Sulfonium-cation-containing aggregation-induced emission block copolymers: self-assembly, multicolor emission, and detection for DNA polyplexes

•Amphiphilic block copolymers containing sulfonium cations and a tetraphenylethene unit were synthesized.•These block copolymers exhibit unique self-assembly properties with aggregation-induced emission (AIE) in water.•By introducing charged fluorescent dyes, the emission color was changed from blue to orange/red.•The emission color and intensity were governed by polyplex formation with negatively charged DNA.•This system provides a method for efficient visual detection of DNA polyplex formation and DNA quantification.