动态亚胺型pH开关表面活性剂的合成及性能研究

Synthesis and properties of pH-switchable surfactants based on dynamic imine bond

基于动态亚胺键特殊的pH响应特性,构筑具有pH可逆响应的表面活性剂及其自组装体系是近年来表面活性剂物理化学领域的热点之一,但是两性离子型的动态亚胺键表面活性剂尚未见报导。为此,设计并合成一种带有磺基甜菜碱亲水基的芳香醛(FPSA,(CHO)C_(6)H_(4)OCH_(2)CH_(2)N^(+)(CH_3)_(2)CH_(2)CH_(2)CH_(2)SO_(3)^(-))的前驱体,并与脂肪辛基伯胺(OA)在水溶液中原位形成动态亚胺键型表面活性剂FPSA-OA(C_(8)H_(17)N=CH-C_(6)H_(4)OCH_(2)CH_(2)N^(+)(CH_3)_2CH_(2)CH_(2)CH_(2)SO_(3)^(–))。通过表面张力(γ)曲线得到25℃时FPSA-OA的临界胶束浓度(cmc)为3.43×10^(-3)mol/L,γcmc为30.89 m N/m;此外,FPSAOA可以将石油醚-水的界面张力降低至4.87 m N/m,表现出良好的表(界)面活性。结果表明,FPSA-OA具有pH响应性,其p H开关窗口为8~12;对于2×10^(-3)mol/L FPSA-OA溶液而言,当pH分别在8和12可逆变化时,其γ在70和37 m N/m之间相应可逆改变;如此循环5次,FPSA-OA水溶液的表面张力均表现出良好的响应可逆性。

Based on the particular pH-response of dynamic imine bonds,constructing p H-responsive surfactants and the self-assemblies thereof has been one of the hotspots recently in the field of physical chemistry of surfactants.However,the reports on amphoteric surfactants containing dynamic imine bonds with simple structure have been rarely seen.Herein,an aromatic aldehyde containing sulfobetaine group(FPSA,(CHO)C_(6)H_(4)OCH_(2)CH_(2)N^(+)(CH_(3))_(2)CH_(2)CH_(2)CH_(2)SO_(3)^(-))was designed and synthesized.FPSA and octylamine(OA)were used as the precursors to form an amphoteric dynamic imine surfactant(FPSA-OA,C_(8)H_(17)N=CH-C_(6)H_(4)OCH_(2)CH_(2)N^(+)(CH_(3))_(2)CH_(2)CH_(2)CH_(2)SO_(3)^(–))in situ in the aqueous solution.The critical micelle concentration(cmc)and the surface tension(γ)at cmc were 3.43×10^(-3)mol/L and 30.89 m N/m at 25℃,respectively.In addition,the interfacial tension at the interface of petroleum ether-water was reduced to 4.87 m N/m.All of these results indicate that the interfacial activities of FPSA-OA are quite well.The p H-response of FPSA-OA was observed,and the p H-responsive window was in the range of 8 to 12.For a sample solution of FPSA-OA(2×10^(-3)mol/L),the value ofγwas reduced from approximately 70 m N/m to 37 m N/m when the p H was changed from 8 to 12,and then restored to approximately 70 m N/m if the p H was changed back to 8.This transition could be steadily and reversibly carried out over 5 cycles without any remarkable variation,which implies that FPSA-OA has an excellent p H-reversibility.