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<p>Clusteroluminescence (CL) refers to the emergent luminescence observed in certain nonconjugated structures, particularly in polymer systems. In most cases, CL exhibits excitation-dependent emission, which is commonly explained by multiple intrachain and interchain through-space conjugation (TSC). However, in some systems, a permanent and excitation-independent emission is observed, which cannot be fully explained by the current TSC mechanism. In this work, through a systematic investigation of polyethylene glycol (PEG) with different molecular weights, we discovered the coexistence of two types of emission in high-molecular-weight PEG: (Type I) a distinct, excitation-independent emission with well-resolved fine structure at 395 nm, and (Type II) a broad, excitation-dependent long-wavelength emission. The Type II emission is generally attributed to through-space <i>n</i>-<i>n</i> conjugation within oxygen clusters. In contrast, combined theoretical and photophysical studies indicate that the origin of Type I emission is negative hyperconjugation between neighboring oxygen atoms and sp<sup>3</sup> carbons. This work not only demonstrates the crucial role of negative hyperconjugation in CL but also clarifies the importance of polymerization in amplifying weak electronic interactions, thereby enabling emergent photophysical properties in polymers.</p>

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Negative hyperconjugation facilitated the intrinsic photoluminescence of polyether

  • 期刊论文

  • 发表日期：

    2025年11月10日

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  • Kailuo Chen,
  • Xiong Liu,
  • Xiang Li,
  • Jianyu Zhang,
  • Jing Zhi Sun,
  • Haoke Zhang,
  • Xing-Hong Zhang,
  • Ben Zhong Tang

摘要

Clusteroluminescence (CL) refers to the emergent luminescence observed in certain nonconjugated structures, particularly in polymer systems. In most cases, CL exhibits excitation-dependent emission, which is commonly explained by multiple intrachain and interchain through-space conjugation (TSC). However, in some systems, a permanent and excitation-independent emission is observed, which cannot be fully explained by the current TSC mechanism. In this work, through a systematic investigation of polyethylene glycol (PEG) with different molecular weights, we discovered the coexistence of two types of emission in high-molecular-weight PEG: (Type I) a distinct, excitation-independent emission with well-resolved fine structure at 395 nm, and (Type II) a broad, excitation-dependent long-wavelength emission. The Type II emission is generally attributed to through-space n-n conjugation within oxygen clusters. In contrast, combined theoretical and photophysical studies indicate that the origin of Type I emission is negative hyperconjugation between neighboring oxygen atoms and sp3 carbons. This work not only demonstrates the crucial role of negative hyperconjugation in CL but also clarifies the importance of polymerization in amplifying weak electronic interactions, thereby enabling emergent photophysical properties in polymers.