关键词: 表面活性剂, 核磁共振谱法, 环糊精, 熵, 离解平衡, 疏水性质, 表面张力, 驱动, 包合物, 糖淀粉

With cyclodextrin (a- and b-CD) and Na carboxymethylamylose (Na-CMA) substrates, and with H(CF2)12CO2K, CH3(CH2)10CO2K, Cl(CF2)8CH2CH2N+Me3I- (I), CH3(CH2)8CH2N+Me3I- (II), Cl(CF2)10CH2CH2N+Me3I- and CH3(CH2)10CH2N+Me3I- (III) as guests, the different behaviors of fluorocarbon and hydrocarbon surfactants were studied by surface tension measurements. Limited cavity size prevents the inclusion of fluorocarbon surfactants by a-CD, but the binding by b-CD is stronger for the fluorocarbon (I) than that for its hydrocarbon analog (II). A comparison of the thermodn. parameters of the b-CD binding process for (I) and (III) reveals that for the former the binding process is driven by entropy or hydrophobic forces, but for the latter the process is enthalpy-favored. Notably, Na-CMA fails to bind the fluorocarbons. A crucial difference between the cyclodextrins and the amylose-type hosts lies in the fact that the former possess pre-organized cavities whereas the latter have to readjust their conformations from loose and extended helices with random coils to interrupted helices during the process of binding. Apparently, this extra energy requirement demands contributions from lipophilic interactions for accomplishment which do not exist between fluorocarbon chains and the hosts. Thus lipophilic forces are significant in hydrophobic-lipophilic interactions.

Key words: SURFACTANTS, NMR SPECTROMETRY, CYCLODEXTRIN, ENTROPY, DISSOCIATION EQUILIBRIUM, HYDROPHOBIC PROPERTIES, SURFACE TENSION, DRIVE, CLATHRATES, AMYLOSE