6533b7ddfe1ef96bd12747d2

RESEARCH PRODUCT

Phase equilibria and interfacial tension between coexisting phases for the system water/2-propanol/poly(acrylic acid)

subject

description

The cloud point curve, tie-lines and interfacial tensions were measured for solutions of 50 mol-% neutralized (counter-ion Na ○+ ) poly(acrylic acid) (molar mass M w = 9 700 g/mol; polydispersity index M w /M 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 overall weight fraction of water in the mixture, can also be expressed as a powerlaw 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)