Colorful Luminescence of Conjugated Polyelectrolytes Induced by Molecular Weight

Due to their distinctive intrinsic advantages, the nanoaggregates of conjugated polyelectrolytes (CPEs) are fascinating and attractive for various luminescence applications. Generally, the emission luminescence of CPEs is determined by the conjugated backbone structure, i.e., different conjugated backbones of CPEs produce emission luminescence with different emission wavelength bands. Here, we polymerized the bis(boronic ester) of benzothiadiazole and an alkyl sulfonate sodium-substituted dibromobenzothiatriazole to provide PBTBTz-SO(3)Na with different molecular weights via controlling the ratio of the monomer and the catalyst. Theoretically, the CPEs with the same molecular structure usually display similar photoelectronic performances. However, the resulting PBTBTz-SO(3)Na reveal a similar light absorption property, but different luminescence. The higher molecular weight is, the stronger the fluorescence intensity of PBTBTz-SO(3)Na that occurs. PBTBTz-SO(3)Na with different molecular weights have different colors of luminescence. It is well known that the molecular aggregates often led to weaker luminescent properties for most of the conjugated polymers. However, PBTBTz-SO(3)Na exhibits a higher molecular weight with an increasing molecular chain aggregation, i.e., the nanoaggregates of PBTBTz-SO(3)Na are beneficial to emission luminescence. This work provides a new possible chemical design of CPEs with a controllable, variable luminescence for further optoelectronics and biomedicine applications.