Li Yuang, Zhu Yingli, Li Xiangcheng, Chen Pingan
The State Key Laboratory of Refractories and Metallurgy, Key Laboratory of High Temperature Electromagnetic Materials and Structure of MOE, Wuhan University of Science and Technology Wuhan 430081 PR China
Chem Sci. 2024 Oct 5;15(43):17988-99. doi: 10.1039/d4sc04320k.
Non-conjugated fluorescent polymers (NCPLs) are of interest due to their remarkable biocompatibility, processability and biodegradability. However, the realization of multicolor emitting NCPLs through structure modulation remains a great challenge. In this work, a series of novel yttrium-branched polyborosilazane (PBSZ) structures (PY1-PY3) were prepared. PBSZ exhibits a blue emission peaked at 450 nm, and the introduction of an yttrium-branched-chain generates a new long-wavelength emission center. As the degree of yttrium branching increases, the emerged emission peak shifts from 532 to 646 nm, and its intensity gradually increases to 1.4 times that of the blue emission. CIE chromaticity coordinates indicate that yttrium-branching modulates the emission color from blue (0.19, 0.21) to near white (0.34, 0.40) and red (0.43, 0.36). Particularly, the PY3 sample exhibits an ultra-broad emission spectrum; covering the range of 400-750 nm. Theoretical calculation indicates that the yttrium-branched-chains promote heteroatom delocalization to form "cluster chromophores", generating new orbitals with lower gaps. In addition, experimental results prove that the yttrium-branched-chains balance the flexibility of the molecular backbone and generate stable fluorescent clusters, which intensifies the non-conjugated linking and through-space-conjugation (TSC) effects, thus generating long-wavelength emission. This work proves that yttrium "end-grafting" is a feasible strategy for equilibrium flexibility and to realize full-color emission in non-conjugated polymers.
非共轭荧光聚合物（NCPLs）因其卓越的生物相容性、可加工性和生物降解性而备受关注。然而，通过结构调制实现多色发射的NCPLs仍然是一个巨大的挑战。在这项工作中，制备了一系列新型的钇支化聚硼硅氮烷（PBSZ）结构（PY1 - PY3）。PBSZ在450 nm处呈现出蓝色发射峰，钇支链的引入产生了一个新的长波长发射中心。随着钇支化程度的增加，出现的发射峰从532 nm移至646 nm，其强度逐渐增加至蓝色发射强度的1.4倍。CIE色度坐标表明，钇支化将发射颜色从蓝色（0.19, 0.21）调制为近白色（0.34, 0.40）和红色（0.43, 0.36）。特别地，PY3样品表现出超宽发射光谱，覆盖400 - 750 nm范围。理论计算表明，钇支链促进杂原子离域以形成“簇生发色团”，产生具有更低能隙的新轨道。此外，实验结果证明，钇支链平衡了分子主链的柔韧性并产生稳定的荧光簇，这增强了非共轭连接和空间共轭（TSC）效应，从而产生长波长发射。这项工作证明钇“端接枝”是平衡柔韧性并在非共轭聚合物中实现全色发射的可行策略。
