Nonconjugated Poly Research Articles

Near-Infrared Emission Beyond 900 nm from Stable Radicals in Nonconjugated Poly(diphenylmethane).

Organic radicals with narrow energy gaps are highly sought-after for the production of near-infrared (NIR) fluorophores. However, the current repertoire of developed organic radicals is notably limited, facing challenges related to stability and low fluorescence efficiency. This study addresses these limitations by achieving stable radicals in nonconjugated poly(diphenylmethane) (PDPM). Notably, PDPM exhibits a well-balanced structural flexibility and rigidity, resulting in a robust intra-/inter-chain through-space conjugation (TSC). The stable radicals within PDPM, coupled with strong TSC, yield a remarkable full-spectrum emission spanning from blue to NIR beyond 900 nm. This extensive tunability is achieved through careful adjustments of concentration and excitation wavelength. The findings highlight the efficacy of polymerization in stabilizing radicals and introduce a novel approach for developing nonconjugated NIR emitters based on triphenylmethane subunits.

Near‐Infrared Emission Beyond 900 nm from Stable Radicals in Nonconjugated Poly(diphenylmethane)

AbstractOrganic radicals with narrow energy gaps are highly sought‐after for the production of near‐infrared (NIR) fluorophores. However, the current repertoire of developed organic radicals is notably limited, facing challenges related to stability and low fluorescence efficiency. This study addresses these limitations by achieving stable radicals in nonconjugated poly(diphenylmethane) (PDPM). Notably, PDPM exhibits a well‐balanced structural flexibility and rigidity, resulting in a robust intra‐/inter‐chain through‐space conjugation (TSC). The stable radicals within PDPM, coupled with strong TSC, yield a remarkable full‐spectrum emission spanning from blue to NIR beyond 900 nm. This extensive tunability is achieved through careful adjustments of concentration and excitation wavelength. The findings highlight the efficacy of polymerization in stabilizing radicals and introduce a novel approach for developing nonconjugated NIR emitters based on triphenylmethane subunits.

Non-Conjugated Poly(Diphenylene Phthalide)-New Electroactive Material.

In organic electronics, conjugated conductive polymers are most widely used. The scope of their application is currently very wide. Non-conjugated polymers are used much less in electronics and are usually used as insulation materials or materials for capacitors. However, the potential of non-conjugated polymers is much wider, due to the fact that new electronic materials with unique electronic properties can be created on the basis of non-conjugated polymers, as well as other inorganic dielectrics. This article demonstrates the possibilities of creating electrically conductive materials with unique electronic parameters based on non-conjugated polymers. The results of the study of the sensory properties of humidity are given as examples of the practical application of the structure. The abnormal electronic properties are realized along the interface of two polymer dielectrics with functional polar groups. The submicron films of polydiphenylenephthalide were used as a dielectric. It is shown that a quasi-two-dimensional electronic structure with abnormally large values of conductivity and mobility of charge carriers occurs along the interface. These structures are often called quasi-two-dimensional electron gas (Q2DEG). This article describes the manufacturing processes of multielectrode devices. Polymer films are deposited via the spin-coating method with polymer solutions in cyclohexanone. The metal electrodes were manufactured through thermal deposition in a vacuum. Three types of metal electrodes made of aluminum, copper and chromium were used. The influence of the electron work function of contacting metals on the electronic parameters of the structure was studied. It was established that the work function decrease leads to an increase in the conductivity and mobility of charge carriers. The charge carrier parameters were estimated based on the analysis of the current-voltage characteristics within the space-charge-limited current technique. The Richardson-Schottky thermionic emission model was used to evaluate values a potential barrier at metal/organic interfaces. It was established that the change in ambient humidity strongly affects the electronic transport properties along the polymer/polymer interface. It is demonstrated that the increase in conductivity with an increase in humidity occurs due to an increase in the mobility of charge carriers and a decrease in the height of the potential barrier at the three-dimensional metal contact with two-dimensional polymer interface. The potential barrier between the electrode and the bulk of the polymer film is significantly higher than between the electrode and the quasi-two-dimensional polymer structure.

Nucleophilic Substitution Polymerization‐Induced Emission of 1,3‐Dicarbonyl Compounds as a Versatile Approach for Aggregation‐Induced Emission Type Non‐Traditional Intrinsic Luminescence†

Comprehensive SummaryNucleophilic substitution reaction and 1,3‐dicarbonyl compounds play significant roles in organic chemistry, and non‐traditional intrinsic luminescence (NTIL) has become an emerging research area. Here, we demonstrate the successful nucleophilic substitution polymerization of 1,3‐dicarbonyl compounds, including acetylacetone, 3,5‐heptanedione, methyl acetoacetate, cyclopentane‐1,3‐dione, 1,3‐indandione, 1‐phenyl‐1,3‐butanedione and dibenzoylmethane, where reactive hydrogens at α position of 1,3‐dicarbonyl compounds are involved. Through this base catalyzed nucleophilic substitution polycondensation between 1,3‐dicarbonyl compounds and α,α’‐dibromo xylene, a series of nonconjugated poly(1,3‐dicarbonyl)s have been successfully prepared with high yield (up to >99%) under mild conditions. Investigations reveal that this nucleophilic substitution polycondensation exhibits self‐accelerating effect and flexible stoichiometry characteristics, which exhibits advantages over traditional polycondensation methods. This polymerization also exhibits intriguing polymerization‐induced emission (PIE) characteristics, where nonconjugated poly(1,3‐dicarbonyl)s exhibit intriguing chemical structure dependent aggregation‐induced emission (AIE) type NTIL. This work therefore expands the monomer, method, chemical structure and property libraries of polymer chemistry, which may cause inspirations to polymerization methodology, PIE, AIE and NTIL.

Bio-inspired non-conjugated poly(carbonylpyridinium) as anode material for high-performance alkali-ion (Li+, Na+, and K+) batteries

The integration of multiple electron-accepting skeletons into polymeric structures is the forefront of materials research for high-energy sustainable energy storage. Herein, we report the synthesis of two novel non-conjugated polymers (NCP1 and NCP2) and a model small molecule (M1) incorporated with bio-derived 4-elecron-uptaking carbonylpyridinium redox-units for alkali-ion batteries. Compared to model small molecules, the polymers exhibited improved battery performance when applied as anode materials for Li-, Na-, and K-ion batteries (LIBs/SIBs/KIBs) owing to their high electrochemical activity and effective ability to suppress dissolution. By judicious selection of the benzothiadiazole redox-active linker, the performance of NCP2 was further enhanced, delivering the highest capacity and the best cycling stability; at mass loadings of up to 3.5 and 4.7 mg cm−2, the specific capacity remained at 215 and 150 mAh g−1 after 200 cycles, respectively. The Li+/Na+/K+ insertion/extraction mechanisms of NCP2 were elucidated based on experimental analyses. The insertion/extraction of Li+ was much faster than that of Na+ and K+. This study broadens the family of bio-derived carbonylpyridinium-based polymer materials for next-generation electrochemical energy storage applications.

Conjugated and Non-conjugated Polymers Containing Two-Electron Redox Dihydrophenazines for Lithium-Organic Batteries.

Organic p-type cathode materials have recently attracted increasing attention due to their higher redox potentials and rate capabilities in comparison to n-type cathodes. However, most of the p-type cathodes based on one-electron redox still suffer from limited stability and low specific capacity (< 150 mAh/g). Herein, two polymers, conjugated poly(diethyldihydrophenazine vinylene) (CPP) and non-conjugated poly(diethyldihydrophenazine ethylidene) (NCPP) containing two-electron redox dihydrophenazine, have been developed as p-type cathode materials. It is experimentally and theoretically found that the conjugated linkage among the redox centers in polymer CPP is more favorable for the effective charge delocalization on the conjugated polymer backbone and the sufficient oxidation in the higher potential region (3.3-4.2 V vs. Li/Li+). Consequently, the CPP cathode displays a higher reversible specific capacity of 184 mAh/g with excellent cycling stability.

Hydrated Hydroxide Complex Dominates the AIE Properties of Nonconjugated Polymeric Luminophores.

Nontraditional intrinsic luminescence (NTIL) which always accompanied with aggregation-induced emission (AIE) features has received considerable attention due to their importance in the understanding of basic luminescence principle and potential practical applications. However, the rational modulation of the NTIL of nonconventional luminophores remains difficult, on account of the limited understanding of emission mechanisms. Herein, the emission color of nonconjugated poly(methyl vinyl ether-alt-maleic anhydride) (PMVEMA) can be readily regulated from blue to red by controlling the alkalinity during the hydrolysis process. The nontraditional photoluminescence with AIE property is from the new formed p-band state, resulting from the strong overlapping of p orbitals of the clustered O atoms through space interactions. Hydrated hydroxide complexes embedded in the entangled polymer chain make big difference on the clustering of O atoms which dominates the AIE property of nonconjugated PMVEMA. These new insights into the photoluminescence mechanism of NTIL should stimulate additional experimental and theoretical studies and can benefit the molecular-level design of nontraditional chromophores for optoelectronics and other applications.

Unveiling the Photoinduced Recovery Mystery in Conjugated Polymer-Based Transistor Memory.

A straightforward mechanism for the photorecovery behavior of photoresponsive nonvolatile organic field-effect transistor (OFET) memories is proposed by employing a commercially available conjugated polymer, the poly(9,9-dioctylfluorene) (PFO), the conjugated monomer fluorene (FO), and the nonconjugated poly(vinyl alcohol) (PVA), as charge storage layers beneath the semiconducting pentacene layer. As photoexcitons are generated upon light exposure, the respective charges recombine with the trapped charges in electrets and neutralize the memory device. However, whether the excitons are generated in the semiconducting layer or the electret part, the origin that mainly governs the photorecovery behavior remains unclear. In this study, we show that when PVA, a nonphotoactive electret, replaces PFO the photorecovery behavior is totally absent, and it confirms the photorecovery behavior dominated by the excitons in situ generated in a charged electret. Moreover, PFO as a photoactive electret, exhibiting an excellent hole-trapping ability over 24 h in the dark and high Ion/Ioff current ratio of 108, has successfully demonstrated rapid photoinduced recovery under UV light. The devices also display a reliable switching ability between electrical charge trapping and optical recovery cycles for optical-recording application. This report presents a clear understanding behind photorecovery phenomena that demonstrates useful guidance to boost the development of photoactive OFET memories based on conjugated polymer electrets.

AIE-active non-conjugated poly(N-vinylcaprolactam) as a fluorescent thermometer for intracellular temperature imaging.

Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with π-π conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly(N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 °C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.

Benzoladderene Mechanophores: Synthesis, Polymerization, and Mechanochemical Transformation

We have previously reported a polymechanophore system, polyladderene, which underwent dramatic bond rearrangement in response to mechanical force to yield semiconducting polyacetylene. Herein, we report the scalable synthesis of benzoladderenes as new mechanophore monomers. Ring-opening metathesis polymerization of benzoladderenes yielded homopolymers and block copolymers with controlled molecular weights and low dispersity. The resulting nonconjugated poly(benzoladderene) was mechanochemically transformed into conjugated poly( o-phenylene-hexatrienylene) by sonication, with degrees of transformation up to 40-45%. These benzoladderenes and their resulting polymers are easier to synthesize than the polyladderene system and allow mechanochemical generation of conjugated polymersbeyond polyacetylene.

Self-Assembling Nonconjugated Poly(amide-imide) into Thermoresponsive Nanovesicles with Unexpected Red Fluorescence for Bioimaging.

Nonconjugated red fluorescent polymers have been increasingly studied to improve the biocompatibility and penetration depth over conventional fluorescent materials. However, the accessibility of such polymers remains challenging due to the scarcity of nonconjugated fluorophores and lacking relevant mechanism of red-shifted fluorescence. Herein, we discovered that the combination of hydrogen bonding and π-π stacking interactions provides nonconjugated poly(amide-imide) with a large bathochromic shift (>100 nm) from blue-green fluorescence to red emission. The amphiphilic PEGylated poly(amide-imide) derived from in situ PEGylation self-assembled into nanovesicles in water, which isolated the aminosuccinimide fluorophore from the solvents and suppressed the hydrogen bonds formation between aminosuccinimide fluorophores and water. Therefore, the fluorescence of PEGylated poly(amide-imide) in water was soundly retained. Furthermore, the strong hydrogen bonding and hydrophobic interactions with water provided PEGylated poly(amide-imide) with a reversible thermoresponsiveness and presented a concentration-dependent behavior. Finally, accompanied by the excellent biostability and photostability, PEGylated poly(amide-imide) exhibited as a good candidate for cell imaging.

Poly(aryl amino ketone)-based materials with excellent electrochromic and electrofluorochromic behaviors

In recent years, electrochromic materials have attracted much attention for application in many fields, such as smart windows, mirrors, optical displays, and camouflage materials. Due to the advantages of short switching time, easy color-tuning, and high optical contrast ratio, polymer materials have great value for this research. In this work, a series of nonconjugated poly(aryl amino ketone) (PAAK)-based materials with carbazol-9-yl triphenylamine (CzTPA) units were designed and synthesized. These polymers were first used to research electrochromism (EC) and electrofluorochromism (EFC). In spite of the fact that they are nonconjugated polymers, they still exhibited some exciting electrochromic and electrofluorochromic performances, such as good switching time (the fastest speed can reach 1.91 s for coloring and 0.66 s for bleaching), high optical contrast (PAAK-tBu-CzTPA's highest Δ%T is 87% at 730 nm) and rapid fluorescence response (1.42 s for quenching).

Effect of Nonionic Conjugated Matrix Polymer and P-Dopant on Carbon Nanotube Aggregation and Thermoelectric Properties

ABSTRACTThe properties of a mixed metallic and semiconducting carbon nanotube (CNT) sample dispersed in nonconjugated poly(methyl methacrylate) (PMMA) and conjugated poly(bisdodecylquaterthiophene) (PQT12) were compared, with and without p-doping by NOBF4. The CNTs were distributed much more evenly, and percolated at much lower concentrations (ca. 2%), in the PMMA as compared to PQT12, as judged by optical microscopy and electronic conductivity measurements. Seebeck coefficients (S) obtained on the PMMA samples indicated dominance by the metallic fraction, with values &lt;10 µV/K. Composites made with PQT12 alone showed slightly higher values of S, but with the addition of 3 wt % dopant, S increased markedly to about 100 µV/K at 5-10% CNT fractions, while conductivity was unexpectedly low. As the CNT fraction in the doped sample was increased to 25-30%, conductivity approached that of the comparable concentration of CNTs in PMMA, while S, ca. 15 µV/K, was still higher than that measured in PMMA. The observations inform interpretations of CNT-polymer composite thermoelectric data, pointing out the roles of conjugated main chains and added dopants in modulating contributions of CNTs to thermoelectric composite performance.

Tenfold increase in efficiency from a reference blue OLED

Starting from a reference single-layer light-emitting diode based on the blue phosphorescent bis-cyclometallated iridium complex FIrpic as guest, hosted in a PVK (non-conjugated poly(vynilcarbazole)) matrix, different strategies are followed to improve the efficiency of the devices through the combination of solution processed and evaporated layers. Injection of charges from the electrodes has been varied by using different conductive PEDOT: PSS as hole injection layer and a nanoscale Cs2CO3 interlayer as electron injection and hole-blocking film. Furthermore, a separated electron injection/hole blocking evaporated layer, TPBi or 3TPYMB, is introduced in double-layer devices to enhance the minority carriers (electrons) and also to confine holes to the emissive layer. All these modifications lead to an approximate tenfold improvement in efficiency from the initial reference device.

Highly Efficient Inverted Perovskite Solar Cells With Sulfonated Lignin Doped PEDOT as Hole Extract Layer.

Sulfonated-acetone-formaldehyde (SAF) was grafted with alkali lignin (AL) to prepare grafted sulfonated-acetone-formaldehyde lignin (GSL). Considering the rich phenolic hydroxyl groups in GSL, we detected a hole mobility of 2.27 × 10(-6) cm(2) V(-1) s(-1) with GSL as a hole transport material by space-charge-limited current model. Compared with nonconjugated poly(styrene sulfonic acid), GSL was applied as p-type semiconductive dopant for PEDOT to prepare water-dispersed GSL. GSL shows enhanced conductivity compared with that of PSS. Simultaneously, the enhanced open-circuit voltage, short-circuit current density, and fill factor are achieved using GSL as a hole extract layer (HEL) in sandwich-structure inverted perovskite solar cells. The power conversion efficiency is increased to 14.94% compared with 12.6% of PSS-based devices. Our results show that amorphous GSL is a good candidate as dopant of PEDOT, and we provide a novel prospective for the design of HEL based on lignin, a renewable biomass and phenol derivatives.

Aggregation-induced emission of non-conjugated poly(amido amine)s: Discovering, luminescent mechanism understanding and bioapplication

It is found that the fluorescence of aliphatic poly(amido amine)s including linear and hyperbranched ones can be dramatically enhanced by simple aggregation of polymer chains, attributing to the formation of a variety of intra- and interchain clusters with shared lone-pair electrons and the restriction of intramolecular motions. Thanks to the combination of strong solid fluorescence and excellent biocompatibility, these non-conjugated polymers become promising candidates for bioimaging such as bacterial detection. This finding not only extends the aggregation-induced emission (AIE) systems from conjugated compounds to non-conjugated materials, which expands the bioapplication range of AIE systems, but also sheds light on the exploration of novel unconventional luminogens.

White light emission transparent polymer nanocomposites with novel poly(p-phenylene vinylene) derivatives and surface functionalized CdSe/ZnS NCs

A series of new polymers with conjugated poly(p-phenylene vinylene) units and non-conjugated poly(p-xylylene) units containing vinyl and carboxyl groups were synthesized. The monodisperse CdSe/ZnS nanocrystals with a red light emission were prepared by using the phosphine-free precursors. A novel fluorescent polymer and 5-(2-methacryloylethyloxymethyl)-8-quinolinol were dispersed in vinyl monomers containing CdSe/ZnS NCs to successfully fabricate transparent bulk nanocomposites by in situ polymerization. The 5-(2-methacryloylethyloxymethyl)-8-quinolinol molecules can be coordinated to the surface of CdSe/ZnS nanocrystals to form a metalloquinolate with green light emission at about 500 nm, while the red light emission of nanocrystals remained after the polymerization process. The efficient white light emitting polymer nanocomposites with color coordinates (0.32, 0.34) can be obtained when the weight ratio of nanocrystals to 5-(2-methacryloylethyloxymethyl)-8-quinolinol is 10:1. A charge transfer from the photoexcited metalloquinolates to the nanocrystals was observed in the system.

Enhanced green electrophosphorescence by using polyfluorene host via interfacial energy transfer from polyvinylcarbazole

For green-emitting Ir complex-doped polymer devices, high efficiencies have been achieved only when non-conjugated poly( N-vinylcarbazole) (PVK) was used as the host polymer. It is commonly believed that conjugated polyfluorenes (PFO) are not suitable for the use as host of green phosphorescent complexes due to the presence of the low-lying triplet state. In this paper we reported that despite very inefficient PL phosphorescent emission of Ir(Bu-PPy) 3 in the PFO films, strong green electroluminescence (EL) and high device efficiencies have been observed for devices from such blend films when multilayer device with PVK was used as anode buffer. We analyze the PL spectra in steady state and transient response and found that the energy transfer via PVK interlayer plays important role in the efficient EL performance. This fact clearly indicates the efficient electrophosphorescence might be achieved even if the triplet energy of phosphorescence dye is higher than that of the host. These findings could significantly broaden our selection in polymer hosts for phosphorescent devices.

Highly Conductive Poly(phenylene thienylene)s: m-Phenylene Linkages Are Not Always Bad

Two isomeric polymers, which contain meta- or para-phenylene linkages between conducting segments, have been synthesized and compared by electrochemical methods. The nonconjugated poly(1,5-diacetoxy-m-phenylene tetrathienylene) (PMPT-OAc) showed similar electroactivity to the para-isomer, poly(2,5-diacetoxy-p-phenylene tetrathienylene) (PPPT-OAc), in the cyclic voltammetry and in-situ conductivity measurements. Spectroelectrochemistry showed a similar buildup of sub-band-gap electronic transitions. Deacetylation of the polymers was performed successfully by reaction with hydrazine, producing PMPT-OH and PPPT-OH. Both phenol-substituted polymers exhibited greater electroactivity than the acetoxy-substituted polymers. In addition, the phenol substituents were found to lower the “turn-on” potential in the conductivity−potential profile for PMPT-OH, but not for PPPT-OH. An alkoxy-substituted PMPT-OMe shows electroactivity similar to that of PMPT-OAc in the cyclic voltammetry, in-situ conductivity, and spectroelectrochemistry.

Photoinitiated thermolysis of poly(phenylenevinylene) precursor and photochemical doping of poly(phenylenevinylene)

AbstractThe photoinitiated elimination of methoxy groups of poly(p‐phenylene‐1‐methoxyethylene) and the photochemical doping of the resulting poly(phenylenevinylene) (PPV) were investigated. Upon irradiation and then heat treatment at 150°C, poly(p‐phenylene‐1‐methoxyethylene) containing triphenylsulfonium hexafluoroantimonate was converted to PPV. The resulting PPV was observed to be conductive, and its conductivity was 10−2–10−3 S/cm. By a lithographic procedure, we produced a conducting pattern doped photochemically in a nonconjugated poly(p‐phenylene‐1‐methoxyethylene) matrix.