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In the realm of flexible optoelectronic devices, intrinsic flexible fully π‐conjugated polymers (FπCPs) assume a pivotal role owing to their concurrent intrinsic viscoelasticity and robust optoelectronic properties. As flexible devices are destined to encounter diverse stress environments, the selection of functional materials based on mechanical requirements becomes imperative. Here, VPERD assessment system is introduced to scrutinize the mechanical properties of side‐chain plasticizing FπCPs. The acronym VPERD encapsulates five key aspects of mechanical characteristics, namely viscidity (V), plasticity (P), elasticity (E), rigidity (R), and ductility (D). The mechanical characteristics of FπCPs are tuned through the control of flexible chain density (FCD). Enhancing FCD induces superior chain softness, favorable solubility, and heightened viscoplasticity. Through precise regulation of FCD and thoughtful structural design, freestanding FπCPs nano‐films exhibit a remarkable maximum fracture strain of ≈50%. Deep‐blue flexible polymer light‐emitting diodes (PLEDs) reveal that maintaining FCD at ≈50% achieves a balance between mechanical and optoelectronic properties. The stretched films after strain fatigue both show that mild strain is conducive to enhancing the efficiency of FπCPs films and devices. According to VPERD assessment system, the prerequisite for achieving intrinsically flexible FπCPs lies in controlling the degree of side‐chain internal plasticization through the tuning of FCD. [ABSTRACT FROM AUTHOR]

High‐performing n‐type polymers are crucial for the advance of organic electronics field, however strong electron‐deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide‐functionalized polycyclic aromatic hydrocarbons (PAHs) with extended π‐conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high‐performance n‐type polymers. Among the PAHs, phenanthrene (PhA) features a well‐delocalized aromatic π‐system with multiple modifiable active sites. However, the PhA‐based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhAs, CPOI and CPCNI, by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA. Notably, the dicyanomethylene‐modified CPCNI exhibits a well stabilized LUMO energy level (−3.84 eV), attributed to the synergetic inductive effect from imide and cyano groups. Subsequently, based on CPOI and CPCNI, two polymers PCPOI‐Tz and PCPCNI‐Tz were developed. Applied to organic thin‐film transistors, owing to the strong electron‐deficiency of CPCNI, polymer PCPCNI‐Tz shows an improved electron mobility and largely decreased threshold voltage compared with PCPOI‐Tz. This work affords two structurally novel electron‐deficient building blocks and highlights the effectiveness of dual functionalization of PhAs with strong electron‐withdrawing groups for devising n‐type polymers. [ABSTRACT FROM AUTHOR]

Conjugated polymers have attracted extensive attention in numerous research fields because of their exceptional photoelectric properties and distinctive solution processing capabilities. The conformation of the chain and the structure of the condensed state in solution are closely related to various factors, such as concentration and solvent. Concentration, as a significant external parameter, plays a crucial role in the self‐assembly and formation of crystalline structures in conjugated polymers. It also affects the properties of the solution, the structure of the membrane, and the performance of the fabricated devices. Recently, there have been an increasing number of studies conducted from the perspective of solution concentration. Therefore, it is important to comprehensively summarize the effect of concentration on the transition process of chain structure from solution to film, as well as the impact of concentration on the performance of related devices. In this review, we summarize the effects of concentration on the chain motion, particle size, ordered structure, and photoelectric properties of conjugated polymers in solutions and thin films, as well as on device efficiency. This provides a unique perspective on the fundamental characteristics of conjugated polymers, which can assist in the development and improvement of optoelectronic devices. [ABSTRACT FROM AUTHOR]

Conjugated polymers (CPs) are upcoming optical contrast agents in view of their unique optical properties and versatile synthetic chemistry. Biofunctionalization of these polymer-based nanoparticles enables molecular imaging of biological processes. In this work, we propose the concept of using a biofunctionalized CP for noninvasive photoacoustic (PA) molecular imaging of breast cancer. In particular, after verifying the PA activity of a CP nanoparticle (CP dots) in phantoms and the targeting efficacy of a folate-functionalized version of the same (folate-CP dots) in vitro, we systemically administered the probe into a folate receptor-positive (FR+ve) MCF-7 breast cancer xenograft model to demonstrate the possible application of folate-CP dots for imaging FR+ve breast cancers in comparison to CP dots with no folate moieties. We observed a strong PA signal at the tumor site of folate-CP dots-administered mice as early as 1 hour after administration as a result of the active targeting of the folate-CP dots to the FR+ve tumor cells but a weak PA signal at the tumor site of CP-dots-administered mice as a result of the passive accumulation of the probe by enhanced permeability and retention effect. We also observed that folate-CP dots produced ~4-fold enhancement in the PA signal in the tumor, when compared to CP dots. These observations demonstrate the great potential of this active-targeting CP to be used as a contrast agent for molecular PA diagnostic imaging in various biomedical applications.

Developing high‐performance but low‐cost n‐type polymers remains a significant challenge in the commercialization of organic field‐effect transistors (OFETs). To achieve this objective, it is essential to design the key electron‐deficient units with simple structures and facile preparation processes, which can facilitate the production of low‐cost n‐type polymers. Herein, by sequentially introducing fluorine and cyano functionalities onto trans‐1,3‐butadiene, we developed a series of structurally simple but highly electron‐deficient building blocks, namely 1,4‐dicyano‐butadiene (CNDE), 3‐fluoro‐1,4‐dicyano‐butadiene (CNFDE), and 2,3‐difluoro‐1,4‐dicyano‐butadiene (CNDFDE), featuring a highly coplanar backbone and deep‐positioned lowest unoccupied molecular orbital (LUMO) energy levels (−3.03–4.33 eV), which render them highly attractive for developing n‐type semiconducting polymers. Notably, all these electron‐deficient units can be easily accessed by a two‐step high‐yield synthetic procedure from low‐cost raw materials, thus rendering them highly promising candidates for commercial applications. Upon polymerization with diketopyrrolopyrrole (DPP), three copolymers were developed that demonstrated unipolar n‐type transport characteristics in OFETs with the highest electron mobility of >1 cm2 V−1 s−1. Hence, CNDE, CNFDE, and CNDFDE represent a class of novel, simple, and efficient electron‐deficient units for constructing low‐cost n‐type polymers, thereby providing valuable insight for OFET applications. [ABSTRACT FROM AUTHOR]

Green‐processable printed large‐area light‐emitting diode (LED) is the crucial component of the high quality solid lighting and flat‐panel display. Accelerating the replacement from fossil‐based solvents to sustainable ecofriendly solvent is desirable for solution‐based printed organic electronics. Herein, by simple introducing methyl to the benzene groups of polydiarylfluorene‐based polymer, this work realizes the solution processing of blue polymer light‐emitting diodes (PLEDs) with a bio‐based solvent of limonene toward large‐area printed display. Film processed from this solvent exhibits satisfactory morphology and remarkable photophysical performances, even though the polymer chains show more serious aggregation in solution. What's more, devices fabricated with spin‐coated films present higher external quantum efficiency (EQE) and better spectra repeatability. Encouraged by the good film‐forming ability of this polymer in limonene, this work realizes the fabrication of printed large‐area films (5 × 5 cm2) with uniform emission and surface morphology by blade coating. Furthermore, this work develops passive matrix (PM) PLEDs arrays with 20 × 20 pixels that can dynamically display monochrome letters and numbers, demonstrating the potential application of cost‐effective printing techniques in large‐area display. [ABSTRACT FROM AUTHOR]

Control of the secondary conformational behavior of light‐emitting conjugated polymers (LCPs) is essential to obtain deep‐blue emission with a narrowband and stable color purity. Naturally π–π interactions induced by the planar aromatic segments may be easily observed in liner‐type LCPs, which lead to reduced emission efficiency, color purity, and energy bandgap. Herein, an alternating copolymerization strategy is proposed to obtain the singlet exciton behavior of a planar conformational segment from polydiarylfluorenes‐copolymers (P7‐6DPF, P7‐8DPF, and P7‐9DPF) toward deep‐blue polymer light‐emitting diodes (PLEDs). Compared to the highly crystalline capacity of P7DPF, P7‐8DPF, and P8DPF, alternative P7‐6DPF and P7‐9DPF present a feature and well‐resolved emission from a planar conformational segment of polyfluorene without obvious polaron features and charge transfer states. More interestingly, P7‐6DPF and P7‐9DPF show thickness‐independent electroluminescence (EL) behavior with a stable deep‐blue color purity, which is the precondition to fabricate large‐scale and high‐quality PLEDs. Finally, compared to control devices, PLEDs based on the P7‐6DPF and P7‐9DPF planar (β) conformational films present a well‐resolved and narrowband emission, stable EL spectra, high brightness (two‐ to threefold), and high current efficiency (1.3‐fold). Therefore, optimizing hierarchical structure via alternating copolymerization is an effective strategy to improve the performance and stability of deep‐blue PLEDs. [ABSTRACT FROM AUTHOR]

Electron‐deficient ladder‐type π‐conjugated systems are highly desired for constructing polymer acceptors due to their unique electronic properties. Herein, two series of polymer acceptors PBTIn‐(F)T (n = 1–4) based on imide‐functionalized ladder‐type heteroarenes (BTIn) with tunable conjugation length are synthesized. Effects of their backbone configuration and electronic properties on film morphology and performance of all‐polymer solar cells (all‐PSCs) are systematically investigated through theoretical computation, Raman spectroscopy, grazing incidence wide‐angle X‐ray scattering, etc. It is found that the ladder‐type heteroarene size extension and polymer backbone fluorination gradually lower the frontier molecular orbital energy levels, leading to progressive bandgap narrowing with more efficient exciton dissociation. Furthermore, the centrosymmetric and axisymmetric characteristics of BTIn result in distinct backbone configuration with varied self‐aggregation and crystalline phases, hence determining the blend film morphology. The highest efficiencies in these two series are attained from PBTI3‐T and PBTI3‐FT with a curved backbone configuration. PBTI4‐(F)T with further extended heteroarenes shows linear backbone, negatively affecting film morphology and efficiency. This study provides fundamental material structure‐device performance correlations for ladder‐type heteroarenes‐based polymer acceptors for the first time and demonstrates that more extended ladder‐type backbones do not necessarily improve the device performance, offering guidelines for designing polymer acceptors to maximize all‐PSC performance. [ABSTRACT FROM AUTHOR]

The solventnatures are crucial to deeply reveal solution behavior of macromolecular chains, physical essence of condensed state structures formation of the film as well as the photoelectronic devices performance. Based on the second virial coefficient (A2), effect of the synergistic action of solvents and external electric field on both solution behavior and the film's condensed state structure for the semi-rigid conjugated polymer, poly[2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylvinylene] (MEH-PPV) was investigated by dynamic/static light scattering, photoluminescence spectroscopy and transmission electron microscopy, etc. It was found that although the MEH-PPV solutions with different solvents (toluene, chlorobenzene, chloroform and tetrahydrofuran) all could generate a response to the external electric field, the degree of response varied significantly with the change of solvent nature. Furthermore, ordered degree of the film from the solutions was also obviously different. The essential reason for this responsive difference was firstly revealed in the research, which actually depended on the degree of interaction between the solute and solvent, and this degree of interaction could be quantitatively described by the second virial coefficient (A2). The bigger the A2, the stronger the interaction between solvent and solute in the solution, and the stronger the response to the external electric field. Further, under the induction of external electric field, chains aggregations with different sizes were formed accompanied by large-scale chains ordered structure in the solution. This ordered structure not only can effectively transfer to film prepared by the precursor solution but also is beneficial to enhance the carrier mobility and device efficiency of the photoelectronic film. [ABSTRACT FROM AUTHOR]

Solvents have an essential association with polymer solution behavior. However, few researches have been deeply done on this respect. In recent years, our research group focus on the study on effect of solvent properties on solution behavior and film condensed state structure for semi-rigid conjugated polymer up till to apply for optoelectronic device. Herein, influence of solvent properties including solubility of solvent, aromaticity, polarity and hydrogen bonds on semi-rigid polymer chain solution behavior, i.e., single chain conformation, chain shape, size and chains aggregated density were studied by means of static/dynamic laser light scattering (DLS/SLS) and exponential law etc. Effect of solvent properties on condensed state structure of the semi-rigid conjugated polymer film was studied by UV absorption spectroscopy, PL spectroscopy and electron microscopy etc. The essential reasons for the influence were discovered and the mechanism was revealed. It was found that solution behavior with different solvent properties had an essential physical relationship with chains condensed state structure of the semi-rigid conjugated polymers. More importantly, there was a quantitative structure-activity relationship between solution and film. The key to this relationship depended on the interaction between solvent molecules and the semi-rigid conjugated polymer chains. This interaction could also affect optoelectronic devices performance. This study is of great significance to effectively control the condensed state structure of the semirigid conjugated polymers in the process of dynamic evolution from solutions to films. It not only enriches the knowledge and understanding of both semi-rigid conjugated polymer solution behaviors and film condensed state physics based on polymer physics, but also is meaningful to practical application for conjugated polymer and other traditional polymer systems. [ABSTRACT FROM AUTHOR]

Photoelectrochemical water splitting over semiconductors offers a sustainable solar light conversion technique capable of alleviating worldwide energy crisis. Conjugated polymers have recently received increasing attention as a class of promising photoelectrode materials due to their advantages of earth‐abundance, non‐toxicity, light weight, and molecularly tunable functionalities, etc. However, the development of highly efficient organic photoelectrodes remains a big challenge. In this study, two covalent organic frameworks (COFs) incorporated 2,4,6‐triphenyl‐1,3,5‐triazine are demonstrated as excellent photocathodes for H2 production. By introducing 2,4,6‐triphenylbenene to properly create donor/acceptor pairs within COF, a significantly enhanced visible‐light photocurrent of TAPB‐TTB COF (110 µA cm−2) compared to TTA‐TTB COF (35 µA cm−2) at 0 V versus reversible hydrogen electrode (RHE) is obtained without adding organic sacrificial agent and metal cocatalysts (>420 nm). The enhanced photocurrent density is attributed to the narrowed bandgap and improved charge transfer by intramolecular donor–acceptor combination. This work highlights the great promising applications of crystalline donor–acceptor COFs as high‐efficiency organic photoelectrode for water splitting. [ABSTRACT FROM AUTHOR]

Exploration of robust and inexpensive photocatalysts for direct water splitting is highly desirable for solar energy utilization but remains a great challenge. Although some inorganic semiconductors have shown very promising activities, many suffer from low quantum efficiency and insufficient sunlight absorption or present environmental hazards. In recent years, conjugated polymer nanomaterials have rapidly become one of the most appealing candidates in photocatalysis, owing to their facile molecular functionalization, tunable optoelectronic properties, and good chemical stability. This essay highlights the recent advancement of conjugated polymer nanomaterials for solar water splitting. The research opportunities related to water photolysis together with the perspective and challenges in the field are discussed to inspire further exciting research in water splitting. [ABSTRACT FROM AUTHOR]

Organic π-conjugated polymers (CPs) have been intensively explored for a variety of critical photocatalytic applications in the past few years. Nevertheless, CPs for efficient CO2 photoreduction have been rarely reported, which is mainly due to the lack of suitable polymers with sufficient solar light harvesting ability, appropriate energy level alignment and good activity and selectivity in multi-electron-transfer photoreduction of CO2 reaction. We report here the rational design and synthesis of two novel triphenylamine (TPA) based conjugated microporous polymers (CMPs), which can efficiently catalyze the reduction of CO2 to CO using water vapor as an electron donor under ambient conditions without adding any co-catalyst. Nearly 100% selectivity and a high CO production rate of 37.15 μmol h−1 g−1 are obtained for OXD-TPA, which is significantly better than that for BP-TPA (0.9 μmol h−1 g−1) as a result of co-monomer change from biphenyl to 2,5-diphenyl-1,3,4-oxadiazole. This difference could be mainly ascribed to the synergistic effect of a decreased optical band gap, improved interface charge transfer and increased CO2 uptake for OXD-TPA. This contribution is expected to spur further interest in the rational design of porous conjugated polymers for CO2 photoreduction. [ABSTRACT FROM AUTHOR]

A conjugated polymer of poly(fluorene-co-benzothiadiazole) (PFBT) was modified by a soft segment of poly(dimethylsiloxane) (PDMS) to yield a copolymer via dynamic imine bonds. The copolymer was casted as a free-standing film, which was intrinsically flexible, stretchable, and showed tunable shape memory, healable and degradable effects. [ABSTRACT FROM AUTHOR]

Abstract: Conjugated carbonyl compounds have become the most promising type of organic electrode materials for rechargeable Li‐ion batteries because only they can achieve simultaneously high energy density, high cycling stability, and high power density. In this work, we have performed first‐principles density functional theory (DFT) calculations to explore the fundamental rules of how the electronic structure and redox properties of a typical conjugated carbonyl compound, phenanthrenequinone (PQ), are modified by adjusting the heteroaromatic building blocks. Such a molecular design strategy allows for the improvement in discharge potential while the specific capacity remains nearly unchanged. The correlation between the electronic structures and redox properties for the designed PQ derivatives is systematically discussed. It is demonstrated that the discharge potential of the PQ derivatives depends strongly on the frontier orbital levels, the electric potential, and the Li‐bonding configurations. The electrostatic potential (ESP) maps show visible displays of molecular electric structures and can be applied to understand how the redox properties of the PQ derivatives are modified by the heteroaromatic building blocks. [ABSTRACT FROM AUTHOR]

Herein we report the preparation of conjugated polymer nanoparticles via in situ Sonogashira polymerization to serve as a H2O2-degradable fluorescence/photoacoustic dual-modality contrast agent for cellular imaging. [ABSTRACT FROM AUTHOR]

2,7-Dibromofluorene monomers carrying two or four oligo(ethylene glycol) (OEG) side chains are synthesized. Heck coupling between the monomers and 1,4-divinylbenzene followed by end capping with [4-(4-bromophenoxy)butyl]carbamic acid tert-butyl ester leads to two nonionic water-dispersible poly(fluorene- alt-1,4-divinylenephenylene)s end-functionalized with amine groups after hydrolysis. In water, the polymer with a lower OEG density ( P1) has poor water dispersibility with a quantum yield of 0.24, while the polymer with a higher OEG density ( P2) possesses excellent water-dispersibility with a high quantum yield of 0.45. Both polymers show fluorescence enhancement and blue-shifted absorption and emission maxima in the presence of surfactant sodium dodecyl sulfate and dodecyltrimethylammonium bromide. The polymers are also resistant to ionic strength with minimal nonspecific interactions to bovine serum albumin. When biotin is incorporated into the end of the polymer backbones through N-hydroxysuccinimide/amine coupling reaction, the biotinylated polymers interact specifically with streptavidin on solid surface. [ABSTRACT FROM AUTHOR]

Fluorescent and biocompatible organic nanoparticles have attracted great interest in cancer detection and imaging, but the nonspecific cellular uptake has limited the detection specificity and sensitivity. Herein, the authors report the ultrasmall conjugated polymer nanoparticles (CPNs) with bright far‐red/near‐infrared emission for targeted cancer imaging with high specificity. The sizes of the ultrasmall CPNs are around 6 nm (CPN6), while large CPNs show sizes around 30 nm (CPN30). Moreover, CPN6 exhibits largely improved fluorescence quantum yield (η) of 41% than CPN30 (25%). Benefiting from the ultrasmall size, bare CPN6 shows largely suppressed nonspecific cellular uptake as compared to CPN30, while cyclic arginine‐glycine‐aspartic acid (cRGD) functionalized CPN6 (cRGD‐CPN6) possesses excellent selectivity toward αvβ3 integrin overexpressed MDA‐MB‐231 cells over other cells in cell mixtures. The faster body clearance of CPN6 over CPN30 indicates its greater potentials as a noninvasive nanoprobe for in vivo and practical applications. [ABSTRACT FROM AUTHOR]

ABSTRACT Red and near infrared (NIR) fluorescent conjugated polyelectrolytes (CPEs) have attracted increasing attention in the past few years due to their potential applications in biomedical fields. Specifically, red and NIR fluorescent CPEs with special functionalities exhibit great promises in targeted tumor cell imaging and detection of disease-related biomarkers. In addition, smart agents combining image and therapeutic actions have also been successfully demonstrated for some red and NIR emissive CPEs. In this mini review, we attempt to offer a brief description of the synthetic methods for red and NIR CPEs, and focus predominantly on the rationale behind the molecular design and their applications in biomedical research. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 519-532 [ABSTRACT FROM AUTHOR]

Molecular aggregates in conjugated polymer (CP) solution can propagate into mesoscale morphology of the relevant film and further dominate the optoelectronic property. Herein, we probed the aggregation behavior of poly(9,9- dioctylfluorene-2,7-diyl) (PFO) and studied its influence on the photophysical property in 1,2-dichloroethane (DCE) solution, where the contents of β-phase or -aggregates increased with prolonged aging time. Thereinto, high quality β-film was fabricated from DCE solution with critical aggregate time of 6 min. The film exhibited excellent surface morphology and characteristic emission of β-phase. Meanwhile, films prepared from aged DCE solutions exhibited high crystallinity, which was promising to obtain higher photoluminance efficiency and charge transport ability simultaneously. Therefore, it is significant to get deep insight into the aggregation behavior of CP, which is involved not only with the solution-processing technology of plastic device, but also with the optoelectronic property of CP. [ABSTRACT FROM AUTHOR]

In the work, the effect of PFO molecular weight change on the single chains, aggregation and β phase in the solution was investigated. Some regularity of the chain size and shape with the molecular weight change in the dynamics process were revealed and related mechanism was explored. It was found that the β phase content of high molecular weight was higher than that of low molecular weight in the range of 47,000 to 145,000 g/mol. The main reason was the intrachain interaction which led to the fold of chain itself. When PFO molecular weight was higher, the β phase can be easier formed as the intrachain interaction was stronger to fold itself to overcome the steric repulsion. Besides, single chain with lower molecular weight was more rigid than that of higher molecular weight in pure chloroform, but formed aggregation with low molecular weight was bigger and denser from the results of SLS/DLS, fractal dimension ( d f ) and TEM. It was inferred that the reason for this phenomenon was the fold of chain itself and the β phase. For chains with high molecular weight, they were comparatively long and flexible; it was easy for them to be folded to enhance the steric hindrance between different chains, so they were loosely packed. The ordered β phase occupied less volume compared to the α phase as the β conformation was more planar and packed tightly, and the proportion of β phase was more in aggregation of high molecular weight, so the aggregation size of high molecular weight was smaller than that of low molecular weight. This study is significant to control the β phase content in solution so as to increase the charge carrier mobility of the photoelectric films and the devices efficiency. [ABSTRACT FROM AUTHOR]

Stem cell-based therapies hold great promise in providing desirable solutions for diseases that cannot be effectively cured by conventional therapies. To maximize the therapeutic potentials, advanced cell tracking probes are essential to understand the fate of transplanted stem cells without impairing their properties. Herein, conjugated polymer (CP) nanodots are introduced as noninvasive fluorescent trackers with high brightness and low cytotoxicity for tracking of mesenchymal stem cells (MSCs) to reveal their in vivo behaviors. As compared to the most widely used commercial quantum dot tracker, CP nanodots show significantly better long-term tracking ability without compromising the features of MSCs in terms of proliferation, migration, differentiation, and secretome. Fluorescence imaging of tissue sections from full-thickness skin wound-bearing mice transplanted with CP nanodot-labeled MSCs suggests that paracrine signaling of the MSCs residing in the regenerated dermis is the predominant contribution to promote skin regeneration, accompanied with a small fraction of endothelial differentiation. The promising results indicate that CP nanodots could be used as next generation of fluorescent trackers to reveal the currently ambiguous mechanisms in stem cell therapies through a facile and effective approach. [ABSTRACT FROM AUTHOR]

This article summarizes the recent advances of benzothiadiazole (BT)-containing conjugated polyelectrolytes (CPEs) for biological sensing and imaging. After a brief introduction of the molecular design principles, the application of linear BT-containing CPEs as multicolor or light-up probes for visual sensing of biomolecules is reviewed. Then, linear, grafted, and hyperbranched BT-containing CPEs that can self-assemble into nanoparticles or have intrinsic 3D structures for in vitro and in vivo imaging are summarized. The future outlook of BT-containing CPEs for biomedical applications is also discussed at the end. [ABSTRACT FROM AUTHOR]

ABSTRACT A donor backbone [poly( para-divinylphenylamino)]-acceptor (cyanoacetic acid side group) type conjugated polymer ( P2) has been synthesized and used as the active material for dye-sensitized solar cells. DFT calculation shows that the insertion of vinyl link in the polymer backbone leads to a planar structure in P2 and changes the excited state significantly. Photoelectrochemical cells based on the DSSC format were fabricated using the polymers as sensitizers. The cell constructed using P2 exhibits a considerably high peak IPCE and J-V response, with an overall power conversion efficiency of 3.67%. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2958-2965 [ABSTRACT FROM AUTHOR]

A series of semiconducting polymer dots (Pdots) composed of phosphorescent Ir(III) complexes and polyfluorene units in the main polymer chains are designed, synthesized, and applied in ratiometric oxygen sensing and photodynamic cancer therapy. The ultrasmall Pdots with particle size less than 10 nm are fabricated in aqueous solution on account of amphiphilic nature of the polymers. The Pdots possess fine photostability, biocompatibility, and efficient energy transfer from the polymer main chain to the Ir(III) complex. By utilizing the excited-state energy transfer from phosphorescent Pdots to the ground state molecular oxygen, these Pdots are applied in the optical sensing of oxygen with ratiometric and naked-eye detection as well as high sensitivity in aqueous solution. The Pdots also show low cytotoxicity and can pass across the cell membrane to enter into the cytoplasm. The singlet oxygen photo-generated from the Pdots under irradiation at 488 nm can effectively induce the apoptosis and death of tumor cells for photodynamic cancer therapy in vitro. [ABSTRACT FROM AUTHOR]

The application of a time-resolved photoluminescence technique and fluorescence lifetime imaging microscopy for biosensing and bioimaging based on phosphorescent conjugated polyelectrolytes (PCPEs) containing Ir(III) complexes and polyfluorene units is reported. The specially designed PCPEs form 50 nm nanoparticles with blue fluorescence in aqueous solutions. Electrostatic interaction between the nanoparticles and heparin improves the energy transfer between the polyfluorene units to Ir(III) complex, which lights up the red signal for naked-eye sensing. Good selectivity has been demonstrated for heparin sensing in aqueous solution and serum with quantification ranges of 0-70 μM and 0-5 μM, respectively. The signal-to-noise ratio can be further improved through time-resolved emission spectra, especially when the detection is conducted in complicated environment, e.g., in the presence of fluorescent dyes. In addition to heparin sensing, the PCPEs have also been used for specific labeling of live KB cell membrane with high contrast using both confocal fluorescent cellular imaging and fluorescence lifetime imaging microscopies. This study provides a new perspective for designing promising CPEs for biosensing and bioimaging applications. [ABSTRACT FROM AUTHOR]

Development of rapid, field-portable and cost-effective sensors with high sensitivity and selectivity is of great importance for biomedical diagnostics, food safety and environmental monitoring. Silica nanoparticles (SiNPs) have great potential in sensor application due to their biocompatibility, controllable surface modification, excellent chemical stability and high specific surface area. On the other hand, conjugated polyelectrolytes (CPEs) have been widely used in sensor design due to their efficient Förster resonance energy transfer (FRET) to dyes and unique interaction with biomolecules. In this contribution, we briefly summarize the recent development of silica-related NP-based assays that incorporate CPEs as the signal amplifier or reporter. The silica-related NPs are used for probe immobilization, target recognition and separation, while CPEs provide amplified fluorescence signals and high sensitivity. These assays have been proven efficient for the detection of DNA, proteins, and small molecules through specific biorecognition events, such as DNA hybridization, antibody-antigen recognition and target-aptamer binding. [ABSTRACT FROM AUTHOR]

Cationic and anionic poly(fluorenyleneethynylene-alt-benzothiadiazole)s (PFEBTs) are designed and synthesized via Sonagashira coupling reaction to show light-up signatures toward proteins. Due to the charge transfer character of the excited states, the fluorescence of PFEBTs is very weak in aqueous solution, while their yellow fluorescence can be enhanced by polymer aggregation. PFEBTs show fluorescence turn-on rather than fluorescence quenching upon complexation with proteins. Both electrostatic and hydrophobic interactions between PFEBTs and proteins are found to improve the polymer fluorescence, the extent of which is dependent on the nature of the polymer and the protein. Changes in solution pH adjust the net charges of proteins, providing an effective way to manipulate electrostatic interactions and in turn the increment in the polymer fluorescence. In addition, the effect of protein digestion on the fluorescence of polymer/protein complexes is probed. The results indicate that electrostatic interaction induced polymer fluorescence increase cannot be substantially reduced through cleaving protein into peptide fragments. In contrast, hydrophobic interactions, mainly determined by the hydrophobicity of proteins, can be minimized by digestion, imparting a light-off signature for the polymer/protein complexes. This study thus not only highlights the opportunities of exerting nonspecific interactions for protein sensing but also reveals significant implications for biosensor design. [ABSTRACT FROM AUTHOR]

Abstract: The conjugated polyelectrolyte (CPE) poly{9,9′-bis[6″-(N,N,N-trimethylammonium)-hexylfluorene-alt-co-phenylene] dibromide} (PFPN+Br−) demonstrates a high solubility in methanol in comparison to other more hydrophilic or hydrophobic solvents. We have employed a combination of pulsed-field-gradient-NMR, photoluminescence (PL), and Raman spectroscopy to establish the conformation and aggregation behavior of PFPN+Br− in methanol, with the aim to attain information on how to design CPEs with a high solubility in a preferred solvent. We find that the diffusion coefficient and PL spectrum of PFPN+Br−, as well as the Raman-active methyl rocking mode of methanol, all exhibit a strong dependence on PFPN+Br− concentration. We rationalize our findings with a model in which PFPN+Br− forms aggregates via π–π interactions between main-chain segments, while the ionic side chains are surrounded and electrostatically screened by the methanol solvent. Accordingly, the notably high solubility of PFPN+Br− in methanol is rationalized by favorable interactions between the ionic side chains and the methanol molecules. We propose that an appropriate design of a high-solubility CPE should consider a matching of the mixed hydrophobic/hydrophilic character of the ionic side chain with that of the preferred solvent. [Copyright &y& Elsevier]

Abstract: Immunoassays are conventional methods for protein detection, which rely on specific antibody–antigen recognition. Very few strategies have been developed for signal amplification of immunoassays. In this work, we report a conjugated polymer amplified silica nanoparticle (NP)-based immunoassay for IgG detection. After immobilization of the prime antibody on the NP surface, the NPs are used to capture antigen and Cy3 labeled secondary antibody in a sandwich assay format. The presence of target antigen in solution brings the fluorescent Cy3 molecules to the NP surface. Addition of a cationic conjugated polymer further amplifies the fluorescence signal of the dye, which improves the assay sensitivity and selectivity. Within the tested concentration range, a linear response for IgG detection is observed from 0 to 1μg/mL with a detection limit of ∼1.1ng/mL. Due to the pink color of Cy3 molecules, the assay also allows naked eye detection of IgG with a detection limit of 50ng/mL. The polymer amplified NP assay represents a simple strategy for antigen detection with high sensitivity and selectivity. [Copyright &y& Elsevier]

Abstract: Methods for real time, highly selective and sensitive polynucleotide detection are of vast scientific and economic importance. Fluorescence resonance energy transfer (FRET)-based assays which take advantage of the collective response of water-soluble conjugated polymers (CPs) and the self-assembly characteristic of aqueous polyelectrolytes have been widely used for the detection of DNA, RNA, protein and small molecules. The detection sensitivity of CP-based biosensor is dependent on the signal amplification of dye emission upon excitation of CP relative to that upon direct excitation of the dye. Using cationic polyfluorene derivatives and chromophore (fluorescein or Texas Red) labeled single-stranded DNA molecules (ssDNA-C*) as donor/acceptor pairs, we show that in addition to the spectral overlap, orientation and distance between the donor and the acceptor, the energy levels and fluorescence quenching of the donor/acceptor within the polymer/DNA-C* complexes are also important factors that affect the signal output of dye emission. [Copyright &y& Elsevier]

Water Splitting: Conjugated Polymer Nanomaterials for Solar Water Splitting (Adv. Keywords: conjugated polymers; nanomaterials; solar water splitting EN conjugated polymers nanomaterials solar water splitting 1 1 1 11/12/20 20201110 NES 201110 In article number 2002474 Bin Liu and co-workers present recent progress in the design and fabrication of various types of conjugated polymer nanomaterials for photocatalytic H SB 2 sb /O SB 2 sb evolution and overall water splitting. This work also discusses the challenges and opportunities in the field of conjugated polymer-based nanophotocatalysts. [Extracted from the article]

Solvent media is crucial to the dynamic evolution process of conjugated polymer condensed state structures from solution state to film. Especially, aromatic solvent can arouse strong π-π interaction with conjugated polymer backbone. Poly(9,9-dioctylfluorene) (PFO) is a classic hairy-rod conjugated polymer. Chlorobenzene (CB) and toluene (Tol) were used as aromatic solvents, while tetrahydrofuran (THF) and chloroform (CF) were used as non-aromatic solvents. It was firstly found that PFO chain solution behaviors were closely connected to solvent aromaticity with broad concentration range from 0.005 mg/mL to 5 mg/mL. Owing to the bigger chain exclude volume in CB and Tol solvents, in dilute solution with PFO concentration ≤ 0.7 mg/mL, PFO single chains adopted more extended and rigid chain conformation than those in THF and CF solvents, thus, needed conjugated length of β conformation could be easily achieved, and β conformation could be firstly formed; PFO solution concentration increased to ≥ 1 mg/mL, chain aggregation began formation, but aggregation sizes were larger meanwhile chain packing density decreased according to the fractal dimension parameter d f ; Until PFO solution concentration increased to ≥ 3 mg/mL, only β conformation characteristic peaks began appearance in the all PL spectra. The different solution state behaviors directly affect film condensed structures. A fiber and ordered structure formed in films from CB and Tol solvents, meanwhile circular sheet and short rod-like morphology formed in films from THF and CF solvents, respectively. Solvent effect is significant not only to deeply understand the physical essence both condensed state structure formation and photoelectric performance enhancement but also to well control conjugated polymer condensed state structure to achieve photoelectric devices with high efficiency and stability. Image 1 • PFO single chain were more extended and rigid in CB and Tol aromatic solvents. • β conformation could be firstly formed in CB and Tol solvents. • Aggregation sizes were larger but chain packing density decreased in aromatic solvents owing to the bigger net excluded volume. • The different solution state behaviors directly affect film condensed structures. • Fiber and ordered structure formed from CB and Tol solvents, meanwhile circular sheet and short rod-like morphology formed from THF and CF solvents. [ABSTRACT FROM AUTHOR]

In article number 1808365, Bin Liu and co‐workers report NIR‐II light (1200 nm) excitable single‐chain conjugated polymer dots with bright NIR‐I emission (peak at ≈725 nm and quantum yield of 20.6%) for deep in vivo two‐photon imaging of an intact brain. High contrast images clearly reveal brain vasculature structure through the intact skull with a large depth of 400 μm. [ABSTRACT FROM AUTHOR]

Methods for noninvasive brain imaging are highly desirable to study brain structures in neuroscience. Two‐photon fluorescence microscopy (2PFM) with near‐infrared (NIR) light excitation is a relatively noninvasive approach commonly used to study brain with high spatial resolution and large imaging depth. However, most of the current studies require cranial window implantation or skull‐thinning methods due to attenuation of excitation light. 2PFM through intact mouse skull is challenging due to strong scattering induced by skull bone. Herein, NIR‐II light excitable single‐chain conjugated polymer dots (CPdots) with bright fluorescence in NIR‐I region (peak at ≈725 nm and quantum yield of 20.6 ± 1.0%) are developed for deep in vivo two‐photon fluorescence (2PF) imaging of intact mouse brain. The synthesized CPdots exhibit good biocompatibility, high photostability, and large two‐photon absorption cross section. The CPdots allow 2PF images acquired upon excitation at 800, 1040 and 1200 nm with the highest signal‐to‐background ratio of 208 demonstrated for 1200 nm excitation. Moreover, a 3D reconstruction of the brain blood vessel network is obtained with a large vertical depth of 400 µm through intact skull. This work demonstrates great potential of bright NIR fluorophores for in vivo deep tissue imaging. NIR‐II light (1200 nm) excitable single‐chain conjugated polymer dots with bright NIR‐I emission (peak at ≈725 nm and quantum yield of 20.6%) is developed for deep in vivo two‐photon imaging of intact mouse brain. High contrast images clearly reveal brain vasculature structure through intact skull with a large depth of 400 µm. [ABSTRACT FROM AUTHOR]

A correction to the acknowledgement section of the article "Conjugated Polymer With Rigid Donor Poly(paradivinylphenylamino) Backbone and Pendant Cyanoacetic Acid Acceptor for Dye Sensitized Solar Cells" by Zhen Fang and colleagues, published online on November 18, 2014 issue is presented.

On page 4263, D. Ding, B. Liu, K. Li, and co‐workers report a class of conjugated polymer (CP) nanodots as fluorescent trackers for long‐term in vivo tracking of transplanted mesenchymal stem cells (MSCs) to understand the mechanism in regenerative medicine. The transplanted MSCs with CP nanodot labeling could be clearly observed at a single cell level in the regenerated tissues collected from wound‐bearing mice after 3 weeks, identifying that the paracrine signaling is the primary contribution of MSCs in promoting skin regeneration. [ABSTRACT FROM AUTHOR]

Chain behavior of semi-rigid conjugated polymer in solution, correlation with condensed structure of the films and dynamic evolution in the process from solution to film are hot questions that have received close attention but have not yet solved. In this study, the scaling law obtained by laser light scattering and rheology was combined with fluorescence emission spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The chain behavior of the semi-rigid conjugated polymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT, the number-average molecular weights (M n) was 19.8 kg/mol) in solution and the condensed structure of the film were studied, the intrinsic physical relationship between the chain behavior in solution and condensed structure of the film and its dynamic evolution from solution to film were revealed. According to the concentration-dependent scaling relationship by rheology, some important parameters and chain motion characteristics in solution were revealed, such as toluene solvent was just θ solvent of F8BT, and the critical contact concentration between F8BT dilute solution and semidilute unentangled solution was found to be at 7.9 mg/mL, it firstly revealed the precursor solution concentration for film-forming (usually 10–20 mg/mL) was basically in the semidilute unentangled concentration range. The above results enrich the understanding of chain behavior in solution and the formation mechanisms of thin films condensed structure to semi-rigid conjugated polymers. The research is significant to manipulate the chain behavior in solution to construct condensed structures of the film to establish the structure-function relationship between solution state and photoelectronic device performance based on polymer physics. [Display omitted] • The size and compactness of F8BT aggregation was changed with the increase of poor solvent ratio. • The toluene was the θ solvent of F8BT in room temperature. • The critical contact concentration of F8BT chain from the Zimm model to the Rouse model was 7.9 mg/mL. [ABSTRACT FROM AUTHOR]

Polymer dots (Pdots) composed of phosphorescent Ir(III) complexes and polyfluorene units are developed by Y. L. Zhao, W. Huang, and co‐workers. On page 4823, the ultrasmall Pdots with particle sizes of less than 10 nm possess fine photostability, biocompatibility, and an efficient energy transfer capability, which are applied for the optical sensing of oxygen as well as for photodynamic cancer therapy in vitro. [ABSTRACT FROM AUTHOR]

On page 3268 Qiang Zhao, Bin Liu, Wei Huang, and co‐workers report the application of a timeresolved photoluminescent technique and fluorescence lifetime imaging microscopy for heparin sensing and bioimaging based on phosphorescent conjugated polyelectrolytes containing iridium(III) complexes to enhance the signalto‐noise ratio. This time‐resolved technique for heparin quantification in complicated media may have important clinical applications. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editors discuss various reports within the issue on topics related to the application and manufacture of fluorescent sensors from conjugated polymers.

The combination of conjugated microporous polymers (CMPs) with magnetic property was a meaningful issue in theoretical and practical study. Endowing CMPs with magnetic property can extend its application to the fields like magnetic sensor and magnetic separation. Ferrocene-based conjugated microporous polymers (Fc-CMPs) with intrinsic magnetism were constructed with ferrocene derivative as a building unit by Pd-mediated Sonogashira-Hagihara cross-coupling reaction. Fc-CMPs exhibited excellent porosity, and the BET surface area of Fc-CMPs was up to 520 m 2 /g. T he results indicated that the saturation magnetization of Fc-CMPs could be tuned by combining ferrocene derivative with monomers with different π-conjugated degree. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride (PCN) has great potential for peroxydisulfate (PDS) activation but still challenge due to the sluggish electron-hole pair dissociation and tardy charge transfer dynamics. Herein, a novel PCN-based donor-acceptor conjugated polymer (PCN/4-MI D-A) is synthesized by copolymerization of urea and 4-methoxyphenyl isothiocyanate. The obtained PCN/4-MI D-A exhibited significantly improved activity on PDS activation for nitenpyram (NTP) degradation under visible light. As a result, PDS+PCN/4-MI 75 shows the highest kinetic constants (0.115 min−1), which is ~6.8 times as that of the pure PCN. Density functional theory (DFT) calculations indicated that 4-methoxyphenyl as an electron-donating group promotes the charge separation/transfer of PCN/4-MI D-A. In addition, the PCN/4-MI D-A is more conducive to the PDS adsorption at the position where the amino group linked with 4-MI. The PCN/4-MI D-A generated abundant electrons which were subsequently transferred to the PDS by tunneling effect. This study provides a new design concept for the highly efficient PDS activation by constructed PCN-based donor-acceptor conjugated polymers. [Display omitted] • A novel PCN-based donor-acceptor conjugated polymer was fabricated. • The new photocatalysts exhibited improved activity for nitenpyram degradation. • DFT calculations indicated that 4-methoxyphenyl was an electron-donating group. • Photogenerated electrons are transferred to PDS by tunneling effect. [ABSTRACT FROM AUTHOR]

In this study, hydrogen release and uptake properties for composites of LiBH 4 with the conjugated polymer poly( p -phenylene) (PPP) were investigated. The incorporation of LiBH 4 with PPP led to a significant destabilization effect, decreasing the dehydrogenation temperature of LiBH 4 by 100 °C. Moreover, LiBH 4 could be regenerated at 450 °C under 9.0 MPa H 2 . By thorough analyses using XRD, HRTEM, FTIR, Raman, XPS as well as 11 B MAS NMR, the dehydrogenation product of LiBH 4 +PPP and the regeneration mechanism of LiBH 4 are elucidated. Also the reason of capacity degradation is discussed based on the analysis results. The formation condition of LiBH 4 was significantly moderated due to the presence of a simultaneously formed amorphous mixture of boron and carbon, which sheds light on the improvement of LiBH 4 reversibility. [ABSTRACT FROM AUTHOR]

Large two-photon absorption crosssection and high fluorescencequantum yield (QY) of a fluorescent probe is highly desirable to achievehigh resolution in two-photon excited fluorescence imaging. Takingpoly(9,9-dihexylfluorene-alt-2,1,3-benzothiadiazole)(PFBT) as an example, we report a one-step approach to synthesizePFBT loaded nanoparticles (NPs) with both large two-photon absorptioncross section and high fluorescence QY in aqueous media through amicelle and silica coprotection strategy. The PFBT loaded NPs showa two-photon absorption cross section of 1085 GM at 810 nm based onpolymer chain concentration and an emission maximum at 545 nm witha high fluorescence QY of 75%. The fluorescence lifetime investigationreveals that the high fluorescence QY is mainly due to reduced polymeraggregation and minimized environment influence on conjugated polymer(CP) fluorescence quenching. The synthesized PFBT NPs have shown goodcolloid stability and photostability as well as benign biocompatibility,which have been further applied to visualize the mouse brain vasculaturethrough intravital two-photon excited brain vascular imaging withhigh contrast. The developed micelle/silica coprotection strategyshould be generally applicable to other CP NPs with improved brightnessand stability for various biological applications. [ABSTRACT FROM AUTHOR]

Three novel conjugated polymers based on 2,2′-biimidazolehave been successfully designed and synthesized through the Suzukicoupling reactions, and their fluorescence sensing ability to metalions and anions was investigated. The emission of the two polymerswith hydrophilic side chains can be efficiently quenched by Cu2+through a photoinduced electron transfer process. Moreover,the polymer–Cu2+complexes exhibit excellent “turnon” sensing properties for detection of pyrophosphate (PPi)anion. These complex sensors possess high selectivity avoiding theinterference from other anions, very fast response (less than 3 min)to PPi, and the detection limit of about 0.17 ppm. In addition, thelinear detection range of PPi can be tuned conveniently by changingthe amount of Cu2+ions. Thus, the conjugated polymerscan be used as a novel fluorescent sensing platform, and this workprovides a new strategy for the development of PPi sensors. [ABSTRACT FROM AUTHOR]

A hyperbranched conjugated polyelectrolyte (HCPE) with a core–shell structure is designed and synthesized via alkyne polycyclotrimerization and click chemistry. The HCPE has an emission maximum at 565 nm with a quantum yield of 12% and a large Stokes shift of 143 nm in water. By virtue of its poly(ethylene glycol) shell, this polymer naturally forms spherical nanoparticles that minimize nonspecific interaction with biomolecules in aqueous solution, consequently allowing for efficient bioconjugation with anti-HER2 affibody via carbodiimide-activated coupling reaction. The resulting affibody-attached HCPE can be utilized as a reliable fluorescent probe for targeted cellular imaging of HER2-overexpressed cancer cells such as SKBR-3. Considering its low cytotoxicity and good photostability, the HCPE nanoprobe holds great promise in practical imaging tasks. This study also provides a molecular engineering strategy to overcome the intrinsic limitations of traditional fluorescent polymers (e.g., chromophore-tethered polymers and linear conjugated polyelectrolytes) for bioconjugation and applications. [ABSTRACT FROM AUTHOR]