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<p>Hyperbranched polysiloxanes (HBPSi) are novel non-conjugated polymers with aggregation-induced emission (AIE) and modifiable terminals, and have attracted attention due to their unique topology and functional potential. In this study, two AIE-active HBPSi derivatives (OA-HBPSi and IBO-HBPSi, where OA stands for oleic acid and IBO stands for isobutyric acid) containing C=C and acyloxy groups were successfully synthesized via transesterification. Gel Permeation Chromatography (GPC) was used to characterize their molecular weight distributions; Fourier Transform Infrared Spectroscopy (FTIR) and solid-state Photoluminescence (PL) were employed to elucidate their structure-property relationships. Ultraviolet-Visible (UV-Vis) spectroscopy and fluorescence spectrophotometry were applied to investigate their AIE behavior under solvent concentration gradients, with a focus on luminescence mechanisms. The results showed a non-monotonic relationship between fluorescence intensity and the molecular weight (M<sub>w</sub>) of HBPSi derivatives: fluorescence intensity is enhanced with moderate M<sub>w</sub> elevation but reduced at excessively high M<sub>w</sub> due to molecular packing effects and acyloxy group rotation. Notably, as the volume fraction of CCl<sub>4</sub> reached the range that induces significant polymer aggregation, the intensities of both excitation peaks (266–294&#xa0;nm, UV region) and emission peaks (440–460&#xa0;nm, blue visible region) increased exponentially—this trend reflects the dependence of blue luminescence on polymer aggregation degree, supporting the proposed cluster-induced emission hypothesis. Consistent with FTIR spectral shifts and solvent-dependent PL behavior, we propose a mechanism hypothesis: the AIE of these derivatives originates from the synergy of “non-conjugated functional group clusters” in the polymers. Cluster-induced electronic delocalization and intramolecular charge transfer (ICT) between C=C and acyloxy groups may facilitate exciton radiative transitions, while the 3D hyperbranched spatial hindrance restricts excessive intermolecular aggregation—collectively suppressing non-radiative transition pathways.</p> Graphical abstract <p></p>

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Synthesis, characterization and aggregation-induced emission mechanism of AIE-active hyperbranched polysiloxane derivatives with C=C and acyloxy groups

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • Yuan Jia,
  • Ziyi Yang,
  • Juxiang Yang,
  • Beibei Li,
  • Zhen Liu

摘要

Hyperbranched polysiloxanes (HBPSi) are novel non-conjugated polymers with aggregation-induced emission (AIE) and modifiable terminals, and have attracted attention due to their unique topology and functional potential. In this study, two AIE-active HBPSi derivatives (OA-HBPSi and IBO-HBPSi, where OA stands for oleic acid and IBO stands for isobutyric acid) containing C=C and acyloxy groups were successfully synthesized via transesterification. Gel Permeation Chromatography (GPC) was used to characterize their molecular weight distributions; Fourier Transform Infrared Spectroscopy (FTIR) and solid-state Photoluminescence (PL) were employed to elucidate their structure-property relationships. Ultraviolet-Visible (UV-Vis) spectroscopy and fluorescence spectrophotometry were applied to investigate their AIE behavior under solvent concentration gradients, with a focus on luminescence mechanisms. The results showed a non-monotonic relationship between fluorescence intensity and the molecular weight (Mw) of HBPSi derivatives: fluorescence intensity is enhanced with moderate Mw elevation but reduced at excessively high Mw due to molecular packing effects and acyloxy group rotation. Notably, as the volume fraction of CCl4 reached the range that induces significant polymer aggregation, the intensities of both excitation peaks (266–294 nm, UV region) and emission peaks (440–460 nm, blue visible region) increased exponentially—this trend reflects the dependence of blue luminescence on polymer aggregation degree, supporting the proposed cluster-induced emission hypothesis. Consistent with FTIR spectral shifts and solvent-dependent PL behavior, we propose a mechanism hypothesis: the AIE of these derivatives originates from the synergy of “non-conjugated functional group clusters” in the polymers. Cluster-induced electronic delocalization and intramolecular charge transfer (ICT) between C=C and acyloxy groups may facilitate exciton radiative transitions, while the 3D hyperbranched spatial hindrance restricts excessive intermolecular aggregation—collectively suppressing non-radiative transition pathways.

Graphical abstract