NMR研究溶液中正十四烷基硫酸钠/正十四烷基聚氧乙烯醚(3)表面活性剂之间的相互作用

采用¹HNMR弛豫、自扩散系数和二维相敏(2DNOESY)实验研究了正十四烷基硫酸钠n-CH₃(CH₂)₁₃OSO₃Na(STS)]和正十四烷基聚氧乙烯醚(3)n-CH₃(CH₂)₁₃O(C₂H₄O)₃H(C₁₄E₃)]在溶液中的自聚集以及二者混合后的相互作用.结果表明,STS与C₁₄E₃混合后存在相互作用,并形成混合胶束;弛豫实验表明,混合胶束中STS疏水链质子运动更加受阻,C₁₄E₃的α-(4″)和β-CH₂(3″)处链堆积紧密.C₁₄E₃的亲水端(CH₂CH₂0)₃链卷曲紧贴在疏水壳表面外链堆积较紧密处.自扩散系数测量表明,混合胶束比单一阴离子表面活性剂形成的胶束大.单一非离子型胶束和混合胶束的亲水端(CH₂CH₂0)₃(5″)链构成相应较软和松散的外壳.单一C₁₄E₃在极性溶剂氯仿溶液中,质子运动比在水中自由度大,但2DNOESY谱中出现了少量分子间的交叉峰,也可能形成了一些小的聚集体.

Interaction Between Sodium Tetradecyl Sulfate-Tetradecyl Triethoxylated Ether Surfactants in Aqueous Solution by 1H NMR

The self-aggregation of sodium tetradecyl sulfaten-CH3(CH2)13OSO3Na(STS)] and tetradecyl triethoxylated ethern-CH3(CH2)13O(C2H4O)3H(C14E3)] in aqueous solution and the interaction between them were studied by 1H self-diffusion coefficient, relaxation measurements and two-dimensional nuclear overhauser enhancement spectroscopy(2D NOESY). When pure anionic surfactant(STS) formed micelles, the α-CH2 groups were located on the surface layer of the hydrophobic micellar cores. The hydrophobic chains of STS are packed in the interior of the micellar cores. Pure nonionic surfactant(C14E3) formed large micelles in aqueous solution which is evidenced by the appearance of the small broad peaks of the protons on the hydrophobic chain of C 14E 3. 2D NOESY experiments give the evidence that mixed micelles are formed when STS and C14E3were mixed in aqueous solution. The relaxation measurement shows that α-CH2 and β-CH2 of STS and the α-CH2 and β-CH2 of C14E3locate on the surface layers of the mixed micellar cores. The hydrophilic moieties(CH2CH20)3 of the nonionic surfactant crimpe around the hydrophobic micellar cores. The self-diffusion coefficient measurement shows that the mixed micelles are larger than the pure micelles of STS. Softer and more incompact shells surrounding the micellar cores are created by the hydrophilic chains in C14E3micelles and STS/C14E3mixed micelles. The motion of the C14E3protons are more free in chloroform medium, but the appearance of weak cross peaks shown in the 2D NOESY map of this solution suggests that small self-aggregates may be formed.