Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
Nanotechnology Research Centre, National Research Council Canada, 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.
Nanotechnology. 2023 Mar 6;34(20). doi: 10.1088/1361-6528/acbbd1.
Blended films comprising poly(butyl acrylate) (PBA)-grafted cellulose nanocrystals (CNCs) and poly(3-hexylthiophene) (P3HT), exhibited more intense photoluminescence (PL) and longer PL emission lifetimes compared to pristine P3HT films. Optical absorption and photoluminescence spectra indicated reduced torsional disorder i.e. enhanced backbone planarity in the P3HT@CNC blended composites compared to the bare P3HT. Such molecule-level geometrical modification resulted in both smaller interchain and higher intrachain exciton bandwidth in the blended composites compared to the bare P3HT, because of reduced interchain interactions and enhanced intrachain order. These results indicate a potential switch of the aggregation behavior from dominant H-aggregates to J-aggregates, supported by Raman spectroscopy. The reorganization of micromolecular structure and concomitant macroscopic aggregation of the conjugated polymer chains resulted in a longer conjugation length for the P3HT@CNC blended composites compared to the bare P3HT. Additionally, this nanoscale morphological change produced a reduction in the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap of the blends, evidenced from optical absorption spectra. Classical molecular dynamics simulation studies predicted the probability of enhanced planarity in the polymer backbone following interactions with CNC surfaces. Theoretical results from density functional theory calculations corroborate the experimentally observed reduction of optical bandgap in the blends compared to bare P3HT. The blended composite outperformed the bare P3HT in nitro-group PL sensing tests with a pronounced difference in the reaction kinetics. While the PL quenching dynamics for bare P3HT followed Stern-Volmer kinetics, the P3HT@CNC blended composite exhibited a drastic deviation from the same. This work shows the potential of a functionalized rod-like biopolymer in tuning the optoelectronic properties of a technologically important polymeric organic semiconductor through control of the nanoscale morphology.
包含接枝纤维素纳米晶体（CNC）的聚（丙烯酸丁酯）（PBA）和聚（3-己基噻吩）（P3HT）的共混膜与原始 P3HT 薄膜相比，表现出更强的光致发光（PL）和更长的 PL 发射寿命。光学吸收和光致发光光谱表明，与裸 P3HT 相比，在 P3HT@CNC 共混复合材料中，扭转无序即主链平面性增强。这种分子水平的几何修饰导致共混复合材料中的激子带宽在链间和链内都比裸 P3HT 更小，因为链间相互作用减少，链内有序性增强。这些结果表明，由于拉曼光谱的支持，聚集行为可能从主导的 H-聚集态转变为 J-聚集态。由于共轭聚合物链的微观结构重组和随之而来的宏观聚集，与裸 P3HT 相比，P3HT@CNC 共混复合材料的共轭长度更长。此外，这种纳米尺度的形态变化导致共混物的最高占据分子轨道（HOMO）-最低未占据分子轨道（LUMO）能隙减小，这可以从光学吸收光谱中得到证明。经典分子动力学模拟研究预测，聚合物主链与 CNC 表面相互作用后，其平面化的概率会增加。密度泛函理论计算的理论结果证实了与裸 P3HT 相比，共混物的光学带隙减小。与裸 P3HT 相比，共混复合材料在硝基基团 PL 传感测试中表现更好，其反应动力学有明显差异。虽然裸 P3HT 的 PL 猝灭动力学遵循 Stern-Volmer 动力学，但 P3HT@CNC 共混复合材料则明显偏离了这一规律。这项工作展示了功能化棒状生物聚合物通过控制纳米形貌来调节技术上重要的聚合物有机半导体的光电性能的潜力。
