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

• Autor(a) principal: Azevedo, R. Gomes de
• Data de Publicação: 2001
• Outros Autores: Rebelo, L. P. N., Ramos, A. M., Szydlowski, J., Sousa, H. C. de, Klein, J.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10316/3827; https://doi.org/10.1016/s0378-3812(01)00469-1
• topic: Liquid-liquid equilibria; Polyacrylamides; Polymeric aqueous solutions; Pressure effects; Isotope effects

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.