Salinity hydrophobically associating polymer

Chen, H., Zhang, S.H., Chu, Y.B., Yang, H.X., Liu, F.L., 2004. Development and application of hydrophobically associating polymer gel in high-temperature and high-salinity reservoirs for profile modification. Oilfield Chemistry 21 (4), 343-346. 

The effect of monovalent and divalent salts on the solubility of these hydrophobically associating polymers (HAPs) is similar to that of ionic surfactants. An increase in salt content decreases solubility. With increasing salinity, the hydrocarbon chains are forced into closer proximity to the point where the subtle balance between hydrophobic associative forces and hydrophilic hydration forces breaks down, and phase separation results. Divalent cations have a larger effect on decreasing polymer solubility than do alkaline earth or monovalent cations. This is particularly so when the polymer contains anionic functionality such as acrylate or sulfonate. Another interesting phenomena occurs in mixed salts with certain polymer compositions when the ratio of divalent to monovalent cation is varied. A window of solubility is observed similar to that found with anionic surfactant solutions. 

Li, H.-R, Zhao, H.T., Zhao, P.C., Chen, H., 2006b. Laboratory study of hydrophobically-associ-ating-polymer-based gel as a profiling agent in high-temperature and high-salinity Zhongyuan oil fields. Oilfield Chemistry 23 (1), 50-53. 

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