Dresden 2017 – wissenschaftliches Programm
CPP 51.9: Poster
Mittwoch, 22. März 2017, 18:30–21:00, P3
Scaling laws and solution rheology of semiflexible polyelectrolyte carboxymethyl cellulose: influence of electrostatic and hydrophobic interactions — •Carlos Lopez1, Peter Graham2, Ralph Colby3, and Joao Cabral1 — 1Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom — 2Unilever Research Port Sunlight Laboratory, Quarry Road East, Bebington L63 3JW, United Kingdom — 3Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
We investigate the conformation and rheology of sodium carboxymethyl cellulose (NaCMC) solutions. Scaling laws for the overlap and entanglement concentrations are established in salt free, NaCl and NaOH solutions. NaCl screens electrostatic interactions but not hydrophobic ones, while NaOH screens both. In salt free and NaCl solution, a highly substituted sample displays typical polyelectrolyte and neutral polymer in good solvent behaviour respectively. The viscosities in NaOH solutions are similar to those in NaCl. Less substituted samples display hydrophobic behaviour in salt free and NaCl solution, becoming thixotropic gels at high concentrations. However, the viscosities in NaOH are identical to those of the more substituted sample due to solubilisation of unsubstituted cellulose patches.
By varying the ionic strength and pH of aqueous solutions, it is possible to tune the polymer-solvent interactions for NaCMC samples. This allows us to separate the effects of entanglements, electrostatic and hydrophobic interactions on the solution rheology of NaCMC.