Document Type
Article
Publication Date
11-1-2025
Abstract
Establishing direct correlations between molecular motion, crystal structure, and macroscopic properties is essential for designing responsive functional materials. Herein, we report a malononitrile-based aggregation-induced emission luminogen (AIEgen), TPA-CN, that crystallizes into multiple polymorphs exhibiting distinct optoelectronic behaviors. In dilute solution, TPA-CN exhibits excitation-dependent emission spanning from sky blue to red under irradiation from 375 to 425 nm, arising from conformational flexibility and multiple excited-state transitions. In the solid state, subtle differences in crystal packing—governed by torsional angles and intermolecular interactions that modulate dipole moments—lead to pronounced variations in luminescence color and piezoelectric response. Mechanical grinding induces mechanochromic emission shifts without phase transitions, as confirmed by powder X-ray diffraction (PXRD). Comparative analysis of crystallographic data, Hirshfeld surface mapping, and non-covalent interaction (NCI) calculations reveals that weak intermolecular interactions critically regulate crystal packing, ultimately producing distinct emission colors and behaviors. Notably, the non-centrosymmetric polymorph (Pca2₁) exhibits strain-sensitive piezoelectric currents up to 562 pA under 0.51 % strain, with a piezoelectric coefficient (d₃₃) of 1.77 pm·V¹ and a low Young's modulus of 6.75 GPa. Parallel device configurations further enhance mechanical sensitivity, enabling detection of microvibrations. This study reveals how minor conformational changes, and polymorphic packing can orchestrate dual photonic and piezoelectric functions, establishing a unified motion–structure–property paradigm. These insights advance the rational design of multifunctional organic materials for flexible sensing, soft electronics, and energy-harvesting applications.
Keywords
aggregation-induced emission (AIE), excitation-dependent emission, mechanofluorochromism, motion–structure–property relationship, piezoelectric properties
Language
English
Publication Title
Chemical Engineering Journal
Grant
21975054
Rights
© 2025 The Authors. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/), which permits non-commercial copying and redistribution of the material in any medium or format, provided the original work is not changed in any way and is properly cited.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Huang, K., Jiang, T., Liang, J., Chen, X., Liu, W., Cai, W., ... & Feng, X. (2025). Molecular motion–structure–property correlation in a polymorphic AIEgen with mechanochromic and piezoelectric functions. Chemical Engineering Journal, 168741. https://doi.org/10.1016/j.cej.2025.168741
Manuscript Version
Final Publisher Version