Gao Meihua, Du Na, Yao Zhiyin, Li Ying, Chen Nan, Hou Wanguo
Key Laboratory of Colloid & Interface Chemistry (Ministry of Education), Shandong University, Jinan 250100, China.
Soft Matter. 2021 Mar 11;17(9):2490-2499. doi: 10.1039/d0sm02229b.
Simple single-chain amphiphiles (SCAs) can form vesicular structures in their single-component aqueous solutions, which has attracted great attention, but the understanding of their aggregation behavior is still limited. In this work, the aggregation behavior of 4-dodecylbenzene sulfonic acid (DBSA), a typical simple SCA, in water was investigated. The structure and properties of the aggregates formed were determined. In particular, the effect of wet-dry cycles on the structures of aggregates was examined. The mechanisms of aggregate formation and structural transition were discussed. It was found that the increase of DBSA concentration can drive the occurrence of a micelle-to-vesicle transition, showing a critical micelle concentration and critical vesicle concentration of ∼0.53 and 2.14 mM, respectively. The vesicles formed coexist with micelles in solution, with a unilamellar structure and ∼80 nm size, and exhibit size-selective permeability. In addition, the vesicles show remarkable stability upon long-term storage, exposure to high temperature, and freeze-thaw cycles. The H-bonding interaction between DBSA species and the interdigitated structure of alkyl chains in bilayers play a key role in the formation and stability of DBSA vesicles. Interestingly, it was found that the wet-dry cycle can induce a micelle-to-vesicle transition and an obvious increase in the size of the original vesicles, accompanied by the formation of some multilamellar vesicles. This work provides a better understanding of the aggregation behavior of simple SCAs in their single-component aqueous solutions.
简单的单链两亲分子（SCAs）在其单组分水溶液中能够形成囊泡结构，这引起了极大关注，但对其聚集行为的理解仍然有限。在这项工作中，研究了典型的简单SCA——4-十二烷基苯磺酸（DBSA）在水中的聚集行为。确定了所形成聚集体的结构和性质。特别地，研究了干湿循环对聚集体结构的影响。讨论了聚集体形成和结构转变的机制。结果发现，DBSA浓度的增加可促使胶束向囊泡转变，临界胶束浓度和临界囊泡浓度分别约为0.53和2.14 mM。形成的囊泡与溶液中的胶束共存，具有单层结构，尺寸约为80 nm，并表现出尺寸选择性渗透性。此外，囊泡在长期储存、高温暴露和冻融循环下表现出显著的稳定性。DBSA分子间的氢键相互作用以及双层中烷基链的叉指结构在DBSA囊泡的形成和稳定性中起关键作用。有趣的是，发现干湿循环可诱导胶束向囊泡转变，并使原始囊泡尺寸明显增大，同时伴有一些多层囊泡的形成。这项工作有助于更好地理解简单SCA在其单组分水溶液中的聚集行为。
