Phase behavior of (polyacrylamides + water) solutions: concentration, pressure ...

• Author(s): Azevedo, R. Gomes de ; Rebelo, L. P. N. ; Ramos, A. M. ; Szydlowski, J. ; Sousa, H. C. de ; Klein, J.
• Date: 2001
• Persistent ID: http://hdl.handle.net/10316/3827
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Liquid-liquid equilibria; Polyacrylamides; Polymeric aqueous solutions; Pressure effects; Isotope effects
• Document Type: Article
• Language: English

Description

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 20 wt.%. In the case of copoly(PNIPAAM/vinylsaccharide) several different chain lengths were considered. Pressure (up to 400 bar) 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. http://www.sciencedirect.com/science/article/B6TG2-43MC9F5-N/1/63fb7dd8bec4ff798723b9bcb318a0a5