Semiperfluoroalkyl Polyfluorenes for Orthogonal Processing in Fluorous Solvents

Ultratrace PFAS Detection Using Amplifying Fluorescent Polymers

Per- and poly(fluoroalkyl) substances (PFAS) are environmentally persistent pollutants that are of growing concern due to their detrimental effects at ultratrace concentrations (ng·L^-1) in human and environmental health. Suitable technologies for on-site ultratrace detection of PFAS do not exist and current methods require complex and specialized equipment, making the monitoring of PFAS in distributed water infrastructures extremely challenging. Herein, we describe amplifying fluorescent polymers (AFPs) that can selectively detect perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of ng·L^-1. The AFPs are highly fluorinated and have poly(p-phenylene ethynylene) and polyfluorene backbones bearing pyridine-based selectors that react with acidic PFAS via a proton-transfer reaction. The fluorinated regions within the polymers partition PFAS into polymers, whereas the protonated pyridine units create lower-energy traps for the excitons, and emission from these pyridinium sites results in red-shifting of the fluorescence spectra. The AFPs are evaluated in thin-film and nanoparticle forms and can selectively detect PFAS concentrations of ∼1 ppb and ∼100 ppt, respectively. Both polymer films and nanoparticles are not affected by the type of water, and similar responses to PFAS were found in milliQ water, DI water, and well water. These results demonstrate a promising sensing approach for on-site detection of aqueous PFAS in the ng·L^-1 range.

Fluorinated Poly(aryl piperidinium) Membranes for Anion Exchange Membrane Fuel Cells

Anion-exchange-membrane fuel cells (AEMFCs) are a cost-effective alternative to proton-exchange-membrane fuel cells (PEMFCs). The development of high-performance and durable AEMFCs requires highly conductive and robust anion-exchange membranes (AEMs). However, AEMs generally exhibit a trade-off between conductivity and dimensional stability. Here, a fluorination strategy to create a phase-separated morphological structure in poly(aryl piperidinium) AEMs is reported. The highly hydrophobic perfluoroalkyl side chains augment phase separation to construct interconnected hydrophilic channels for anion transport. As a result, these fluorinated PAP (FPAP) AEMs simultaneously possess high conductivity (>150 mS cm^-1 at 80 °C) and high dimensional stability (swelling ratio <20% at 80 °C), excellent mechanical properties (tensile strength >80 MPa and elongation at break >40%) and chemical stability (>2000 h in 3 m KOH at 80 °C). AEMFCs with a non-precious Co-Mn spinel cathode using the present FPAP AEMs achieve an outstanding peak power density of 1.31 W cm^-2 . The AEMs remain stable over 500 h of fuel cell operation at a constant current density of 0.2 A cm^-2 .

Improving the Electropolymerization Properties of Fluorene-Bridged Dicarbazole Monomers through Polyfluoroalkyl Side Chains

The facile functionalization of the fluorene scaffold at the 2,7-positions was utilized to provide access to two soluble carbazole-π-carbazole derivatives CFC-H1 and CFC-F1 featuring fully hydrogenated and polyfluorinated alkyl chains at the 9-position of the fluorene π-bridging unit, respectively. The optical and electrochemical properties of the new dicarbazoles were investigated. Their electrochemical polymerization over Pt and indium tin oxide electrodes allowed the generation of electroactive polymeric films, whose physicochemical characteristics were strongly dependent on the kind of alkyl chain present on the fluorene bridge. In particular, the electropolymerization of the polyfluorinated monomer allowed the fabrication of thin films with good electrical conductivity, reversible electrochemical processes, good electrochromic properties, and enhanced water repellency with respect to its nonfluorinated analogue.

Universal Route to Impart Orthogonality to Polymer Semiconductors for Sub-Micrometer Tandem Electronics

A universal method that enables utilization of conventional photolithography for processing a variety of polymer semiconductors is developed. The method relies on imparting chemical and physical orthogonality to a polymer film via formation of a semi-interpenetrating diphasic polymer network with a bridged polysilsesquioxane structure, which is termed an orthogonal polymer semiconductor gel. The synthesized gel films remain tolerant to various chemical and physical etching processes involved in photolithography, thereby facilitating fabrication of high-resolution patterns of polymer semiconductors. This method is utilized for fabricating tandem electronics, including pn-complementary inverter logic devices and pixelated polymer light-emitting diodes, which require deposition of multiple polymer semiconductors through solution processes. This novel and universal method is expected to significantly influence the development of advanced polymer electronics requiring sub-micrometer tandem structures.

Electroluminescence from Solution-Processed Pinhole-Free Nanometer-Thickness Layers of Conjugated Polymers

We report the formation of robust, reproducible, pinhole-free, thin layers of fluorinated polyfluorene conjugated copolymers on a range of polymeric underlayers via a simple solution processing method. This is driven by the different characters of the fluorinated and nonfluorinated sections of these polymers. Photothermal deflection spectroscopy is used to determine that these layers are 1-2 nm thick, corresponding to a molecularly thin layer. Evidence that these layers are continuous and pinhole-free is provided by electroluminescence data from polymer LED devices that incorporate these layers within the stacked LED structure. These reveal, remarkably, light emission solely from these molecularly thin layers.

Enabling high-mobility, ambipolar charge-transport in a DPP-benzotriazole copolymer by side-chain engineering

In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit.

In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit. We demonstrate that the BTZ unit allows for additional solubilizing side-chains on the co-monomer and show that the introduction of a linear side-chain on the DPP-unit leads to an increase in thin-film order and charge-carrier mobility if a sufficiently solubilizing, branched, side chain is attached to the BTZ. We compare two different synthetic routes, direct arylation and Suzuki-polycondensation, by a direct comparison of polymers obtained via the two routes and show that direct arylation produces polymers with lower electrical performance which we attribute to a higher density of chain Furthermore we demonstrate that a polymer utilizing this design motif and synthesized via Suzuki-polycondensation ((l-C₁₈)-DPP-(b-C₁₇)-BTZ) exhibits exceptionally high and near balanced average electron and hole mobilities >2 cm² V^–1 s^–1 which are among the highest, robustly extracted mobility values reported for DPP copolymers in a top-gate configuration to date. Our results demonstrate clearly that linear side chain substitution of the DPP unit together with co-monomers that allow for the use of sufficiently long or branched solubilizing side chains can be an attractive design motif for solution processable, high mobility DPP copolymers.

Fluorous-inorganic hybrid dielectric materials for solution-processed electronic devices

Fluorous-inorganic hybrid dielectric (FIHD) materials in fluorous solvents can be deposited on top of organic semiconductor films by solution casting.

White polymer light-emitting devices for solid-state lighting: materials, devices, and recent progress

White polymer light-emitting devices (WPLEDs) have become a field of immense interest in both scientific and industrial communities. They have unique advantages such as low cost, light weight, ease of device fabrication, and large area manufacturing. Applications of WPLEDs for solid-state lighting are of special interest because about 20% of the generated electricity on the earth is consumed by lighting. To date, incandescent light bulbs (with a typical power efficiency of 12-17 lm W(-1) ) and fluorescent lamps (about 40-70 lm W(-1) ) are the most widely used lighting sources. However, incandescent light bulbs convert 90% of their consumed power into heat while fluorescent lamps contain a small but significant amount of toxic mercury in the tube, which complicates an environmentally friendly disposal. Remarkably, the device performances of WPLEDs have recently been demonstrated to be as efficient as those of fluorescent lamps. Here, we summarize the recent advances in WPLEDs with special attention paid to the design of novel luminescent dopants and device structures. Such advancements minimize the gap (for both efficiency and stability) from other lighting sources such as fluorescent lamps, light-emitting diodes based on inorganic semiconductors, and vacuum-deposited small-molecular devices, thus rendering WPLEDs equally competitive as these counterparts currently in use for illumination purposes.

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

Oligofluorene-functionalised truxenes containing perfluorohexylthiophene units at the terminal positions on the arms were synthesised, and their optical and electrochemical properties were investigated to determine the effect that the perfluorohexylthiophene unit has on the HOMO and LUMO properties of the oligomers. By synthesising a molecule with longer oligofluorene arms the effects of the perfluorohexylthiophene unit on larger oligomers was explored. The effect of steric hindrance from the perfluorohexyl chain was also evaluated by altering the position of the chain on the thiophene moiety.

Orthogonal patterning of multiple biomolecules using an organic fluorinated resist and imprint lithography

The ability to spatially deposit multiple biomolecules onto a single surface with high-resolution while retaining biomolecule stability and integrity is critical to the development of micro- and nanoscale biodevices. While conventional lithographic patterning methods are attractive for this application, they typically require the use of UV exposure and/or harsh solvents and imaging materials, which may be damaging to fragile biomolecules. Here, we report the development of a new patterning process based on a fluorinated patterning material that is soluble in hydrofluoroether solvents, which we show to be benign to biomolecules, including proteins and DNA. We demonstrate the implementation of these materials into an orthogonal processing system for patterning multibiomolecule arrays by imprint lithography at room temperature. We further showcase this method's capacity for fabricating patterns of receptor-specific ligands for fundamental cell studies.

Completing the color palette with spray-processable polymer electrochromics

The field of electrochromic polymers has now reached an important milestone with the availability of a yellow to fully transmissive, cathodically coloring, solution-processable electroactive polymer. This is in addition to previously published electrochromic polymers that have neutral state colors that span from orange, red, magenta, blue, cyan, green, and black, that also attain highly transmissive states upon switching. With this, the full color palette is now complete allowing the largest variety of colors for transmissive and reflective electrochromic display applications. Here, we report on how we have been able to obtain this full color palette through synthetic modifications and color tuning utilizing electron rich and donor-acceptor repeat units, electron-donating substituents, and steric interactions with our 3,4-alkylenedioxythiophene family of polymers. Additionally, using solubilizing pendant groups for both organic and aqueous compatibility, we have been able to create this color palette with fully solution processable materials, paving the way for materials patterning, printing, and incorporation into devices for display and window applications.

Benzotriazole containing conjugated polymers for multipurpose organic electronic applications

Benzotriazole (BTz) containing polymers are reviewed from a general perspective in terms of their potential use in organic electronic applications namely electrochromics (ECs), organic solar cells (OSCs) and organic light emitting diodes (OLEDs) in comparison with the structurally similar polymers.