Improving the Kumada Catalyst Transfer Polymerization with Water-Scavenging Grignard Reagents

Conjugated polymers have received widespread interest as optoelectronic materials. Recently, these macromolecules have been adopted for biologically relevant applications, such as sensors, imaging agents, and drug delivery vectors. A major limitation of the chemistry used to prepare these classes of compounds is that the resultant polymers themselves are not tolerant to water or are not inherently water-soluble. For example, the most controlled method of conjugated polymer synthesis, the Kumada catalyst transfer polymerization (KCTP), requires stringent drying of monomers, catalysts, and other reagents. Here, we describe an approach to use a water-scavenging Grignard reagent to alleviate many of the shortcomings that currently hinder the synthesis of water-soluble conjugated polymers. This method shows improved polymerization performance in both traditional conjugated polymer synthesis as well as more challenging syntheses of polar hygroscopic polymers that are of interest for biological applications.

Mechanically Induced Conformation Change, Fluorescence Modulation, and Mechanically Assisted Photodegradation in Single Nanoparticles of the Conjugated Polymer Poly(9,9-dioctylfluorene)

We explored the possibility of nanoscale mechanical manipulation and control of photophysical properties of conjugated polymer nanoparticles. We carried out a simultaneous atomic force microscopy (AFM) and fluorescence microspectroscopy study on single nanoparticles of the conjugated polymer poly(9,9-dioctylfluorene). The nanoparticles are prepared by a reprecipitation method and have an average height of 27 nm, and their emission is dominated by the well-ordered β-phase conformation. Fluorescence polarization anisotropy and numerical simulations show that each particle contains at least three partly oriented straight β-phase segments surrounded by amorphous glass-phase polyfluorene chains. In the simultaneous experiments, an AFM tip was used to apply external force on a single nanoparticle, and a confocal fluorescence microscope was used to monitor in real time the resulting changes in the fluorescence intensity and spectra. In a nitrogen atmosphere, weak to moderate force of up to 1 μN acts mainly on the glass-phase polyfluorene chains by forming quenchers that cause an efficient and reversible fluorescence decrease, whereas the β-phase segments stay unaffected. A higher force of 5 μN, on the contrary, breaks the β-phase segments into multiple glass-phase segments, causing a net increase in fluorescence intensity. Under ambient air conditions, even a moderate force of 1 μN strongly accelerates the degradation of the nanoparticle by preferably photobleaching the β-phase and partially transforming it into the glass phase. These results will contribute to the fundamental knowledge on the relationship between photophysical and structural properties of polyfluorene nanostructures, and will also provide important feedback for potential applications of such nanostructures in flexible optoelectronic devices.

Molecular Engineering and Design of Semiconducting Polymer Dots with Narrow-Band, Near-Infrared Emission for in Vivo Biological Imaging

This article describes the design and synthesis of donor-bridge-acceptor-based semiconducting polymer dots (Pdots) that exhibit narrow-band emissions, ultrahigh brightness, and large Stokes shifts in the near-infrared (NIR) region. We systematically investigated the effect of π-bridges on the fluorescence quantum yields of the donor-bridge-acceptor-based Pdots. The Pdots could be excited by a 488 or 532 nm laser and have a high fluorescence quantum yield of 33% with a Stokes shift of more than 200 nm. The emission full width at half-maximum of the Pdots can be as narrow as 29 nm, about 2.5 times narrower than that of inorganic quantum dots at the same emission wavelength region. The average per-particle brightness of the Pdots is at least 3 times larger than that of the commercially available quantum dots. The excellent biocompatibility of these Pdots was demonstrated in vivo, and their specific cellular labeling capability was also approved by different cell lines. By taking advantage of the durable brightness and remarkable stability of these NIR fluorescent Pdots, we performed in vivo microangiography imaging on living zebrafish embryos and long-term tumor monitoring on mice. We anticipate these donor-bridge-acceptor-based NIR-fluorescent Pdots with narrow-band emissions to find broad use in a variety of multiplexed biological applications.

Conjugated Polymer Nanoparticle-Triplet Emitter Hybrids in Aqueous Dispersion: Fabrication and Fluorescence Quenching Behavior

Conjugated polymer nanoparticles based on poly[9,9-bis(2-ethylhexyl)fluorene] and poly[N-(2,4,6-trimethylphenyl)-N,N-diphenylamine)-4,4'-diyl] are fabricated using anionic surfactant sodium dodecylsulphate in water by miniemulsion technique. Average diameters of polyfluorene and polytriarylamine nanoparticles range from 70 to 100 and 100 to 140 nm, respectively. The surface of the nanoparticles is decorated with triplet emitting dye, tris(2,2'-bipyridyl)ruthenium(II) chloride. Intriguing photophysics of aqueous dispersions of these hybrid nanoparticles is investigated. Nearly 50% quenching of fluorescence is observed in the case of dye-coated polyfluorene nanoparticles; excitation energy transfer is found to be the dominant quenching mechanism. On the other hand, nearly complete quenching of emission is noticed in polytriarylamine nanoparticle-dye hybrids. It is proposed that the excited state electron transfer from the electron-rich polytriarylamine donor polymer to Ru complex leads to the complete quenching of emission of polytriarylamine nanoparticles. The current study offers promising avenues for developing aqueous solution processed-electroluminescent devices involving a conjugated polymer nanoparticle host and Ru or Ir-based triplet emitting dye as the guest.

Synthesis of Water-Soluble Iridium (III)-Containing Nanoparticles for Biological Applications

Water-soluble nanoparticles (Ir/PGlc-NP, Ir/β-1,3-glucan-NP) based on water-soluble glycopolymers (PGlc),β-1,3-glucan polysaccharide, and conjugated phosphorescent Ir (III) complexes were successfully synthesized by self-assembly. The obtained nanoparticles have good spherical morphological characterization with a mean diameter of 50 nm measured by TEM. Ir/PGlc-NP and Ir/β-1,3-glucan-NP showed the same emission maxima at 565 nm in aqueous solution and both caused effective apoptosis and death of HepG2 and Hela cells after being irradiated at 445 nm for 30 min in vitro. Fluorescence cellular imaging was conducted by confocal laser scanning microscopy (CLSM) using HepG2 cells as the model cell in which the nanoparticles had successfully entered into the cytoplasm with high brightness. Furthermore, after injecting the nanoparticles into live mice in vivo, the real-time fluorescence imaging as well as the nanoparticles distribution in organs at 24 hours after administration indicated that these nanoparticles can serve as fluorescent imaging contrast for further biological applications.

A single-step emulsion approach to prepare fluorescent nanoscale coordination polymers for bioimaging

A facile and convenient microemulsion method is demonstrated to prepare fluorescent nanoscale coordination polymers. And the nanoscale coordination polymers exhibited bright blue fluorescence and good biocompatibility, thus giving them the ability for bioimaging.