Anisotropic Polymer Nanoparticles with Tunable Emission Wavelengths by Intersegmental Chain Packing

Julian D. Ruiz Perez and Stefan Mecking Angew. Chem. Int. Ed. 2017, 56, 6147 –6151 DOI: 10.1002/anie.201701000

Abstract: The shape of nanoparticles is decisive for their selfassembly properties, as well as for the behavior of individual particles in many instances. The introduction and control of anisotropy is well-known for inorganic nanocrystals but a largely unresolved problem for polymer nanoparticles, especially for conjugated polymers. Here, we report a reproducible preparation method using heterophase polymerization for a range of stable dispersions of ellipsoidal conjugated polymer nanoparticles with sizes in the range of 50 to 180 nm and narrow size and shape distributions. The nanoparticles show a bright fluorescence with tunable emission wavelengths and quantum yields as high as φ=78%. Structural investigations reveal the nanoparticles to be composed of a highly ordered β- and α’-phase within a nematic matrix. Preliminary studies on the origin of particle  anisotropy suggest a concerted mechanism in which anisotropic shape evolves from intersegmental packing that occurs along with progressing chain formation by polymerization.