QSPR模型对AE_3SO_3表面活性剂的cmc计算及其分子中EO基团对胶束化的作用

QSPR cmc Calculations for AE_3SO_3 and the Contribution of EO in Micellization

合成并纯化了三种阴离子表面活性剂脂肪醇聚氧乙烯 (3 )醚磺酸钠AE3 SO3 [CnH2n+ 1(OE) 3 SO3 Na (n =12 ,14 ,16) ] .用我们建立的定量结构 -性质相关 (QSPR)模型预测它们的cmc值 ,其结果与表面张力测定的实验值相吻合 ;并用QSPR计算分子中嵌入 0～ 5个EO基团的C12 ESO3 的cmc值 ,表明EO具有疏水性 .从Klevens经验公式和有机概念图均得出 ,EO链对AE3 SO3 疏水性的贡献随烷基链长增加 (n =12～ 16)而逐渐减弱 ,3个EO基团分别相当于 2 .4,2 .3 ,2 .2个CH2 的疏水作用 .热力学计算表明 ,在C12 SO3 中引入第 1个EO后 ,胶束形成的ΔG°mic下降约 3kJ/mol,相当于 1个CH2 的疏水作用 ,而第 2和第 3个EO的引入使ΔG°mic下降约 2kJ/mol,即每个EO基团相当于 1/3个CH2 的疏水作用 ;说明随着分子中EO数增加 ,每个EO基团的疏水性减弱 ,亲水性的作用越来越明显 .长期被认作是亲水基团的EO也具有一定的疏水性 .

Three homologous anionic AE(3)SO(3)[CnH2n + 1(OE)(3)SO3Na (n = 12, 14, 16)]surfactants were synthesized and purified. Firstly, their critical micelle concentration (cmc) predictions were done on an optimum Quantitative Structure-Property Relationship (QSPR) model created previously, and the cmc values were experimentally measured by use of surface tension method. It can be concluded that the QSPR model is valid due to the good agreement between the calculated results and the experimental data. Secondly, it should be emphasized that the EO segment within AESO(3) moiety possesses both hydrophilicity and hydrophobicity. On one hand, from QSPR calculation, Klevens equation and organic concept diagram, the EO segment in AESO(3) moiety exhibits hydrophobicity in micellization. Moreover, with increase in alkyl chain length from 12 to 16 for AE(3)SO(3), the hydrophobicity of EO chain is on a par with that of 2.4, 2.3 and 2.2 CH2 groups respectively. On the other hand, the calculation of the thermodynamic parameters shows that the introduction of the first EO into the dodecyl sulfonate decreases DeltaGdegrees(mic) by about 3 kJ/mol, the same as one CH2 group does. The introduction of the second and the third EO, however, decreases DeltaGdegrees(mic) by about 1 kJ/mol respectively, which reflects that with increase in EO chain the hydrophilicity of the EO unit gets increased.