Synthesis of phosphaphenanthrene-containing 4-ethynylbenzonate grafted glycidyl azide polymers by click chemistry and their aggregation-induced emission enhancement properties

Phosphaphenanthrene-containing 4-ethynylbenzonate (MAT4) was grafted to glycidyl azide polymer (GAP) by click chemistry in the presence of Cul as catalyst. FT-IR analytical results confirmed the structure of the grafting polymer (G-M4) and revealed the click reaction between GAP and MAT4 in equal molar ratio. Compared with MAT4, the UV-Vis absorbance and the photoluminescence strength of G-M4 in dichloromethylene solution are obviously increased because the formation of triazole induces the increasing of total conjugated degree. When G-M4 molecules aggregate to a certain degree in a mixture of dichloromethylene and n-hexane, the photoluminescence strength of G-M4 proportionally increases, which shows obvious aggregation-induced emission enhancement (AIEE) property because the aggregation state of G-M4 restricts the intramlecular rotation of phosphaphenanthrene groups based on the TT-TT stacking and polarity interaction between the molecules. Due to J-aggregation, supramolecular structure between triazole rings in G-M4 and phosphaphenanthrene groups in adjacent G-M4 based on donor-accept interaction is formed. When the content of ra-hexane is over 70%, the photoluminescence spectra of G-M4 obviously show two peaks, which are attributed to photoluminescence emission of intra-and extra-chains of G-M4, respectively. This novel phenomenon may enable the polymer to find applications in chemosensor, optical display and rewritable optical media.