Enhanced Brightness Emission-Tuned Nanoparticles from Heterodifunctional Polyfluorene Building Blocks

Abstract

Three-coordinate complexes (bromo)[4-(2,2-dimethyl-1,3-dioxolan-4-yl)-phenyl](tri-tert-butyl-phosphine)palladium (1) and (bromo){4-[(tetrahydro-2H-pyran-2-yloxy)methyl]phenyl}(tri-tert-butyl-phosphine)palladium (2) were used to initiate Suzuki-Miyaura chain growth polymerization of 7'-bromo-9',9'-dioctyl-fluoren-2'-yl-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane (3). The polymerization was optionally terminated by end-capping with red-emitting N-(2-ethylhexyl)-1,6-bis(4-tert-octylphenoxy)-9-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-perylene-3,4-dicarboximide. Heterodisubstituted polyfluorenes of adjustable molecular weights between 5 × 10(3) and 1.0 × 10(4) g mol(-1) and narrow molecular weight distribution (M(w)/M(n) < 1.2), bearing precisely one or two hydroxyl groups on one chain end and optionally a dye-label on the opposite end, were obtained virtually devoid of any side-products. Covalent attachment of polyethylene glycol (M(n) = 2 × 10(3) g mol(-1)) to the reactive end groups yielded amphiphilic block copolymer, which afforded stable nanoparticles with diameters in the range of 25-50 nm when dispersed in water. These particles exhibited a bright fluorescence emission with quantum yields as high as Φ = 84%, which could optionally be tuned to longer wavelengths by energy transfer to the perylene monoimide dye. The heterodifunctional nature of these polyfluorenes is crucial for a bright and enduring fluorescence brightness as revealed by comparison to nanoparticles containing physically mixed dye. Further addition of terrylene diimide dye to the nanoparticles of perylene-end-capped polyfluorene block copolymers allows for an energy cascade resulting in emission exclusively in the deep red and near-infrared regime.

Pd- and Ni-catalyzed cross-coupling reactions in the synthesis of organic electronic materials

“…These compounds are frequently synthesized by the Pd-catalyzed polycondensation of AA and BB monomers. The exceptional physical properties of polyphenylenes and related compounds have supported the development of organic electronic materials that are highly processable [80, 92, 93]. …”

Intrinsically Fluorescent, Stealth Polypyrazoline Nanoparticles with Large Stokes Shift for In Vivo Imaging

“…Common amphiphilic architectures and corresponding core–shell nanoparticles for in vivo drug delivery and imaging employ poly(ethylene glycol) (PEG) as a protein repellent and hydrophilic shell . However, few intrinsically fluorescent polymers have been incorporated into such composite NPs . We therefore envisioned that PEG‐ block ‐PPy copolymers could be interesting candidates to generate colloidal imaging probes.…”

Intramolecular charge-transfer emission from conjugated polymer nanoparticles: the terminal group effect on electronic and optical properties

“…Many efforts have been devoted to the modification of CPNs for improving their colloidal stabilities and bioconjugation abilities. [27][28][29][30][31][32][33][34][35] The FRET between the CPN core and the terminal units can be sensitive to the presence of analytes, and the fluorescence color and/or intensity can thus be used for detection. In fact, almost all fluorescent tunable CPNs are realized through fluorescence resonance energy transfer (FRET) from energy donors (conjugated polymers) to acceptors (dopants).…”