The inherent blue luminescence from oligomeric siloxanes

Luminescent polymers without traditional aromatic groups have attracted great attention due to their excellent biocompatibility and promising applications. Understanding of the luminescence mechanism of such polymers, however, is still in its infancy. To further reveal the fluorescence mechanism in depth, two kinds of oligomeric siloxanes were skillfully elaborated and fabricated via a convenient and facile one-pot transesterification polycondensation reaction under catalyst-free conditions. Intriguingly, oligomeric siloxanes bearing nonconventional chromophores show bright blue fluorescence under 365 nm UV lamp illumination. Our preliminary results demonstrate that oxygen clusters, namely, clustering-triggered emission (CTE), can well explain the inherent fluorescence of oligomeric siloxanes. Moreover, intermolecular hydrogen bonds are conducive to the aggregation of the molecular chains. Then, these bonds will facilitate the formation of oxygen clusters, which produce electron cloud overlap to form the unusual chromophores. In addition, the results suggest that the fluorescence intensity of oligomeric siloxanes enhances with increasing concentration. Furthermore, excitation-dependent emission behavior is observed when varying the excitation wavelength of oligomeric siloxanes. It is also found that the luminescence of oligomeric siloxanes could be effectively tuned by the solvent and metal ions.