LSmn系列表面化学性质与胶束化作用

通过表面张力的测定, 研究了十二烷基聚氧乙烯聚氧丙烯醚(LSmn)系列表面活性剂LS36、LS45、LS54在溶液表面吸附和形成胶束的热力学函数随温度的变化. 给出了它们在水溶液中的二组分相图.结果表明, LS36、LS45、LS54的表面活性都较高. 在25～50 ℃范围内, 临界胶束浓度(cmc)和平衡表面张力分别在4.44×10－6～17.3×10－6 mol?L－1和30.1～33.5 mN?m－1之间, 表面吸附和形成胶束的自由能分别在－40.0～－49.5 kJ?mol－1和－27.2～－33.1 kJ?mol－1之间.不论是在溶液表面吸附还是形成胶束均为熵驱动过程.其中LS36由于含具有亲水能力较强的聚氧乙烯基团(EO)成分较低, 因此不论其浊点还是其表面吸附和形成胶束的热力学函数均与LS45、LS54具有较大差异.

Surface Activity and Micellization of LSmn in Aqueous Solution

In order to investigate the surfactivity of the linear dodecyl polyoxyethylene polyoxypropylene ether series (LSmn), the surface tensions of LS36, LS45 and LS54 have been respectively measured at 298, 303, 313 and 323 K in aqueous solution. Their phase diagrams in water have also been separately made. The critical micelle concentration(cmc) and the corresponding surface tension at such concentration (γcmc) are determined from their γ－lgc curves, which is in the ranges 4.44×10－6～17.3×10－6 mol?L－1 and 30.1～33.5 mN?m－1, respectively. The thermodynamic functions on surface adsorption at cmc and on micellization have also been calculated, in which the adsorption and the micellization free energies (ΔGadΘ and ΔGmΘ) respectively are in the ranges －40.0～－49.5 kJ?mol－1 and －27.2～－33.1 kJ?mol－1 in the studied temperature range. The thermodynamic data show that both the adsorption and the micelliration processes for the studied surfactants are driven by entropy and that LS36 is much different from LS45 and LS54 in many aspects, due to its less component of polyoxyethylene group which has strong hydrophilic capacity in its hydrophilic segment.