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Phase equilibria and interfacial tension between coexisting phases for the system water/2‐propanol/poly(acrylic acid)
Author(s) -
Tong Zhen,
Meissner Kristin,
Wolf B. A.
Publication year - 1995
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1995.021960208
Subject(s) - binodal , molar mass , mass fraction , dispersity , surface tension , cloud point , chemistry , drop (telecommunication) , thermodynamics , phase (matter) , polymer chemistry , analytical chemistry (journal) , lower critical solution temperature , polymer , chromatography , physics , phase diagram , organic chemistry , aqueous solution , copolymer , telecommunications , computer science
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).