Nanostructured Molecular Packing of Polymer Films Formed on Water Surfaces.

Sung, Yoori; Lee, Wonseok; Lee, Haechang; Lee, Jin-Woo; Kim, Bumjoon J; Yoo, Seunghyup; Jeong, Seonju; Kim, Jihan et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

In this study, we examined the nanostructured molecular packing and orientations of poly[[<i>N</i>,<i>N</i>'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-<i>alt</i>-5,5'-(2,2'-bithiophene)] (P(NDI2OD-T2)) films formed on water for the application of nanotechnology-based organic electronic devices. First, the nanoscale molecule-substrate interaction between the polymer and water was modulated by controlling the alkyl side chain length in NDI-based copolymers. Increasing alkyl side chain lengths induced a nanomorphological transition from face-on to edge-on orientation, confirmed by molecular dynamics simulations revealing nanostructural behavior. Second, the nanoscale intermolecular interactions of P(NDI2OD-T2) were controlled by varying the volume ratio of the high-boiling-point additive solvent in the binary solvent blends. As the additive solvent ratio increased, the nanostructured molecular orientation of the P(NDI2OD-T2) films on water changed remarkably from edge-on to bimodal with more face-on crystallites, thereby affecting charge transport. Our finding provides essential insights for precise nanoscale morphological control on water substrates, enabling the formation of high-performance polymer films for organic electronic devices.