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中文摘要: 以N,N-二甲基十四胺和1,8-二溴辛烷反应生成了14-8-14型Gemini季铵盐表面活性剂，通过单因素试验优化了反应条件，确定较佳合成条件为：N,N-二甲基胺的用量为5 mmol，N,N-二甲基胺与二溴烷烃的摩尔比为2.2∶1，溶剂乙腈用量为10 mL，反应温度为80 ℃，反应时间为24 h，在此条件下合成了24种m-n-m型Gemini季铵盐表面活性剂，大部分反应的收率大于80%。采用吊环法对产物的表面张力进行了测定，分别研究了疏水烷基链、连接基对Gemini季铵盐表面活性剂表面活性的影响，研究发现，当连接基n相同时，随着疏水烷基链的增长(m>10时)，Gemini季铵盐表面活性剂的表面张力呈现先降低后增加的趋势，14-n-14型Gemini季铵盐表面活性剂呈现出最好的表面活性；当疏水烷基链m=14时，随着连接基n的增大，Gemini季铵盐表面活性剂的表面张力呈现先增大后减小的趋势。
Abstract:A quaternary ammonium Gemini surfactant (14-8-14) was synthesized from N,N-dimethyl tetradecylamine and 1,8-dibromooctane. The optimum reaction condition was obtained by single factor experiment. The optimum synthesis condition was as follows: the dosage of N,N-dimethyl amine was 5 mmol; the molar ratio of n(N,N-dimethyl amine)∶n(dibromoalkane) was 2.2∶1; 10 mL acetonitrile was used as solvent; the reaction temperature was 80 ℃; and the reaction time was 24 h. 24 kinds of quaternary ammonium Gemini surfactants m-n-m were synthesized under this condition, most of which had a yield larger than 80%. The surface tension of the products were determined. The effects of the hydrophobic alkyl chain and the spacer on the surface activity of Gemini surfactants were studied. The results show that, for the same spacer n, the surface tension of Gemini surfactants first decreases and then increases with the increase of hydrophobic alkyl chain length (m>10). 14-n-14 Gemini surfactants exhibit the best surface activity. Moreover, when the hydrophobic alkyl chain m=14, the surface tension of Gemini surfactants first increases and then decreases with the increase of the spacer length n.
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