Structure of Sodium Carboxymethyl Cellulose Aqueous Solutions: A SANS and Rheology Study

We report a small angle neutron scattering (SANS) and rheology study of cellulose derivative polyelectrolyte sodium carboxymethyl cellulose with a degree of substitution of 1.2. Using SANS, we establish that this polymer is molecularly dissolved in water with a locally stiff conformation with a stretching parameter B similar or equal to 1.06. We determine the cross sectional radius of the chain (r(p) similar or equal to 3.4 angstrom) and the scaling of the correlation length with concentration (xi = 296 c(-1/2)angstrom for c in g/L) is found to remain unchanged from the semidilute to concentrated crossover as identified by rheology. Viscosity measurements are found to be in qualitative agreement with scaling theory predictions for flexible polyelectrolytes exhibiting semidilute unentangled and entangled regimes, followed by what appears to be a crossover to neutral polymer concentration dependence of viscosity at high concentrations. Yet those higher concentrations, in the concentrated regime defined by rheology, still exhibit a peak in the scattering function that indicates a correlation length that continues to scale as c(-1/2). (C) 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc.