Self-Assembled Azo-Benzothiazole Mesogens: Align the Structure and Follow the Heat to Uncover Anisotropic Photothermal Pathways.

Abstract

Understanding the relationship between molecular structure and anisotropic photothermal behavior is essential for developing light-responsive materials with directionally controllable behavior. In this study, we report the design of a thiazole-functionalized azobenzene mesogen, PB-ABT, which exhibits efficient photothermal conversion under 405 nm light. The introduction of an electron-rich thiazole moiety induces intramolecular charge transfer (ICT), enhancing π-π stacking and facilitating non-radiative decay pathways essential for thermal energy generation. Comparative studies with a symmetric reference compound (PB-Azo) reveal that PB-ABT exhibits stronger intermolecular interaction, more stable self-assembly, and significantly improved anisotropic photothermal behavior. The identification of a clear correlation between molecular arrangement and directional photothermal dissipation provides answers to the long-standing limitations of isotropic behavior and the unclear mechanisms in organic photothermal systems. These anisotropic photothermal properties originate from two key factors: anisotropic surface morphology and direction-dependent non-radiative dissipation occurring along π-π stacking pathways, demonstrating a direct link between molecular arrangement and macroscopic heat generation. This work provides a molecular-level strategy for constructing 405 nm-responsive organic materials with both optical and thermal anisotropy, offering new insight into the design of aligned photothermal systems for advanced encryptable applications.