Viscosity and scaling of semiflexible polyelectrolyte NaCMC in aqueous salt solutions

Carlos G. Lopez, Ralph H. Colby, Peter Graham, Joao T. Cabral

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

We investigate the viscosity dependence on concentration and molecular weight of semiflexible polyelectrolyte sodium carboxymethylcellulose (NaCMC) in aqueous salt-free and NaCl solutions. Combining new measurements and extensive literature data, we establish relevant power laws and crossovers over a wide range of degree of polymerization (N) as well as polymer (c) and salt (cs) concentrations. In salt-free solution, the overlap concentration shows the expected c ∝ N-2 dependence, and the entanglement crossover scales as ce ∝ N-0.6±0.3, in strong disagreement with scaling theory for which ce ∝ c is expected, but matching the behavior found for flexible polyelectrolytes. A second crossover, to a steep concentration dependence for specific viscosity (ηsp ∝ c3.5±0.2), commonly assigned to the concentrated regime, is shown to follow c ∝ N-0. ±0.2 (with c/ce 〈 6) which thus suggests instead a dynamic crossover, possibly related to entanglement. The scaling of c and ce in 0.01 and 0.1 M NaCl shows neutral polymer in good solvent behavior, characteristic of highly screened polyelectrolyte solutions. This unified scaling picture enables the estimation of viscosity of ubiquitous NaCMC solutions as a function of N, c, and cs and establishes the behavior expected for a range of semiflexible polyelectrolyte solutions.

Original languageEnglish (US)
Pages (from-to)332-338
Number of pages7
JournalMacromolecules
Volume50
Issue number1
DOIs
StatePublished - 2017

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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