Kikuchi Mao, Hamaguchi Hiroto, Yamamoto Katsuhiro, Nishitsuji Shotaro, Nagano Shusaku, Ebe Hinako, Matsui Jun
Graduate School of Science and Engineering, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan.
Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
Soft Matter. 2025 Jul 30. doi: 10.1039/d5sm00313j.
The fabrication of polymer lamellar films with sub-10 nm periodicity and perpendicularly aligned structures is essential for applications in lithography and separation membranes. In this study, annealing an amphiphilic statistical copolymer, poly(-octadecyl acrylamide--(2-hydroxyethyl acrylamide)), in water induces the formation of perpendicularly oriented lamellae, where the lamellar planes align perpendicular to the substrate. The statistical copolymer with a 1 : 1 comonomer composition is synthesized free-radical polymerization, and thin films are prepared by spin coating. The nanoscale phase-separated structures formed by annealing in water are analyzed. Structural analysis using two-dimensional grazing-incidence small-angle X-ray scattering reveals that the annealed films exhibit both parallel and perpendicular lamellae with the periodicity of 4.2-5.7 nm, and the formation of perpendicular lamellae was strongly influenced by direct contact with water. Furthermore, depth-dependent XRD studies using low-energy grazing-incidence small-angle X-ray scattering show that parallel lamellae form at the topmost film surface, while perpendicular lamellae develop in the interior. Water contact angle and Fourier-transform infrared spectra measurements further confirm this structure. Exposure to water induces alignment of the hydrophobic octadecyl side chains parallel to the substrate, promoting the formation of perpendicular lamellae in the film interior. In addition, experiments with thin films sandwiched between hydrophilic or hydrophobic glass substrates demonstrate that the nature of the interface plays a crucial role in determining the lamellar alignment. These findings emphasize the importance of interface modification in controlling thin-film structures and provide insights for designing functional materials with tailored properties.
制备具有低于10纳米周期性和垂直排列结构的聚合物层状薄膜对于光刻和分离膜应用至关重要。在本研究中，在水中对两亲性统计共聚物聚（-十八烷基丙烯酰胺- -（2-羟乙基丙烯酰胺））进行退火处理会诱导形成垂直取向的片层，其中片层平面与基底垂直对齐。通过自由基聚合合成具有1:1共聚单体组成的统计共聚物，并通过旋涂制备薄膜。分析了在水中退火形成的纳米级相分离结构。使用二维掠入射小角X射线散射进行的结构分析表明，退火后的薄膜呈现出周期性为4.2 - 5.7纳米的平行和垂直片层，并且垂直片层的形成受到与水直接接触的强烈影响。此外，使用低能掠入射小角X射线散射进行的深度相关XRD研究表明，平行片层在薄膜最顶层表面形成，而垂直片层在内部发展。水接触角和傅里叶变换红外光谱测量进一步证实了这种结构。与水接触会诱导疏水的十八烷基侧链平行于基底排列，促进薄膜内部垂直片层的形成。此外，用夹在亲水或疏水玻璃基底之间的薄膜进行的实验表明，界面的性质在决定片层排列方面起着关键作用。这些发现强调了界面改性在控制薄膜结构中的重要性，并为设计具有定制性能的功能材料提供了见解。
