Coldren Bret A, Warriner Heidi, van Zanten Ryan, Zasadzinski Joseph A, Sirota Eric B
Department of Chemical Engineering, University of California, Santa Barbara, CA 93106-5080, USA.
Proc Natl Acad Sci U S A. 2006 Feb 21;103(8):2524-9. doi: 10.1073/pnas.0507024103. Epub 2006 Feb 8.
Mixtures of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzene sulfonate (SDBS) in water form a fluid lamellar phase at < or = 40 wt % water but surprisingly turn into viscous gels at higher water fractions. The gels are characterized by spherulite and other bilayer defects consistent with a low bending elasticity, kappa approximately k(B)T, and a nonzero spontaneous curvature. Caillé analysis of the small-angle x-ray line shape confirms that for 7:3 wt:wt CTAT:SDBS bilayers at 50% water, kappa = 0.62 +/- 0.09 k(B)T and kappa = -0.9 +/- 0.2 k(B)T. For 13:7 wt:wt CTAT:SDBS bilayers, the measured bending elasticity decreases with increasing water dilution in good agreement with predictions based on renormalization theory, giving kappa(o) = 0.28 k(B)T. These results show that surfactant mixing is sufficient to make kappa approximately k(B)T, which promotes strong, Helfrich-type repulsion between bilayers that can dominate the van der Waals attraction. These are necessary conditions for spontaneous vesicles formed at even higher water fractions to be equilibrium structures.
在水中，对甲苯磺酸十六烷基三甲基铵（CTAT）和十二烷基苯磺酸钠（SDBS）的混合物在水含量≤40 wt%时形成流体层状相，但令人惊讶的是，在较高水含量时会转变为粘性凝胶。这些凝胶的特征是球晶和其他双层缺陷，这与低弯曲弹性（κ≈kBT）和非零自发曲率一致。对小角X射线线形的凯耶分析证实，对于水含量为50%的7:3 wt:wt CTAT:SDBS双层，κ = 0.62±0.09 kBT，κ = -0.9±0.2 kBT。对于13:7 wt:wt CTAT:SDBS双层，测量到的弯曲弹性随着水稀释度的增加而降低，这与基于重整化理论的预测非常吻合，得到κo = 0.28 kBT。这些结果表明，表面活性剂混合足以使κ≈kBT，这促进了双层之间强烈的、类似赫尔弗里希型的排斥力，该排斥力可主导范德华吸引力。这些是在更高水含量下形成的自发囊泡成为平衡结构的必要条件。
