N-(3-二甲氨基)丙基全氟烷基磺酰胺盐酸盐的表面活性

Surface activities of N-(3-dimethyl amino) propyl perfluoroalkylsulfonamide hydrochloride

全氟烷基磺酰氟与3-二甲氨基丙胺的缩合产物用盐酸酸化制备了具有不同长度全氟烷基的阳离子氟表面活性剂（CnF2n＋1SO2NH（CH2）3NH（CH3）2^＋Cl^-,n=4,6,8,简称PFB-MC,PFH-MC和PFO-MC）。用滴体积法测定了pH=2.6-2.7时该类表面活性剂单体系及加盐（0.1 mol·L^-1NaCl）后的表面张力。随着氟碳链长增加,临界胶束浓度（cmc）减小,但表面饱和吸附量降低（单分子极限吸附面积增大）;单体系最低表面张力（γcmc）PFH-MC最小（15.02 mN·m^-1）,明显低于PFB-MC,而PFO-MC与PFH-MC的γcmc相比反略有上升。外加盐能降低体系的cmc,但由于过量盐酸的存在对γcmc无明显影响。研究了表面活性剂在cmc前后的表面张力随pH的变化,发现酸度增强到一定值后表面张力急剧下降。结果表明该系列表面活性剂适用于强酸性环境、抗盐且具有极高的表面活性。

A series of cationic fluorinated surfactant with different perfluoro alkyl carbon chain length[CnF2n＋1SO2NH（CH2）3NH（CH3）2^＋Cl^-,n=4,6,8,abbreviated as PFB-MC,PFH-MC and PFO-MC,respectively] were prepared by acidification of the condensation product of corresponding perfluoroalkylsulfonyl fluoride and 3-dimethyl aminopropyl amine with hydrochloric acid.The surface tension of the sheer solution of these surfactants and the surfactant solutions with the presence of salt（0.1 mol·L^-1 NaCl） were measured with drop volume method at pH=2.6～2.7.As the perfluoroalkyl carbon chain length increases,the corresponding critical micelle concentration（cmc） decreases and the saturated surface adsorption decreases（limit adsorptive surface area per molecule increases）.PFH-MC shows the lowest minimum surface tension（γcmc） 15.02 mN·m^-1 among the sheer solutions of these surfactants,which is significantly lower than that of PFB-MC,while the γcmc of PFO-MC is slightly higher than that of PFH-MC.The addition of salt could reduce the cmc of these surfactant systems but no significant influence on γcmc was observed due to the existence of excess hydrochloric acid.The influence of pH on the surface tension of surfactants at concentrations above and below their cmc value respectively,was further studied.Results showed that when the acidity increased to a certain extent the surface tension decreases abruptly.Obviously,this kind of surfactant has very high surface activity under strong acidic condition and has good resistance against salt content.