Fluorescence emission from hyperbranched polycarbonate without conventional chromohpores

Fluorescent polymers without non-conventional luminescent units have attracted great attention due to their excellent biocompatible. In this paper, we fabricated a kind of nonconjugated hyperbranched polycarbonate (HBPC) through one-pot transesterification method using diethyl carbonate and trimethylolpropane under solvent and catalyst-free condition. Unexpectedly, the HBPC can exhibit bright blue photoluminescence without any treatment under a 365 nm UV light. The results show that the fluorescence of HBPC in ethanol displays the excitation- and concentration-dependent behaviors. In addition, its fluorescence exhibits an aggregation-enhanced emission (AEE) effect in water-ethanol system. The fluorescence emission behaviors of HBPC can be well rationalized by the clustering-induced emission (CIE) mechanism. In other words, the fluorescence is caused by the electron cloud overlap within the clustering of carbonate groups. The TEM images further reveal that the rigidity conformation of HBPC was formed in the higher concentration because of the existence of hydrogen bonds. Besides, the ball and stick model firstly simulates the HBPC emission behavior.