Patterns of phase behavior in polymer and amphiphile mixtures

A relatively unexplored area of research, the phase behavior of amphiphile and polymer mixtures in water is examined as a function of temperature and composition. The miscibility of ethoxylated alcohol amphiphile [CH₃(CH₂)_i-1O(CH₂CH₂O)_jH] and poly(ethylene oxide) in water decreases strongly upon increasing the strength of the amphiphile (i + j) or increasing the molecular weight of the polymer. As the amphiphile is stretched from the weakly associating C₄E₁ to the micelle-forming surfactant C₈E₄, the separate upper and lower miscibility gaps of C₄E₁/polymer/water collide and merge to form a continuous two-phase region from low to high temperatures. A similar trend is observed upon increasing polymer molecular weight. Some of the phase behavior patterns resemble those found for mixtures of two polymers in a solvent.