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Crosslinking of semiconductors is critical towards building heterostructures to enable flexibility in the design of devices. Bis(fluorophenyl azide)s (FPAs) and their sterically-substituted derivatives (sFPAs) have been demonstrated to be able to photo-crosslink semiconductor polymers upon deep-UV exposure, stabilizing their morphologies in devices. Here, we report the development of both UV (254 nm) and i-line (365 nm) photo-activatable FPA and sFPA – FPA80 and sFPA82 – both incorporating 3,5-bis(methylene)-1,1-dimethyl-4-piperidonium, a conjugation-extending bridge that also bears an ionic group. These materials are useful for generic photo-crosslinking of both conjugated and non-conjugated polyelectrolytes. Good thermal stability and solubility in polar organic solvents are obtained. Good film retention (>80%) can be achieved with a crosslinker loading of less than 10 wt/wt% for high-molecular polymers (Mw > 100k), superior to alkyl bisazides. The photo-crosslinking efficiency of ca. 20% in model polyelectrolytes is limited by the occlusion of ionic crosslinkers from the polymer matrix where the C–H insertion reaction occurs, hence suppressing photo-crosslinking efficiency.

This article provides an elaborate discussion of reports involving the development of latent fingerprints (LFPs) over the past decades with specific emphasis on the contribution of conjugated polymers (CPs) in the field of forensic science. CPs have been explored in the field of interdisciplinary sciences due to their widespread applications in the fields of imaging, chemical and biological sensors, electronic device, cancer therapeutics, etc. Even in the field of forensic sciences, these CP materials are in a continuous race with the existing technology and newer materials for the detection of fingerprint marks on various surfaces thus assisting in the unravelling of the precise identification of an individual suspect in modern criminology. Due to their excellent photophysical and chemical properties such as low toxicity, ease of functionalization, strong fluorescence emission, high quantum yield, and good optical stability, these CPs can lead to high resolution, and increased sensitivity and selectivity in the imaging of LFPs compared to those developed by traditional tedious methods. In this perspective, the challenges faced for LFP development and the role of various CPs including conjugated polyelectrolytes, polymer dots, and polymer nanoparticles are elaborately explained, thus, providing a systematic overview on techniques based on CPs as contrasting agents in the development of LFPs on various porous and nonporous substrates. There are various challenges pertaining to the development of LFPs on a multitude of surfaces which can be addressed by exploring materials with a suitable hydrophobic–hydrophilic balance and a receptor site for specific interactions with fingerprint components. The incorporation of this design principle has successfully led to the development of efficient platforms for rapid, onsite, intricate and unique LFP patterns on every kind of surface.

The synthesis of conjugated polymers with ionic substituents directly bound to their main chain repeat units is a strategy for generating strongly electron-accepting conjugated polyelectrolytes, as demonstrated through the synthesis of a series of ionic azaquinodimethane (iAQM) compounds. The introduction of cationic substituents onto the quinoidal para-azaquinodimethane (AQM) core gives rise to a strongly electron-accepting building block, which can be employed in the synthesis of ionic small molecules and conjugated polyelectrolytes (CPEs). Electrochemical measurements alongside theoretical calculations indicate notably low-lying LUMO values for the iAQMs. The optical band gaps measured for these compounds are highly tunable based on structure, ranging from 2.30 eV in small molecules down to 1.22 eV in polymers. The iAQM small molecules and CPEs showcase the band gap reduction effects of combining the donor-acceptor strategy with the bond-length alternation reduction strategy. As a demonstration of their utility, the iAQM CPEs so generated were used as active agents in photothermal therapy.

Battery electrodes are complex mesoscale systems comprising an active material, conductive agent, current collector, and polymeric binder. Although significant research on composite electrode materials for Li-ion batteries focuses on the design, synthesis, and characterization of the active particles, the binder component has been shown to critically impact stability and ensure electrode integrity during volume changes induced upon cycling. Herein, we explore the ability of water-soluble, carboxylated conjugated polymer binders to aid in electron and ion transport in magnetite-based anodes. Specifically, poly[3-(potassium-4-butanoate)thiophene] (PPBT) and a potassium carboxylate functionalized 3,4-propylenedioxythiophene (ProDOT)-based copolymer (WS-PE2) were investigated and evaluated against the control, potassium salt form of poly(acrylic acid) (PAA-K). When used in conjunction with a polyethylene glycol (PEG) surface coating for the magnetite active material, PPBT provided for overall improved electro...

The delocalization of electrons in conjugated polymers impacts their chain shape, affecting their local ordering, self-assembly, and ultimately charge transport. Conjugated polyelectrolytes introduce electrostatic interactions as a molecular design parameter to potentially tune chain rigidity by combining the π-conjugated polymer backbone with pendant ionic groups. In conventional polyelectrolytes, the self-repulsion of the bound charges induce extended rod-like chain configurations. Here, we leverage small-angle neutron scattering to measure the chain shapes of model conjugated polymers in dilute solution with controlled fractions of randomly distributed pendant charges. We find these model polythiophenes are semiflexible, with a persistence length of approximately 3 nm, regardless of charge fraction, suggesting the effective absence of electrostatic rigidity in conjugated polyelectrolytes. While the overall persistence length is negligibly impacted by pendant charges, optical spectroscopy indicates that the pendant charges increase the backbone torsion between thiophene rings without significantly impacting the π-conjugation length (the length of electron delocalization along a nearly planar backbone) in dilute solution. These results indicate the effective decoupling of the pendant ionic charges from the overall chain conformation with implications for solution processing of organic semiconductors.

Organic semiconductors for photocatalytic application have received wide attention recently. However, developing organic photocatalysts for highly efficient photocatalytic hydrogen evolution is a great challenge. Herein, we show highly efficient photocatalytic hydrogen evolution from a series of novel conjugated polyelectrolytes (CPEs) by modulating their interaction with co-catalysts. The water-soluble CPEs greatly enhance the photocatalytic performance with 50-fold improvement over that of their non-dissolved precursor conjugated polymer. More importantly, the photocatalytic activity of these CPEs can be optimized by regulating their interaction with Pt co-catalysts through molecular engineering on the side chain species and counterions of CPEs. The cationic CPEs perform better than anionic CPEs due to the robust interaction between quaternary ammonium side chains in cationic CPEs and Pt co-catalysts. It is found that the optimized interface contact between cationic CPEs and Pt co-catalysts can result in more efficient charge transfer and higher photocatalytic activity.

Manufacturing large-area devices through a low-cost and large batch printing technique is the key to the commercialization of organic solar cells (OSCs). However, the lack of printable anode interlayer (AIL) materials severely impedes the development of high-efficiency printed OSCs. Herein, we synthesize three p-type self-doped conjugated polyelectrolytes (CPEs), namely, PCP-B, PCP-2B, and PCP-3B, as printable AIL materials for fabricating high-performance and large-area OSCs. By increasing the number of benzene units in the polymer backbone, the work function of the CPEs was enhanced from 4.57 to 5.01 eV, and the optical transparency was also improved because of the enlarged polymer band gap. The improved photoelectronic properties as well as a good film-forming capacity make the PCP-3B an ideal AIL material to be processed by the printing technique. By using PCP-3B, a 1 cm2 printed device was fabricated in which all the functional layers, including the AIL, active layer, and cathode interlayer were processed by blade-coating, achieving a power conversion efficiency (PCE) of 9.67%. The PCE belongs to the highest efficiency at present for printable large-area OSCs, showing a promising prospect for the OSC mass production.

The evolution of conjugated polyelectrolytes (CPEs) that transduce analyte–receptor interactions into detectable fluorescent responses in complex aqueous environments is predicated on advancements in molecular design and improved synthetic accessibility. Here, we demonstrate a simple post-polymerization modification protocol, based on thiol–ene click chemistry, that results in the rapid installation of sodium sulfate terminated side-chains to a poly(fluorene-co-ethynyl) scaffold. The fluorescence of the resulting water-soluble CPE is quenched by Fe3+, dequenched selectively by pyrophosphate (PPi), and accurately quantifies PPi within ±6 nM in artificial seawater. The broad utility of thiol–ene click chemistry should offer the straightforward integration of diverse sensing elements.

Electrostatic assembly of conjugated polyelectrolytes, which combine a π-conjugated polymer backbone with pendant ionic groups, offer an opportunity for tuning materials properties and a new route for formulating concentrated inks for printable electronics. Complex coacervation, a liquid-liquid phase separation upon complexation of oppositely charged polyelectrolytes in solution, is used to form dense suspensions of π-conjugated material. A model system of a cationic conjugated polyelectrolyte poly(3-[6'-{

Several donor–acceptor type conjugated polyelectrolytes containing naphthalimide are developed. Different polymer chain configurations of the backbones of polymers lead to different photophysical properties. The para-substituted polymers show extended conformations with quite low quantum yields in high polarity solvents because of twisted intramolecular charge transfer features, while the meta-substituted polymers can form helices and demonstrated significantly improved quantum yields in water and methanol, as well as achieving sensitive, ultrafast and ratiometric detection of trace methylene blue in water. Ministry of Education (MOE) Nanyang Technological University The authors would like to thank the National Natural Science Foundation of China (No. 21572115) and Shenzhen Municipal Government (JCYJ20170817161303009) for financial support. Dr Y. Lu is thankful for the financial support from NTU, Singapore (MOE Tier 1 grant RG116/15).

Polymer solar cells (PSCs) based on non-fullerene acceptors have the advantages of synthetic versatility, strong absorption ability, and high thermal stability. These characteristics result in impressive power conversion efficiency values, but to further push both the performance and the stability of PSCs, the insertion of appropriate interlayers in the device structure remains mandatory. Herein, a naphthalene diimide-based cathode interlayer (NDI-OH) is synthesized with a facile three-step reaction and used as a cathode interlayer for fullerene and non-fullerene PSCs. This cationic polyelectrolyte exhibited good solubility in alcohol solvents, transparency in the visible range, self-doping behavior, and good film forming ability. All these characteristics allowed the increase in the devices’ power conversion efficiencies (PCE) both for fullerene and non-fullerene-based PSCs. The successful results make NDI-OH a promising cathode interlayer to apply in PSCs.

The current Covid-19 Pandemic caused by the highly contagious SARS-CoV-2 virus has proven extremely difficult to prevent or control. Currently there are few treatment options and very few long-lasting disinfectants available to prevent the spread. While masks and protective clothing and “social distancing” may offer some protection, their use has not always halted or slowed the spread. Several vaccines are currently undergoing testing; however there is still a critical need to provide new methods for inactivating the virus before it can spread and infect humans. In the present study we examined the inactivation of SARS-CoV-2 by synthetic conjugated polymers and oligomers developed in our laboratories as antimicrobials for bacteria, fungi and non-enveloped viruses. Our results show that we can obtain highly effective light induced inactivation with several of these oligomers and polymers including irradiation with near-UV and visible light. With both the oligomers and polymers, we can reach several logs of inactivation with relatively short irradiation times. Our results suggest several applications involving the incorporation of these materials in wipes, sprays, masks and clothing and other Personal Protection Equipment (PPE) that can be useful in preventing infections and the spreading of this deadly virus and future outbreaks from similar viruses.

We report the demonstration of antimicrobial conjugated polyelectrolytes (CPEs) with high NIR absorbance for selective and efficient photothermal killing of bacteria over mammalian cells. The antimicrobial CPE possessing quaternary ammonium (QA) terminated side chains (P1) shows higher binding preference and increased dark toxicity towards Gram-positive and Gram-negative bacteria over mammalian cells. Bestowed by π-conjugated backbones, P1 exhibits a high molar absorptivity of 39.8 L g−1 cm−1 at 808 nm with an efficient photothermal conversion efficiency of 33 ± 1%. Upon 808 nm laser irradiation, P1 shows enhanced bactericidal effects, but not to mammalian cells. Although the anionic CPE counterpart with the same polymer backbone but sulfonate terminated side chains (P2) possesses a similar photothermal conversion ability, it exhibits much lower antibacterial effects due to its low binding affinity. This study thus reveals that bacteria–CPE electrostatic interactions play a major role in bacterial recognition, although hydrophobic interactions also contribute.

The use of π-conjugated polymers (CPs) in conductive hydrogels remains challenging due to the water-insoluble nature of most CPs. Conjugated polyelectrolytes (CPEs) are promising alternatives because they have tunable electronic properties and high water-solubility, but they are often difficult to synthesize and thus have not been widely adopted. Herein, we report the synthesis of an anionic poly(cyclopentadienylene vinylene) (aPCPV) from an insulating precursor under mild conditions and in high yield. Functionalized aPCPV is a highly water-soluble CPE that exhibits low cytotoxicity, and we found that doping hydrogels with aPCPV imparts conductivity. We also anticipate that this precursor synthetic strategy, due to its ease and high efficiency, will be widely used to create families of not-yet-explored π-conjugated vinylene polymers.

Photocatalytic hydrogen evolution is viewed as a promising green strategy to utilize the inexhaustible solar energy and provide clean hydrogen fuels with zero-emission characteristic. The nature of semiconductor-based photocatalysts is the key point to achieve efficient photocatalytic hydrogen evolution. Conjugated materials have been recently emerging as a novel class of photocatalysts for hydrogen evolution and photocatalytic reactions due to their electronic properties can be well controlled via tailor-made chemical structures. Hydrophilic conjugated materials, a subgroup of conjugated materials, possess multiple advantages for photocatalytic applications, thus spurring remarkable progress on both material realm and photocatalytic applications. This minireview aims to provide a brief review of the recent developments of hydrophilic conjugated polymers/small molecules for photocatalytic applications, and special concern on the rational molecular design and their impact on photocatalytic performance will be reviewed. Perspectives on the hydrophilic conjugated materials and challenges to their applications in the photocatalytic field are also presented.

International audience; Poly(thiophen-3-ylacetic acid) (PTAA) is a representative of conjugated polyelectrolytes which are used in many optoelectronics devices. The performance of these devices is affected by the polymer conformation, which, among others, depends on the nature of the counterion. In this study, the binding of tetrabutylammonium counterions (TBA +) on PTAA was determined using a combination of nuclear Overhauser effect spectroscopy (NOESY) and molecular dynamics (MD) simulation. It was found that TBA + ions specifically bind on the hydrophobic main chain of PTAA, while, according to MD simulations, alkali counterions predominantly bind in the vicinity of negatively charged carboxylic groups located on side chains. The MD trajectories were used to compute the relaxation matrices and the NOESY spectra. With the help of these latter calculations, the changes of intensities in experimental NOESY spectra upon binding of TBA + ions to PTAA were interpreted.

Aqueous palladium-catalyzed direct arylation polymerization (DArP) of 2-bromothiophene derivatives 6-(2-(2-bromothiophen-3-yl)ethoxy)hexyl trimethylammonium bromide (T1) and 4-(2-(2-bromothien-3-yl)ethoxy)butylsulfonate (T2) is achieved. The supporting ligand, triphenylphosphine-3,3',3''-trisulfonic acid trisodium salt (m-TPPTs), facilitates DArP of both derivatives; however, its separation from the polymers by dialysis is difficult due to its strong aggregation in water and N,N-dimethylacetamide (DMAc). This is supported by dynamic light scattering, gel permeation chromatography (GPC), and single-crystal X-ray crystallography. Pyrimidine-Pd(OAc)2 is utilized in the DArP of T1 to afford PT1 without ligand contamination. Density functional theory calculations to determine the coordinating capability of the carboxylate/pivalic acid/water to palladium indicate the viability of implementing DArP in water. Finally, polyelectrolyte molecular-weight overestimation by GPC in water is attributed to the polyelectrolyte effect. Aggregation of the conjugated polyelectrolytes leads to a contracted hydrodynamic volume, and the molecular weight and dispersity assessed by GPC in DMAc significantly deviate from the actual values. An objective approach to evaluate the molecular weight for conjugated polyelectrolytes requires further development.

Conjugated polyelectrolytes and their precursors as electron-injection layer (EIL) in polymer light-emitting diode have attracted extensive attention because they allow the use of environmentally stable high work function metals as cathode with efficient electron injection. Here, for the first time, we find that an undesirable green emission component (470–650 nm) in the electroluminescence spectra is observed during continuous operation of deep-blue emission β-phase poly(9,9-dioctyl-2,7-fluorene) (β-PFO) device upon introducing polyelectrolyte poly[9,9-bis(6′-(18-crown-6)methoxy)hexyl fluorene] chelating to potassium ion (PFCn6:K+) as EIL. This phenomenon also happens to nonchelating PFCn6, poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)], or even nonemissive poly[4-((18-crown-6)methoxy)methyl styrene] chelating to K+ (PSCn6:K+). It can be ascribed to electric-field induction accompanied by thermal motion of a highly polar side chain in the polyelectrolyte leading ...

Organic light-emitting transistors (OLETs) show the fascinating combination of electrical switching characteristics and light generation capability. However, to ensure an effective device operation, an efficient injection of charges into the emissive layer is required. The introduction of solution-processed conjugated polyelectrolyte (CPE) films at the emissive layer/electrode interface represents a promising strategy to improve the electron injection process by dipole formation. However, their use in optoelectronic devices also involves some limitations because of the ionic nature of CPEs. In this context, neutral conjugated polar polymers (CPPs) represent a valid alternative to CPEs because the conjugated backbones of CPPs are functionalized with polar nonionic side groups, thus avoiding ion-dependent drawbacks. By introducing a layer of polyfluorene-containing phosphonate groups underneath the metal electrodes, we here demonstrate a substantial improvement of the electron injection properties into the OLET-emissive layer and, accordingly, a more than 2-fold increased light power and a 5 times higher external quantum efficiency of p-type OLETs in comparison with reference devices without any interlayer. The great benefit of using a transparent glass substrate allowed to selectively investigate the morphological and photoluminescent characteristics of both CPE- and CPP-buried interlayers within complete OLETs by means of an optical scanning probe technique. This, together with a thorough optoelectronic characterization of the figures of merit of working light-emitting devices, allowed to disclose the origin of the improved optical performance of CPP-based devices as well as the operation mechanisms of the investigated interlayer in the corresponding OLETs.

Three conjugated polyelectrolytes(CPEs) based on thiophene, thieno[3,2-b]thiophene, and 2,2'-bithiophene were designed and synthesized. The CPEs were successfully incorporated into polymer solar cells as pH-neutral hole-transporting layer(HTL) via solution process. The interfacial dipole and work function(WF) of CPE-coated ITO were controlled by the dipole moment of the polymer, which was in turn determined by the stereochemical properties of the molecular structure. CPE-coated ITOs showed sequentially stronger dipole moments due to an increase in the electrostatic repulsion in the molecules. The PCE of device with PFT as the HTL was maintained accompanied by 16% decrease when PEDOT:PSS-based device decreased over 50%.

We have previously reported the formation of complexes between oppositely charged, conjugated polyelectrolytes (CPECs), resulting in electronic energy transfer between the donor and acceptor components. The ionic self-assembly process that forms CPECs is heavily influenced by environmental circumstances including solvent composition, temperature, and pH. In this article, we report the effect of polyelectrolyte chain protonation on complex formation and resulting energy transfer. The particular polyelectrolytes used in this study were a pH inactive energy donor and an acceptor polymer with protonatable sidechains. We find that over a large range of acidic pH, the optical properties do not change appreciably up to precipitation (pH 3). Surprisingly in the basic regime where the acceptor polymer is fully deprotonated, complex formation is hindered. However, at pH 11, which corresponds to an excess ion concentration of 0.001 M, the photophysical properties of the complex begin to once again resemble that of the neutral or acidic environments. Our results show that the CPEC displays impressive stability over a relatively broad range of proton concentrations, which may have implications for the construction of supramolecular light-harvesting assemblies.

Conjugated polyelectrolytes (CPEs) have been applied as sensors for various small molecules and ions including biologically important ions. Here we report the synthesis of two different polyphenylene ethynylene (PPE) type cationic CPEs and studied their biologically important phosphate ion sensing properties. These CPEs are substituted with branched polyammonium units; polymer P-O-3 features an –O–CH2– linker between phenylene units and the cationic side chains, whereas P-C-3 has an –CH2– linker. The different linkers lead to a difference in intrinsic tendency of the CPEs to aggregate in water. We report amplified fluorescence quenching, Stern–Volmer constants (Ksv), fluorescence correlation spectroscopy, and different anion sensor response of the polymers. The investigation of these two CPEs for anion sensing reveals that they are considerably more sensitive to di-phosphonates than to di-carboxylates or di-sulfonates. Fluorescence quenching is a result of polymer aggregate formation due to electrostatic interactions and hydrogen-bonding between dianions and the cationic CPEs. Polymer P-C-3, which has lower tendency to aggregate in water, was found to be a more efficient sensor than P-O-3 for PPi and ATP. Stern–Volmer quenching constants (Ksv) of P-C-3 by PPi and ATP are greater than 105 M−1. Furthermore, a real-time fluorescence assay for ALP-catalyzed hydrolysis of pyrophosphate (PPi) is demonstrated.

Conjugated polyelectrolytes (CPEs) are characterized by an electronically delocalized backbone bearing ionic functionalities. These features lead to properties relevant for use in energy-storing pseudocapacitor devices, including ionic conductivity, water processability, gel-formation, and formation of polaronic species stabilized by electrostatic interactions. In this Perspective, the basis for evaluating the figures of merit for pseudocapacitors is provided, together with the techniques used for their evaluation. The general utility and challenges encountered with neutral conjugated polymers are then discussed. Finally, recent advances on the use of CPEs in pseudocapacitor devices are reviewed. The article is concluded by discussing how their miscibility in aqueous media permits the incorporation of CPEs in living materials that are capable of switching function from extraction of energy from bacterial metabolic pathways to pseudocapacitor energy storage.

Owing to its high wettability and the resulting compatibility with the future industrial device fabrication process, the conjugated polyelectrolyte (CPE) has becoming a promising hole-transporting material (HTM) in the inverted perovskite solar cell (iPSC); however, only a few highly efficient CPEs have been reported probably due to the limited pool of molecular designing strategies. Here we construct a CPE named DTB(Na) with the same main-chain of a polymer DTB(EH) that was previously employed as a dopant-free HTM in a highly efficient regular type PSC (rPSC) and with simple water/alcohol soluble side-chains. Compared with its analog bearing the only variation of less thiophene units in the main-chain, DTB(Na) shows stronger capacities of hole-extraction and defect-passivation, which should be ascribed to the more intensive exposure of thiophene functional unit to the perovskite layer. As a result, the DTB(Na) iPSC device presents enhanced values on all the photovoltaic parameters and long-term stability, and a power conversion efficiency of 19.92% is realized. Our results demonstrate the feasibility for efficient polymeric HTMs in rPSCs and iPSCs to share the same main-chains, thus enriching the molecular designing strategies and probably expanding the library of efficient HTMs for iPSCs.

The incorporation of conjugated polyelectrolytes as cathode interlayers in organic photovoltaics has been proven to be an effective way to boost the device efficiency. Nevertheless, more detailed investigations of the structure property relationships of these interlayer materials, in particular related to the film deposition behavior, can provide further insights into their mode of action. With this aim, a series of ionic (co)polythiophenes is successfully synthesized via Kumada catalyst-transfer condensation polymerization and subsequent introduction of ionic moieties on the polymer side chains. Both the topology (i.e. homopolymers, random and block copolymers) and the amount of ionic groups are systematically varied. The polymers are fully characterized and then applied as cathode interlayers in polymer solar cells based on PCDTBT:PC71BM, affording an average efficiency increase of similar to 15%. The structural screening on one hand indicates that the efficiency gain is a rather general phenomenon for this material class. On the other hand, the best photovoltaic responses are observed for the conjugated polyelectrolytes with a higher triethylene glycol side chain ratio and the block copolymer structure performs slightly better as compared to the random copolymer with the same (50/50) monomer ratio. Based on these findings, the field can move on to a more rational development of novel interfacial materials and thereby push the device efficiency even further. This work was supported by the Research Foundation-Flanders (FWO) (project G.0415.14N and postdoctoral fellowship J.K.). S.G. acknowledges Hasselt University for her (BOF) doctoral grant. TA Instruments is acknowledged for the RHC equipment.

Suzuki coupling and Ni-catalyzed Yamamoto polymerizations were used to prepare conjugated polyelectrolytes based on n-type benzothiadiazole and benzotriazole unit backbone via a one-step synthesis, which started from their monomers with charged pendant ends. PBTBTz-SO3Na synthesized by Suzuki coupling polymerization showed a high M n value of 94 kDa, starting from the bilateral brominated benzotriazole and diboronic ester benzothiadiazole. The PBTBTz-SO3Na revealed aggregation phenomenon at the status of diluted solutions at optical absorption spectroscopy results. Dynamic light scattering (DLS) measurement provided evidence of negative solvatochromic effects of PBTBTz-SO3Na chains in solvents with lower polarity. While, PBTz-PyrBr, PBTz-TMABr, and PBTz-SO3Na which synthesized from Ni-catalyzed Yamamoto polymerizations of bilateral brominated benzotriazole units revealed higher molecular weight with PBTz-PyrBr, M n = 112 kDa; PBTz-TMABr, M n = 157 kDa; and PBTz-SO3Na, M n = 172 kDa, respectively. The ionic pendant groups of monomers have influence on the molecular weight of polymer based on benzotriazole backbone. The optical absorption spectroscopy and DLS measurements presented the negative solvatochromic effects of cationic-CPEs, PBTz-PyrBr, and PBTz-TMABr. Moreover, the UV-vis absorption of PBTz-TMABr displayed higher wavelength of solution (0.0167 mg/mL) than that of film, which was coated from its solution with concentration of 5 mg/mL. These studies displayed insights into the role of pendant ionic functionalities on the molecular weight and optoelectronic properties of the CPEs, which may find application in optoelectronic devices.

Conjugated polymer nanoparticles (CPNs) possess many useful and fascinating properties, including high brightness, excellent photostability, good water-dispersibility, low cytotoxicity, and easy functionalization, showing promising application in bioimaging. In this work, one kind of optical/magnetic conjugated polyelectrolyte has been designed and synthesized by introducing Mn(III) porphyrin (T1-weighted relaxivity) into a fluorescent fluorene based polymer backbone. Fluorescent/magnetic conjugated polymer nanoparticles (FM-CPNs) were prepared by self-assembly in the phosphate buffer solution caused by their amphiphilic structures with hydrophobic backbones and hydrophilic side chains. Their photophysical properties have been investigated in details via UV–vis absorption and fluorescent emission spectra. Investigation of its magnetic properties has shown that the FM-CPNs exhibit high T1-weighted relaxivity value, making them promising candidates for T1-enhanced magnetic resonance imaging agent. Further cell imaging has been realized successfully using FM-CPNs as staining label, and cytotoxicity was evaluated by the methyl thiazolyl tetrazolium (MTT) assay.

Narrow band-gap conjugated polyelectrolytes (NBGCPs) combine the advantages of narrow band-gap conjugated polymers and polyelectrolytes. However, they are limited reported and seldom used in polymer solar cells (PSCs). Herein, we design and synthesized two PTB7-based NBGCPs, cationic PTB7-NBr and zwitterionic PTB7-NSO 3 , as cathode interlayers (CILs) in conventional PSCs. Compared to poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2- b :4,5- b′ ]dithiophene-2,6-diyl- alt -ethylhexyl-3-fuorothithieno[3,4- b ]thiophene-2-carboxylate-4,6-diyl] (PTB7), both PTB7-NBr and PTB7-NSO 3 have similar absorption while PTB7-NBr has a higher HOMO level than PTB7 and PTB7-NSO 3 . With PTB7-NBr and PTB7-NSO 3 as CIL and Al as cathode, the devices both exhibited high efficiencies. The optimal power conversion efficiencies (PCEs) of PTB7-NBr device and PTB7-NSO 3 device are about 9%. However, PTB7-NBr devices are less sensitive to the CIL film thicknesses and the PCEs of PTB7-NSO 3 device decrease sharply when the thickness of PTB7-NSO 3 over 3 nm. What's more, when the devices with an Ag cathode PTB7-NBr exhibits a much better interfacial modification than PTB7-NSO 3 . Ultraviolet photoelectron spectroscopy (UPS) indicate that the work functions of PTB7-NBr and PTB7-NSO 3 film on Al are identical while on Ag they are different. We suggest the insensitivity to CIL thickness and good performance for Ag device of PTB7-NBr devices are attributed to the bromide anions in PTB7-NBr. The report on PTB7-based NBGCPs broads the types of organic cathode interfacial materials and is beneficial to the deep insight of ionic effect in electrolyte materials.

In the past two decades, bulk heterojunction-organic photovoltaic devices (BHJ-OPVs) have emerged as attractive candidates for solar energy conversion due to their light-weight design and potential for low-cost high-throughput, solution-phase processability. Interfacial engineering is a proven efficient approach to achieve OPVs with high power conversion efficiencies (PCEs). This mini-review provides an overview of the key structural considerations necessary when undertaking the molecular design of conjugated polyelectrolytes (CPEs), for application as interfacial layers (ILs). The different roles of ILs are outlined, together with the advantages and disadvantages of competing classes of IL materials. Particular emphasis is placed on the design and synthesis of water-soluble polythiophene-based IL materials and the influence of their structural characteristics on their performance as a promising class of IL materials. Finally, the challenges and opportunities for polythiophenes as IL materials for OPVs and other solution-processed solar cell technologies (e.g. perovskite solar cells) are discussed.

An organic soluble precursor polymer was prepared by direct (hetero)arylation polymerization of 3,4-ethylenedioxythiophene (EDOT) with a solubilizing, 3,4-propylenedioxythiophene (ProDOT) derivative bearing ester-functionalized side chains. Chemical defunctionalization of the polymer, using base to hydrolyze the esters, yields a conjugated polyelectrolyte (CPE) that is readily soluble in water. This aqueous soluble CPE can then be processed using high-throughput coating methods from water-based inks. Postprocessing functionalization of the polymer film using dilute acid creates a solvent resistant film that is compatible with both organic and aqueous electrolyte systems for redox switching. The introduction of an unfunctionalized EDOT unit results in a soluble polymer that has a low oxidation potential and that is highly electroactive and pseudocapacitive in a wide voltage range (2 V in propylene carbonate-based electrolytes and 1.55 V in aqueous electrolytes) making it an attractive material for lightwei...

A novel n-type cationic conjugated polymer (PFSOmiCl), consisting of bispyrimidinium-dibenzothiophene-S,S-dioxide and fluorene scaffolds, was developed from its polymeric precursor (PFSOmi) through an intramolecular cyclization reaction. In comparison with PFSOmi, PFSOmiCl exhibits significant bathochromical absorption and photoluminescence spectra in both solution and film form, as well as a more hydrophilic film surface. Cyclic voltammetry tests demonstrate that PFSOmiCl possesses a deep lowest unoccupied molecular orbital (LUMO) energy level of −4.18 eV, which is comparable to the LUMO energy levels of common fullerene derivatives. These unique properties endow PFSOmiCl with great utilization potential in organic optoelectronic devices. Moreover, this research offers a novel guideline for designing new conjugated polyelectrolytes.

A series of novel conjugated polyelectrolytes composed of two different building blocks with different composition ratios were designed and synthesized for application as a functional layer in high-performance organic photodiodes (OPDs). A homopolymer and two random copolymers were prepared using different molar ratios of dibromo 1,4-bis(4-sulfonatobutoxy)benzene (SPh) and dibromo 1,4-bis(4-tetraethylene glycol)benzene (EGPh): EG20 with SPh:EGPh ratio of 0.8:0.2 and EG40 with a ratio of 0.6:0.4. Structural analyses by two-dimensional grazing-incidence X-ray diffraction and near-edge X-ray absorption fine structure spectroscopy studies proved that a higher EGPh content could induce more organized polymer chains with face-on orientation of EG20 and EG40. Such an orientation of EG20 and EG40 along with the ordered crystalline organization yielded effective molecular dipole moments in the thin films when applied as an interlayer between ZnO and an active layer of inverted OPDs. As confirmed by ultraviolet pho...

Synthesis of fluorene-based conjugated polyelectrolytes was achieved via Suzuki polycondensation in water and completely open to air. The polyelectrolytes were conveniently purified by dialysis and analysis of the materials showed properties expected for fluorene-based conjugated polyelectrolytes. The materials were then employed in solar cell devices as an interlayer in conjunction with ZnO. The double interlayer led to enhanced power conversion efficiency of 10.75 % and 15.1 % for polymer and perovskite solar cells, respectively.

A series of new conjugated polyelectrolytes (CPEs) containing tetraphenylethene units are synthesized and characterized. They show apparent aggregation-induced emission (AIE) characteristics and give fluorescence covering from cyan to red with high emission efficiencies in aggregates. These AIE CPEs can directly enter and stain living cells for fluorescence imaging with low cytotoxicity, and can provide information on cellular viscosity at different locations based on fluorescence lifetime imaging.

In this paper, a novel homogeneous hybridization chain reaction (HCR) assay is developed by using cationic conjugated polyelectrolytes (CPEs) as an indicator for the detection of DNA. In this assay, two hairpin probes H1 and H2 are labeled with fluorescein at their 5′-end and 3′-end respectively. After the HCR, the two hairpin probes are triggered by target DNA to form a long two-stranded DNA polymer with numerous fluorescein labelling in the strand, which is resistant to the S1 nuclease degradation. When the CPEs are added, strong electrostatic interaction between fluorescein-labeled DNA and CPEs occurred, which allowed fluorescence resonance energy transfer (FRET) from the CPEs to the fluorescein-labeled DNA and an obvious fluorescence colour change of the conjugated polymer solution. With HCR amplification and CPEs to amplify the fluorescence signal, homogeneous HCR for sensitive DNA detection is performed successfully. This proposed cascade amplification strategy can not only extend the application of HCR but also provides an alternative platform for homogeneous detection of DNA.

Self-compensated (SC) hole-doped conjugated polyelectrolytes with high work functions can provide efficient hole-injection and -collection layers for organic and other semiconductor devices. If these films can be photocrosslinked, the semiconductor overlayer can be deposited from a wider range of solvents, enabling flexibility in device design and fabrication. However, a generic photocrosslinking methodology for these materials is not yet available. Here, we demonstrate that sFPA82-TfO, the recently developed bis(fluorophenyl azide) photocrosslinker that is also i-line compatible, can surprisingly give 100% efficient photocrosslinking for SC hole-doped conjugated polyelectrolytes, i.e., one crosslink per reactive moiety, using mTFF-C2F5SIS-Na, a triarylamine–fluorene copolymer, as the model polyelectrolyte, without degrading its ultrahigh work function of 5.75 eV. The photocrosslinking efficiency is much higher than in the corresponding undoped polyelectrolyte and nonconjugated polyelectrolyte films, wher...

Photon pressure has been used to induce the aggregation from solution of a series of photoluminescent conjugated polyelectrolytes containing tetraphenylethene units. These polymers show steady-state and time-resolved emission properties that are dependent on the local chromophore environment that can be influenced by the degree of intra- and inter-molecular interactions, which enables the photoaggregation process to be monitored by time-resolved fluorescence imaging techniques. Structural differences in the polymer lead to variations in the photo-induced aggregation behaviour.

Organic-inorganic hybrid light-emitting diodes (HyLEDs) consist of an organic emission layer in combination with at least one metal oxide charge injection layer, typically in an inverted structure. Low temperature, solution processing of metal oxide charge injection layers is one of the key factors in reducing the manufacture cost of HyLEDs. Herein, we report the use of composite materials, comprising conjugated polyelectrolytes (CPE) and zinc oxide nanoparticles (ZnO NPs), as the electron injection layer (EIL) in highly-efficient, green-light-emitting poly (9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) polymer LEDs that are carefully optimised for use in an inverted HyLED architecture for the first time. The composite CPE:ZnO EILs are processed via a room temperature, one-step, solution deposition and enable superior device performance relative to ZnO NPs on their own. We find that specifically, they (i) improve EIL morphology, reducing surface roughness as well as pin-hole size and density, (ii) induce a favourable vacuum level shift for electron injection by coordinate bonding between the CPE and ZnO constituents, and (iii) reduce interfacial quenching by passivation of ZnO chemical defects caused by oxygen vacancies. This work is also the first demonstration that blending ZnO NPs and CPE supports much faster electroluminescence turn-on times (~7.12 μs) than for traditional ZnO/CPE bilayer devices (~0.4 s) via ‘locking’ of the CPE mobile ions, as well as higher device performance. This demonstrates good suitability for display applications. After optimisation of the EIL composition and the thickness of the F8BT emissive layer, we achieve promising device efficiencies of 16.5 cd/A and 5.4 lm/W for devices with a 1.1 μm thick F8BT layer, which is particularly relevant for potential roll-to-roll fabrication. These results clearly demonstrate the potential that this organic-inorganic composite EIL material has for the realisation of cheap, scalable and highly efficient, printable HyLED devices.

Ionic polythiophenes are important conjugated polymers because of their excellent optical properties and water solubility. They are classified as cationic, anionic and zwitterionic conjugated polyelectrolytes. This review article describes concisely their biological and analytical applications. The specific detection of different negatively charged biomolecules such as DNA and adenosine triphosphate, anions like halides and toxic pseudo-halide (CN−) and environmental pollutants, e.g. surfactants, is discussed. The conformational changes of cationic polythiophenes (CPTs) induced by various analytes due to formation of ionic conjugates and the cooperative responses of all segments cause dominant signal amplification even in the presence of a small perturbation. In addition, reactive oxygen scavenging, antimicrobial photosensitizing and cell imaging applications of CPTs are documented. Use of anionic polythiophenes for sensing of protamine and cations like Cu2+ and Ca2+ is also discussed. Finally, sensing of DNA, peptides and surfactants by zwitterionic polythiophenes is included. The concluding part discusses future prospects. © 2016 Society of Chemical Industry

The synthesis and photophysical properties of poly{3-[6-(triethylphosphonium)hexyl]-thiophene-2,5-diyl bromide} and poly{3-[6-(triphenylphosphonium)hexyl]-thiophene-2,5-diyl bromide} are reported in the present contribution. Three various polymer precursors (poly[3-(6-bromohexyl)thiophene-2,5-diyl]s) with molecular weights 7.2, 11.8 and 13.2 kg mol−1 respectively and head to tail regioregularity from 62% to 94% were prepared and consecutively transformed into the corresponding polyelectrolytes by a simple quaternization reaction with appropriate phosphines. Synthesized polyelectrolytes exhibited solvatochromism. Detailed aggregation experiments via changing water/DMSO ratio have been performed. Photoluminiscence spectra of the polyelectrolyte solutions indicate that the emission maxima are red-shifted gradually with the increasing solvent polarity. Fluorescence quenching has been studied by interaction with model quenchers: K4[Fe(CN)6] and K3[Fe(CN)6] in water using Stern-Volmer methodology.

The reaction of 2-ethynylpyridine (2EP) with stoichiometric equivalent of an alkyl halide RX (R is ethyl, nonyl, or hexadecyl and X is Br or I) gives a poly(N-alkyl-2-ethynylpyridinium halide) type ionic polymer that belongs to the family of π-conjugated polyelectrolytes (CPEs). Reaction conditions significantly influence configuration of the polymer main chains: polymerization in acetonitrile solution gives polymers with high content of cis units while bulk polymerization provides irregular cis/trans polymers. Increased regularity of the high-cis polymers is documented by the NMR and IR as well as SERS (surface enhanced Raman scattering) spectra measured on Ag-nanoparticles/CPE systems. Both polymerization processes give polymers in which 2EP monomeric units are ionized only from ca one half, which exhibit good stability in air and good solubility in polar solvents such as MeOH, DMF, and DMSO and those with N-ethylpyridinium groups even in water.

We report a self-referencing ratiometric nanothermometer based on short conjugated polyelectrolytes (CPEs). The probe is prepared by complexing a phenylene-based polymer with polyvinylpyrrolidone (PVP), an amphiphilic macromolecule that destabilizes CPE π–π stacking. This makes it possible to shift the equilibrium between the less emissive aggregated state of the CPE (520 nm) and its more emissive single chains (450 nm) within a useful temperature range (15.0–70.0 °C). By testing different PVP molecular weights, we managed to tune the probe thermal sensitivity and response time. Given its potential wide applications, the probe was tested under different pHs and using divalent and monovalent cations. We believe the reported nanothermometer will prove instrumental for ongoing efforts to accurately map and investigate heat production and dissipation at the nanoscale level.

Systematic investigation of the instinctive self-assembly of diblock conjugated polyelectrolytes (CPEs) as electron transport layers (ETLs) on the arrangement and morphology of the upper active layer in polymer solar cells (PSCs) is usually ignored. The two water/alcohol-soluble diblock CPEs with different terminal ionic groups, PFEO-b-PTNBr and PFEO-b-PTImBr, offer an ohmic contact between the ITO electrode and the active layer by substantially reducing the work function of ITO via modulation of the interfacial dipoles. More intriguingly, the spontaneous self-assembly of the diblock polymers causes an ordered scolopendra-like conformation to develop on the ITO cathode. These self-assembled diblock CPEs can act as a template to further partially induce a preferable face-on orientation of the donor component. Surprisingly, n-type self-doping is observed in the two CPEs based on the p-type conjugated backbone, particularly in PFEO-b-PTImBr with imidazolium salt. As a result, the power conversion efficiencies (PCEs) of the devices based on PTB7-Th:PC71BM are remarkably enhanced to 9.0% for PFEO-b-PTNBr and 9.4% for PFEO-b-PTImBr. Intriguingly, both ZnO/PFEO-b-PTNBr and ZnO/PFEO-b-PTImBr based PTB7-Th:PC71BM devices exhibit superior PCEs compared to that of the classical published and commonly used PFN (8.42%) and PFNBr (8.38%) ETLs based devices. These results indicate that the development of self-assembled diblock CPEs opens a new point of view and provides a straightforward approach to achieve high performance polymer solar cells by simultaneously modulating the morphology of the interlayer, active layer and interfacial work function.

A series of neutral conjugated polymers (NCPs) and conjugated polyelectrolytes (CPEs) containing tetraphenylethene (TPE) were synthesized and characterized. Due to the presence of TPE units, NCPs exhibit aggregation-induced emission characteristics and strong fluorescence in the aggregated state. NCPs can function as fluorescent probes to detect 2,4,6-trinitrophenol in aqueous media with extremely high sensitivity, low detection limit and good anti-photobleaching properties. The value of quenching constants (Ksv) is by up to 1.72 × 107 M−1 and the detection limit is as low as 5 nM. NCPs can also be made into the fluorescence test strips for the detection of 2,4,6-trinitrophenol in a practical application. The corresponding CPEs are obtained from the facile reaction of the NCPs with pyridines. The CPEs exhibit low cytotoxicity and can be used to track lysosomes in HeLa cells, which is meaningful in visualizing and understanding intracellular metabolism and various physiological processes. Based on the identical polymer skeleton, these conjugated polymers could be employed as fluorescent probes for multipurpose application.

Thermal sensing in thin films polymers has been a significant limitation towards optimizing the heat dissipation in micro- and nano-electronic devices as well as many other thin film-based technologies. In this work, we report on poly (phenylene ethynylene) fluorescent-based conjugated polyelectrolyte capable of detecting thermal fluctuations in polymer films prepared from polyvinylpyrrolidone-co-vinyl acetate. The sensor was first optimized in solution by testing two polyvinylpyrrolidone (PVP) copolymers (co-vinyl acetate (VA) and co-polystyrene (PS)) before it was spun cast onto quartz slides and imaged using a DSLR camera at different temperatures. The images were analyzed and showed a change in color with the increase in temperature. When not illuminated, the polymer thin film is clear and transparent.

We describe a new trypsin assay on the basis of changes in fluorescence color (red-to-blue) of a hollow microcapsule. The microcapsule assay was designed based on the manipulation of intermolecular exciton migration of a conjugated polyelectrolyte in the microcapsule as follows. (1) The red-emitting, hollow microcapsule was fabricated via electrostatic self-assembly using conjugated polyelectrolytes (polyanion) and polyarginine (polycation). (2) One of the building blocks of the microcapsule, polyarginine, could be hydrolyzed by the enzymatic action of trypsin. (3) The hydrolysis resulted in destruction of the microcapsule, leading to the release of the red-emitting, conjugated polyelectrolytes into an aqueous phase. (4) Gradually, the conjugated polymer became soluble and the red-emissive color of the conjugated polyelectrolytes turned to blue, because of dominant intramolecular exciton migration in the aqueous solution. As such, trypsin could be easily sensed by the naked eye-detectable emission color change. This emission color-changeable sensing protocol can be applied to other protease assays simply by changing the corresponding polypeptide.

Alkoxy side-chain tethered polyfluorene conjugated polyelectrolyte (CPE), poly[(9,9-bis((8-(3-methyl-1-imidazolium)octyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-methoxyethoxy)ethyl)-fluorene)] dibromide (F8imFO4), is utilized to obtain CPE-hybridized ZnO nanoparticles (NPs) (CPE:ZnO hybrid NPs). The surface defects of ZnO NPs are passivated through coordination interactions with the oxygen atoms of alkoxy side-chains and the bromide anions of ionic pendent groups from F8imFO4 to the oxygen vacancies of ZnO NPs, and thereby the fluorescence quenching at the interface of yellow-emitting poly(p-phenylene vinylene)/CPE:ZnO hybrid NPs is significantly reduced at the CPE concentration of 4.5 wt%. Yellow-emitting polymer light-emitting diodes (PLEDs) with CPE(4.5 wt%):ZnO hybrid NPs as a cathode interfacial layer show the highest device efficiencies of 11.7 cd A−1 at 5.2 V and 8.6 lm W−1 at 3.8 V compared to the ZnO NP only (4.8 cd A−1 at 7 V and 2.2 lm W−1 at 6.6 V) or CPE only (7.3 cd A−1 at 5.2 V and 4.9 lm W−1 at 4.2 V) devices. The results suggest here that the CPE:ZnO hybrid NPs has a great potential to improve the device performance of organic electronics.

An optical nanoruler system based on a conjugated polyelectrolyte-silver nanoprism pair is developed for label-free protein detection by taking advantage of the metal-enhanced fluorescence effect of silver nanostructures. Antibody-antigen interactions induce a change in the metal-fluorophore distance, followed by the response of a fluorescent signal of the conjugated polyelectrolyte. The system is used to detect target antigens sensitively and selectively.