A facile strategy to modulate the fluorescent properties of star polymers by varying the arm numbers

A simple approach to tune the fluorescent properties of star polymers was reported via only adjusting the arm numbers. Atom transfer radical polymerization (ATRP) using β-CD-based initiators was utilized to synthesize star-shaped poly(N-vinyl carbazole) (star PVK) consisting of β-cyclodextrin (β-CD) core and different arm numbers (3, 7, and 14). The conversion ratio was nearly 100 % characterized by 1H-NMR. Fluorescent properties of star PVKs could be modulated by varying the arm number at the same mass concentration of fluorescent groups. Fluorescence intensity declined with the increase of arm number and displayed “sandwich-like excimer” emission rather than “higher-energy excimer” emission. The unique structure of star polymer might effectively inhibit the formation of “random coil”, which often happened in linear polymer systems. In addition, all of the star PVKs with different arm numbers had the same emission peak centered at 395 nm and excimer band at 420 nm, respectively, which differed from their linear counterparts and demonstrated that the intramolecular interaction was not dominant in this system.