PHASE-BEHAVIOR OF THE TERNARY-SYSTEM WATER HYDROXYETHYL CELLULOSE/NONIONIC SURFACTANT/

The phase behavior of ternary aqueous solutions of two samples of hydr oxyethyl cellulose (HEC) and oligoethylene glycol mono(n-alkyl) ethers C(x)E(y) (x: 11; y: 28, 40) at 25 degrees C has been studied above th e CMC of C(x)E(y). The influence of molar mass of HEC and the number o f ethylene glycol units on the phase diagram has been investigated. Bo th binary systems water/HEC and water/C(x)E(y) are completely miscible . The ternary mixture of water/polymer/nonionic surfactant is homogene ous if the weight fraction of water is larger than 0.93, or else it ca n separate segregatively, i.e., HEC is enriched in one phase, the surf actant in the other. The theoretical description is based on an equati on for the Gibbs energy of mixing which takes polar conformations into account. The phase diagrams are calculated by means of a new method w hich does not require the derivatives of the Gibbs energy of mixing.