全氟辛酸、全氟辛基磺酸乙醇胺盐表面活性剂的性质研究

通过测试表面张力、泡沫性质与粘度性质,研究全氟辛酸乙醇铵/二乙醇铵/三乙醇铵和全氟辛基磺酸乙醇铵/二乙醇铵/三乙醇铵的性质。实验表明,反离子对全氟辛酸盐和全氟辛基磺酸盐表现出相同规律的影响,这种影响体现在反离子的疏水性和空间体积两个方面,分别导致了cmc顺序:乙醇铵二乙醇铵三乙醇铵,以及与之相反的γcmc顺序:乙醇铵二乙醇铵三乙醇铵。粘度大小顺序为:乙醇铵二乙醇铵三乙醇铵,有机反离子的粘度要大于无机反离子。这与分子量、氢键大小的关系是一致的。总体来说发泡能力:乙醇铵二乙醇铵三乙醇铵,这和γcmc的顺序相符。有机反离子的发泡能力要高于无机反离子。另外,对于同种反离子,全氟辛基磺酸盐的胶束化能力、粘度和发泡能力均明显高于全氟辛酸盐,但是全氟辛基磺酸盐的γcmc要略高于全氟辛酸盐。通过量子化学计算表明分子结构中磺酸根头基的负电荷要小于羧酸根,这样表面活性剂全氟辛基磺酸根的头基与反离子的结合能力要弱于全氟辛酸根,从而导致了溶液表面吸附层中全氟辛酸盐在反离子的协同作用下排列更为紧密。

Study on properties of ethanol ammonium salts of perfluorooctanoate and perfluorooctylsulfonate surfactants

The properties of monoethanol ammonium/diethanol ammonium/triethanol ammonium perfluorooctanoate and perfluorooc-tylsulfonate were investigated by measurements of surface tension,foaming and viscosity.Similar effects of counterions were observed both for perfluorooctanoates and perfluorooctylsulfonates.The effect could be ascribed to the terms of hydrophobicity and steric effect of counterions,which respectively resulted in the sequence of cmc(monoethanol ammonium＞diethanol ammonium＞triethanol ammonium) and the reverse sequence of γ_(cmc) (monoethanol ammonium＜diethanol ammonium＜triethanol ammonium).The viscosity increased with molecular weight and the extent of hydrogen bond,which was in the sequence of monoethanol ammonium＜diethanol ammonium＜triethanol ammonium.Organic counterions induced a larger viscosity compared with inorganic counteion.The ability of foaming decreased in the sequence monoethanol ammonium＞diethanol ammonium＞triethanol ammonium,which was consistent with the sequence of γ_(cmc).Organic counterions induced larger foaming ability than inorganic counteion.Meanwhile,for the same counterion,perfluorooctylsulfonates exhibited significantly higher micellization ability,viscosity and foaming ability than those of perfluorooctanoates.however,the γ_(cmc) of perfluorooctylsulfonates were larger than that of perfluorooctanoates.Quantum chemical calculations showed that the negative charge of the sulfonic headgroup was smaller than that of carboxyl headgroup,thus the headgroup of perfluorooctylsulfonate would exhibit smaller binding ability to counterions than the headgroup of perfluorooctanoate,which resulted in a more compact arrangement of perfluorooctanoate with the synergism of counterions in the surface adsorbed layer.