三种不同分子结构阴离子表面活性剂胶束微结构的NMR研究

用核磁共振测定自旋-晶格、自旋-自旋弛豫时间(t₁,t₂)、自扩散系数(D),用2DNOESY技术对正十四烷基硫酸钠、β-戊基壬烷基硫酸钠和β-戊基壬烷基聚氧乙烯醚(4)硫酸钠三类阴离子表面活性剂水溶液进行了观测,烷烃链各基团的t₂/t₁值给出了这三类分子形成各自胶束的水合层位点信息以及烷烃链在胶束内核中堆积程度的比较,自扩散系数结果表明,β-戊基壬烷基硫酸钠比正十四烷基硫酸钠形成的胶束的水合动力学半径小,但β-戊基壬烷基聚氧乙烯醚(4)硫酸钠形成的胶束水合动力学半径明显大于其它两类表面活性剂胶束,2DNOESY谱图提供了β-戊基壬烷基聚氧乙烯醚(4)硫酸钠分子中聚氧乙烯基键在胶束外层卷曲排列的信息.

NMR Study on the Micellar Microstructures of Three Anionic Surfactants with Different Molecular Structures in Aqueous Solution

The comparison of the micellar microstructures among three pure surfactant aqueous solutions with different molecular structures such as sodium alkylsulfates with normal, branched alkyl chains and with the polyethylene oxide chain inserted between the alkyl chain and the sulfatc polar head has been performed by using nuclear magnetic resonance spin-lattice relaxation time(t1) , spin-spin relaxation time(t2) self-diffusion coefficient and two dimensional nuclear Overhause enhanced spectroscopy techniques. According to the ratios of t2 to t1, the hydration layers of the micelles were deduced. The t2/t1 values show that the hydrocarbon chains of surfactant I arc more compact in the micelles than that of surfactant I . NMR self-diffusion coefficients show that the micelles formed from surfactant I are larger than those from surfactant n . At last, the 2D NOESY technique was applied to confirm the arrangement of the polyethylene oxide chains outside the hydrophobic micelles.