 10 3) still converged to the flow curves of CMC solutions. The viscosity increase comes from the nematic flocculation of CNC particles in the presence of a non-adsorbing CMC polymer which results in CNC flocs with water entrapped pockets.