Phase equilibria and interfacial tension between coexisting phases for the system water/2-propanol/poly(acrylic acid)
✍ Scribed by Zhen Tong; Kristin Meissner; B. A. Wolf
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 351 KB
- Volume
- 196
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
The cloud point curve, tie‐lines and interfacial tensions were measured for solutions of 50 mol‐% neutralized (counter‐ion Na^⊕^) poly(arylic acid) (mass‐average molar mass M̄~w~ = 9700 g/mol; polydispersity index M̄~w~/M̄~n~ = 2,0) in the mixed solvent water/2‐propanol at 30°C. Due to the non‐uniformity of the polymer, the end‐points of the tie‐lines are not situated on the cloud‐point curve. The interfacial tension σ — determined by means of the spinning drop method — increases in sigmoidal manner with R~tl~, the length of the tie‐line, expressed in terms of weight fractions. An evaluation of these data in a double‐logarithmic plot of σ · M^−0,5^ versus R~tl~ yields a critical exponent of 4,23 as compared with 3,85 in the case of binary systems. The dependence of σ on w~w~, the over‐all weight fraction of water in the mixture, can also be expressed as a power‐law choosing (w~cw~−w~w~)/w~cw~ as the concentration variable (w~cw~: critical weight fraction of water); for the present system the exponent of the resulting equation amounts to 2,33 as compared with 2,0 for toluene/polyisobutylene/poly(dimethylsiloxane).