Peculiarities in the physico-chemical behaviour of non-statistically substituted carboxymethylcelluloses

A characteristic feature of sodium carboxymethylcellulose (NaCMC) samples synthesized via an NaOH-induced phase separation process is the almost complete substitution in O-6 position and the significantly higher content of tricarboxymethylated units, leading to a small increase of the acidity constant. SEC/MALLS/DRI measurements of the NaCMC samples show a trimodal curve, including a high molar-mass peak which can be attributed to aggregates or associates of different geometries and high density. With regard to the polyelectrolyte complex formation process, these more compact aggregate structures cause the formation of more compact polyelectrolyte complexes with significantly smaller dimensions and higher particle density. Consequently, ordered polyelectrolyte complex structures appear. Furthermore, this type of unconventionally substituted NaCMC sample can be put to good use for stabilizing colloidal dispersions, e.g. colloidal BaSO4. Due to the good adsorption of the NaCMC sample onto the colloidal particle surface, multiple polyanion-polycation coating layer-by-layer becomes possible. (C) 2001 Published by Elsevier Science B.V. All rights reserved.