Multicolor emissive hyperbranched polysiloxanes from enhanced spatial electronic communication for security encryption and bacteria imaging

Unconventional fluorescent polymers with long-wavelength emission have attracted considerable attention due to their facile preparation, good biocompatibility, and excellent processability. However, their emission at long-wavelength is relative low. Herein, a series of aromatic amino acids functionalized hyperbranched polysiloxanes with deep red to cyan fluorescence were prepared. Experimental and theoretical calculation results show that the long-wavelength emission comes from the spatial electronic delocalization among conjugated π bonds and electron-rich functional groups. The balance between rigidity and flexibility is favorable for the strong long-wavelength emission. Moreover, the polymers’ fluorescence is sensitive to Fe³⁺ and OH^– ions; and these polymers show potential applications in security encryption, fluorescent stamp inks and bacteria multicolor fluorescence imaging. This work provides an efficient method for the development of long-wavelength emissive unconventional fluorescence polymers.