INQUIMAE-CONICET and DQIAQF, University of Buenos Aires, School of Sciences, Ciudad Universitaria, Pabellón 2, Ciudad Autónoma de Buenos Aires C1428EHA, Argentina.
Soft Matter. 2018 Apr 25;14(16):3171-3181. doi: 10.1039/c8sm00096d.
In this work, a molecular theory is used to study the self-assembly of short diblock and triblock amphiphiles, with head-tail and head-linker-tail structures, respectively. The theory was used to systematically explore the effects of the molecular architecture and the affinity of the solvent for the linker and tail blocks on the relative stability of the different nanostructures formed by the amphiphiles in dilute solution, which include spherical micelles, cylindrical fibers and planar lamellas. Moreover, the theory predicts that each of these nanostructures can adopt two different types of internal organization: (i) normal nanostructures with a core composed of tail segments and a corona composed of head segments, and (ii) nanostructures with a core formed by linker segments and a corona formed by tail and head segments. The theory predicts the occurrence of a transition from micelle to fiber to lamella when increasing the length of the tail or the linker blocks, which is in qualitative agreement with the geometric packing theory and with experiments in the literature. The theory also predicts a transition from micelle to fiber to lamella as the affinity of the solvent for the tail or linker block is decreased. This result is also in qualitative agreement with experiments in the literature but cannot be explained in terms of the geometric packing theory. The molecular theory provides an explanation for this result in terms of the competition between solvophobic attractions among segments in the core and steric repulsions between segments in the corona for the different types of self-assembled nanostructures.
在这项工作中，使用分子理论研究了短二嵌段和三嵌段两亲物的自组装，分别具有头-尾和头-接头-尾结构。该理论被用于系统地探索分子结构和溶剂对接头和尾块的亲和力对在稀溶液中形成的不同纳米结构的相对稳定性的影响，这些纳米结构包括球形胶束、圆柱形纤维和平面薄片。此外，该理论预测这些纳米结构中的每一种都可以采用两种不同类型的内部组织：(i) 由尾部片段组成核心和由头部片段组成冠的正常纳米结构，和 (ii) 由接头片段组成核心和由尾部和头部片段组成冠的纳米结构。该理论预测，当增加尾部或接头块的长度时，从胶束到纤维到层状的转变会发生，这与几何堆积理论和文献中的实验定性一致。该理论还预测了随着溶剂对尾部或接头块的亲和力的降低，从胶束到纤维到层状的转变。这一结果也与文献中的实验定性一致，但不能用几何堆积理论来解释。分子理论根据核心中各段之间的疏水性吸引力与冠中各段之间的空间排斥作用之间的竞争，为不同类型的自组装纳米结构提供了一个解释。
