Phase behavior of (polyacrylamides + water) solutions: concentration, pressure and isotope effects

R. Gomes de Azevedo, L. P. N. Rebelo, A. M. Ramos, J. Szydlowski, H. C. De Sousa, J. Klein

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75 Citations (Scopus)


Phase diagrams of poly(N-isopropylacrylamide) (PNIPAAM) as well as of hydrophilically-modified copolymers in aqueous solution were determined. A high-accuracy He-Ne Laser scattering technique was used for the detection of operational spinodal (sp) and cloud-point (cp) curves. Polymer concentration was varied from 0.5 to 20wt.%. In the case of copoly(PNIPAAM/vinylsaccharide) several different chain lengths were considered. Pressure (up to 400bar) and solvent isotope effects were studied. We predict a closed-loop type phase diagram for the copolymers, which presents an estimated hypercritical point in H2O solutions at Mw∼0.5×105, although only lower critical solution temperature (LCST) is experimentally accessible. At lower molecular weights, the solutions are always in the one-phase region.

Original languageEnglish
Pages (from-to)189-198
Number of pages10
JournalFluid Phase Equilibria
Issue number1-2
Publication statusPublished - 30 Jul 2001
Event14th Symposium on Thermophysical Properties - Boulder, United States
Duration: 25 Jun 200030 Jun 2000


  • Data
  • Isotope effects
  • Liquid-liquid equilibria
  • Polyacrylamides
  • Polymeric aqueous solutions
  • Pressure effects


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