手性赖氨酸基Gemini表面活性剂的表面性能

用表面张力法、电导法和稳态荧光法研究了手性Gemini表面活性剂C₁₂-m-C₁₂] Na₂（m=2，4，6）和C₁₂-T-C₁₂] Na₂的表面性能及临界胶束聚集数，并计算胶束形成的热力学参数，用圆二色谱法考察了C₁₂-2-C₁₂] Na₂在不同浓度下的立体构型. 结果表明，手性Gemini表面活性剂的临界胶束浓度（cmc）和临界表面张力γ_cmc随着连接基链长增加或刚性增强而增大；ΔG_m⁰和ΔH_m⁰为负值，|ΔH_m⁰|比|-TΔS_m⁰|小很多，说明胶束化过程为熵驱动的自发放热过程；随着连接基链长增加或刚性增强，ΔG_m⁰和ΔH_m⁰逐渐增大，ΔS_m⁰和临界胶束聚集数逐渐减小，表明其胶束化能力随之降低；当浓度大于cmc时，手性Gemini表面活性剂可形成手性超分子聚集体.

Surface Activity Properties of Chiral L-Lysine Based Gemini Surfactants

Surface activity properties and critical micelle aggregation numbers of C₁₂-m-C₁₂] Na₂(m=2,4,6) and C₁₂-T-C₁₂] Na₂ were determined by surface tension, electrical conductivity and steady fluorescene probe methods. The values of critical micelle concentration(cmc), γ_cmc and per surfactant molecule(A_min) derived from surface tension measurement were found to be in the order of C₁₂-2-C₁₂] Na₂< C₁₂-4-C₁₂] Na₂< C₁₂-6-C₁₂] Na₂< C₁₂-T-C₁₂] Na₂, which were in aggreement with the sequence of Γ_max. The results show that the surface activites of C₁₂-m-C₁₂] Na₂ and C₁₂-T-C₁₂] Na₂ are high. ΔG_m⁰ and ΔH_m⁰ are negative, the absolute value of ΔH_m⁰ is much smaller than the product of ΔS_m⁰ and temperature in the aqueous solution. The thermodynamic parameters of micellization of the four Gemini surfactants indicate that the micellization process is an enthopy-driven, exothermic and spontaneous process. As the spacer lengthens from 2 to 6 or the rigidity of the spacer strengthens, which results in a decrease in the ability of micelles to form, ΔG_m⁰ and ΔH_m⁰ of the surfactants increase, ΔS_m⁰ and critical micelle aggregation numbers of the surfactants decrease. The circular dichroism indicated the formation of chiral helical aggregates above the cmc.