Pyrene-Decorated Thermally Responsive Luminescent Nanoparticles: The Effect of Copolymer Micelle Morphology

Pyrene and its derivatives are widely utilized for their fluorescent behavior, and excimer formation allows the study of molecular structural behavior. Hence, it was hypothesized that surface-decorated block copolymer nano-objects would make suitable materials for studying such interactions. Pyrene-decorated polymer nano-objects were successfully synthesized through reversible addition–fragmentation chain-transfer (RAFT)-mediated polymerization-induced self-assembly (PISA). Specifically, various morphologies (spheres, worms, and vesicles) of pyrene-functionalized poly(glycerol methacrylate-b-hydroxypropyl methacrylate) (Py-P(GMA-b-HPMA)) were prepared by precisely controlling the degree of polymerization of the core-forming PHPMA block and temperature. These pyrene-functionalized nano-objects were used to study the influence of morphology on their photoluminescent behavior by comparing the emission intensity ratio between pyrene excimers (Ie) and monomers (Im). It was found that with increasing particle size or transitioning to higher-order morphologies, Ie/Im increased due to lower surface curvature. Thus, pyrene end-functional block copolymers serve as useful fluorescent probes to investigate changes in nanoparticle morphology and aggregation.