A series of unexpected thermo-responsive phenomena were discovered in an aqueous solution of the cationic gemini surfactant, 2-hydroxypropyl-1,3-bis(alkyldimethylammonium chloride) (n-3(OH)-n(2Cl), n = 14, 16), in the presence of an inorganic salt. The viscosity change trend for the 14-3(OH)-14(2Cl) system was investigated in the 20-40 °C temperature range. As the temperature increased, the viscosity of the solution first decreased to a minimum point corresponding to 27 °C, and then increased until a maximum was reached, after which the viscosity decreased again.
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