Effects of Compressed Carbon Dioxide on the Phase Equilibrium and Molecular Order of a Lyotropic Polyamide Solution

• Published in: Macromolecules Vol. 29; no. 14; pp. 4904 - 4909
• Main Authors: Winters, Michael A, Debenedetti, Pablo G, Condo, Peter D, Radosz, Maciej, Schmidt, Hans-Werner
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.07.1996
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; Non solvent; Nylon; Ternary system; Phase diagram; Aromatic polymer; Liquid carbon dioxide; Mesomorphic state structure; Experimental study; Liquid crystals; Pressure effect; Chlorine containing polymer; Lyotropic state; Concentrated solution
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma9518518

The effects of compressed carbon dioxide at slightly subcritical temperatures on solutions of a chloro-substituted, para-linked aromatic polyamide (PPTA-Cl) in dimethylacetamide were investigated by depolarized light spectroscopy. Pressurization of isotropic solutions resulted in polymer precipitation at a sharply defined pressure. Pressurization of nematic solutions resulted in an increase in the intensity of scattered light with no evidence of precipitation. A plausible interpretation of this observation is the occurrence of liquid−liquid phase separation into polymer-rich (anisotropic) and polymer-lean (isotropic) phases induced by the compressed carbon dioxide. The results suggest that compressed, near-critical antisolvents can be used to control the degree of anisotropy in liquid-crystalline polymeric systems.