Rheological investigation on dynamic and structure of separated phases in polymer mixture–ionic surfactant ternary system

Ternary systems composed of 0.30% sodium carboxymethyl cellulose (NaCMC), 0.70% hydroxypropylmethyl cellulose (HPMC), and sodium dodecylsulfate (SDS) of various concentrations (0.00–2.00%), were investigated by oscillatory and flow shear rheometry. The investigation on binary mixtures of HPMC/SDS (0.7% HPMC, 0.00–2.00% SDS) and HPMC/NaCMC (1.00% polymer mixtures with HPMC/NaCMC mass ratio ranging from 1/0 to 0/1) was also carried out. In the examined systems, various interactions between HPMC–NaCMC, HPMC–SDS and NaCMC–(HPMC–SDS) take place. The interactions may bring about phase separation in the ternary system into HPMC–SDS complex rich phase (coacervate), and NaCMC rich phase (supernatant). The possibility of employing the interactions in the ternary system to vary structural properties of the coacervate, in terms of viscoelasticity and shear rate influence, was investigated. Rheological properties of the ternary system, as well as of the separated coacervate and the supernatant were tested. Influence of shear rate on the interactions taking place in both the binary and the ternary mixtures was examined. It was found that the applied shear rate can influence the interactions. Molecular mechanisms determining the rheological properties of the coacervate were suggested. It was found that complex intermolecular interactions in the ternary system can be employed to attain control over the structural properties of the coacervate phase.