Nonconjugated Polyesters Emitting Full-Color Clusteroluminescence

Photoluminescent polymers have been attracting great attention, owing to their intrinsic mechanical properties, diverse structures, and the ability of intra/inter-chain interactions to regulate their luminescent properties. Conventional luminescent polymers contain classical luminophores, such as extended π-conjugated aromatic carbocyclic and heterocyclic groups, which could emit multicolor photoluminescence (PL) but suffer from biotoxicity, poor processability, complicated synthesis, and environmental hazards. In recent decades, heteroatom (e.g., O, N)-rich nonconjugated polymers without classical luminophores have been revealed to exhibit abnormal photoluminescence, namely, clusteroluminescence (CL), originating from through-space electronic interaction between heteroatomic groups. These newly discovered heteroatomic polymers take advantage of low cost, mass production, processability, and biocompatibility. Therefore, developing full-color CL polymers and revealing their unique PL mechanisms are highly desired in chemistry, biology, and material science.

In this Account, we summarize our research on nonconjugated polyester for high-efficiency full-color CL via structure-driven through-space (n, π*) interaction (TSI-(n, π*)), as a new paradigm for designing nonconjugated CL polymers with deeper insight into CL, including the molecular design of polyesters, the structure–luminescence relationship, and mechanism. This Account starts with a brief introduction to the recent development of CL in heteroatom-rich polymers as well as polyesters containing n and π electrons as one of the classical CL polymers. Then, we discuss the synthetic methods of polyesters based on the polymerization-induced emission (PIE) strategy, transforming nonluminescent monomer into luminescent polyester, or achieving red shifts in the emission wavelength through multiple through-space electronic interactions from polymer hierarchical structures. The third part summarizes the regulation of CL properties (wavelength and efficiency) by altering TSI-(n, π*) relying on hierarchical structures (segmental structures, conformation, end-group structures, and electronic bridge structures) of polyesters, achieving high-efficiency full-color CL (400–800 nm) from blue to near-infrared (NIR). We then proposed subnanometer TSI-(n, π*) and photomodulated through-space electronic coupling in polyesters for CL mechanism and provided an outlook on the development of CL polyester materials and applications.