Piccinini Esteban, Tuninetti Jimena S, Irigoyen Otamendi Joseba, Moya Sergio E, Ceolín Marcelo, Battaglini Fernando, Azzaroni Omar
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) - Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata - CONICET, Suc. 4, CC 16, La Plata, Argentina.
Soft Matter Nanotechnology Group, CIC BiomaGUNE. Paseo Miramón 182, 20009 San Sebastián, Gipuzkoa, Spain.
Phys Chem Chem Phys. 2018 Apr 4;20(14):9298-9308. doi: 10.1039/C7CP08203G.
Interfacial supramolecular architectures displaying mesoscale organized components are of fundamental importance for developing materials with novel or optimized properties. Nevertheless, engineering the multilayer assembly of different building blocks onto a surface and exerting control over the internal mesostructure of the resulting film is still a challenging task in materials science. In the present work we demonstrate that the integration of surfactants (as mesogenic agents) into layer-by-layer (LbL) assembled polyelectrolyte multilayers offers a straightforward approach to control the internal film organization at the mesoscale level. The mesostructure of films constituted of hexadecyltrimethylammonium bromide, CTAB, and polyacrylic acid, PAA (of different molecular weights), was characterized as a function of the number of assembled layers. Structural characterization of the multilayered films by grazing-incidence small-angle X-ray scattering (GISAXS), showed the formation of mesostructured composite polyelectrolyte assemblies. Interestingly, the (PAA/CTA)n assemblies prepared with low PAA molecular weight presented different mesostructural regimes which were dependent on the number of assembled layers: a lamellar mesophase for the first bilayers, and a hexagonal circular mesophase for n ≥ 7. This interesting observation was explained in terms of the strong interaction between the substrate and the first layers leading to a particular mesophase. As the film increases its thickness, the prevalence of this strong interaction decreases and the supramolecular architecture exhibits a "bulk" mesophase. Finally, we demonstrated that the molecular weight of the polyelectrolyte has a considerable impact on the meso-organization for the (PAA/CTA)n assemblies. We consider that these studies open a path to new rational methodologies to construct "nanoarchitectured" polyelectrolyte multilayers.
展示介观尺度有序组件的界面超分子结构对于开发具有新颖或优化性能的材料至关重要。然而，在材料科学中，将不同结构单元多层组装到表面并控制所得薄膜的内部介观结构仍然是一项具有挑战性的任务。在本工作中，我们证明将表面活性剂（作为介晶剂）整合到逐层（LbL）组装的聚电解质多层膜中，为在介观尺度上控制薄膜的内部结构提供了一种直接的方法。由十六烷基三甲基溴化铵（CTAB）和聚丙烯酸（PAA，不同分子量）构成的薄膜的介观结构，作为组装层数的函数进行了表征。通过掠入射小角X射线散射（GISAXS）对多层膜进行结构表征，表明形成了介观结构的复合聚电解质组装体。有趣的是，用低分子量PAA制备的（PAA/CTA）n组装体呈现出不同的介观结构状态，这取决于组装层数：前几个双层为层状中间相，n≥7时为六方圆形中间相。这一有趣的观察结果是根据底物与第一层之间的强相互作用导致特定中间相来解释的。随着薄膜厚度增加，这种强相互作用的普遍性降低，超分子结构呈现出“本体”中间相。最后，我们证明聚电解质的分子量对（PAA/CTA）n组装体的介观组织有相当大的影响。我们认为这些研究为构建“纳米结构”聚电解质多层膜开辟了新的合理方法途径。
