The shape of nanoparticles is decisive for their self-assembly 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.

Synthetic polymers are mixtures of chains with different lengths, and their chain length and chain conformation are often experimentally characterized by ensemble averages. We demonstrate that double electron–electron resonance (DEER) spectroscopy can reveal the chain length distribution and the chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki–Miyaura coupling polymerization. The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain-terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation, and flexibility can also be accessed within poly­(fluorene) nanoparticles.

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 f = 78 %. Structural investigations reveal the nanoparticles to be composed of a highly ordered b-and a'-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.

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.

Synthetic polymers are mixtures of different length chains, and their chain length and chain conformation is often experimentally characterized by ensemble averages. We demonstrate that Double-Electron-Electron-Resonance (DEER) spectroscopy can reveal the chain length distribution, and chain conformation and flexibility of the individual n-mers in oligo-(9,9-dioctylfluorene) from controlled Suzuki-Miyaura Coupling Polymerization (cSMCP). The required spin-labeled chain ends were introduced efficiently via a TEMPO-substituted initiator and chain terminating agent, respectively, with an in situ catalyst system. Individual precise chain length oligomers as reference materials were obtained by a stepwise approach. Chain length distribution, chain conformation and flexibility can also be accessed within poly(fluorene) nanoparticles.