Effects of Hydroxyl Groups in Organic Ammonium Counterions on the Properties of Fluorinated Surfactants

The surface tension, foaming and viscosity for C_7F_(15)COO^-N^+H(C_2H_4OH)_x(C_2H_5)_(3-x) and C_8F_(17)SO_3^-N^+H(C_2H_4OH)_x(C_2H_5)_(3-x)(x=0, 1,2, 3) were measured to systematically study the effects of hydroxyl groups in organic ammonium counterions on the properties of perfluorooctanoates and perfluorooctanesulfonates. The results showed that the critical micelle concentration (cmc) and the surface tension at cmc (γ_(cmc)) were both increased with the increase of number of hydroxyl groups (x) in the two series. The perfluorooctanesulfonate had smaller cmc but higherγ_(cmc) than perfluorooctanoate with the same counterion. The minimum molecular area of surface adsorption (A_(min)) of C_8F_(17)SO_3^-N^+H(C_2H_4OH)_x(C_2H_5)_(3-x) were 0.64, 0.57, 0.63 and 0.72 nm^2 while the A_(min) values of C_7F_(15)COO^-N^+H(C_2H_4OH)_x(C_2H_5)_(3-x) were 0.61, 0.62, 0.61 and 0.71 nm_2 when x=0, 1, 2 and 3,respectively. For the investigated systems of surfactants, the results of foam expansion ratio agreed with those of surface activity, while the 25% drainage time were consistent with the results of viscosity.

The surface tension, foaming and viscosity for C7F15COO^-N^＋H（C2H4OH）χ（C2Hs）3-x and C8F17SO3- N^＋H（C2H4OH）χ（C2H5）3-χ （x = 0, 1, 2, 3） were measured to systematically study the effects of hydroxyl groups in organic ammonium counterions on the properties of perfluorooctanoates and perfluorooctanesulfonates. The results showed that the critical micelle concentration （cmc） and the surface tension at cmc （γcmc） were both increased with the increase of number of hydroxyl groups （χ） in the two series. The perfluorooctanesulfonate had smaller cmc but higher γ=cmc than perfluorooctanoate with the same counterion. The minimum molecular area of surface adsorption （Amin） of C8F17zSO3^-N^＋H（C2H4OH）χ（C2H5）3-χ were 0.64, 0.57, 0.63 and 0.72 nm^2 while the Amin values of C7F15COO^-N^＋H（C2H4OH）χ（C2H5）3-χ were 0.61, 0.62, 0.61 and 0.71 nm^2 when χ = 0, 1, 2 and 3, respectively. For the investigated systems of surfactants, the results of foam expansion ratio agreed with those of surface activity, while the 25% drainage time were consistent with the results of viscosity.