Redox-active Polymers Research Articles

Polypeptide-based batteries toward sustainable and cyclic manufacturing

Polypeptide-based batteries toward sustainable and cyclic manufacturing

Anticancer Activity of Cell-Penetrating Redox Phospholipid Polymers.

Redox-active molecules are promising anticancer compounds because cancer cells are vulnerable to oxidative stress. Anticancer drugs are often incorporated into synthetic polymers to improve water solubility, stability, and retention in the body. Most conventional redox-active polymers are regarded as stimuli-responsive polymers, which induce the release of anticancer drugs in response to the surrounding redox environment. Here, we prepared redox phospholipid polymers composed of 2-methacryloyloxyethyl phosphorylcholine units and ferrocene or quinone units as anticancer redox polymers. Redox phospholipid polymers can disturb the intracellular redox state owing to their redox activity and cell membrane permeability. We observed that the redox potential of the polymers affected the reactivity with intracellular redox species and O2, resulting in a different impact on the viability of human cancer and normal cells. Notably, the polymer with moderate reactivity with the intracellular redox species and O2 was shown to suppress the viability of the cancer cells selectively.

An Electrochemical Sensor Based on Redox-Active Schiff Base Polymers for Simultaneous Sensing of Glucose and pH

A novel redox-active Schiff base polymer (SBPPPDA-PDA) was prepared by condensation of p-phenylenediamine with 1,10-phenanthroline-2,9-dicarbaldehyde. The structure of SBPPPDA-PDA was investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherm, and powder X-ray diffraction and electrochemical techniques. The results showed that SBPPPDA-PDA had two-dimensional lamellar structure. The electrochemical properties of SBPPPDA-PDA were characterized by cyclic voltammetry, showing several pairs of redox peaks and good catalytic ability toward oxygen reduction. On the basis of the redox-active activity of SBPPPDA-PDA, an electrochemical pH sensor was proposed based on SBPPPDA-PDA with a linear range from 2 to 9 for pH detection. With nitrogen-containing skeleton and porous structure, SBPPPDA-PDA could be used as support to load glucose oxidase (GOD). Thus, a novel ratiometric electrochemical glucose sensor was further constructed by immobilizing GOD on SBPPPDA-PDA modified electrode. The results revealed that the reduction peak of O2 decreased with the gradual addition of glucose, while the response peak of SBPPPDA-PDA at about 0.15 V almost remained. The sensor based on GOD/SBPPPDA-PDA/SPE showed a rapid response, a linear range from 22.5 μmol/L–5 mmol/L and a lower detection limit of 7.56 μmol/L for glucose.

Poly(catechol)s As Universal Electrode Materials for Advanced Organic Batteries

This decade has been witnessing the resurgence of redox-active polymer (RAP) based organic electrode materials in the quest of building large-scale, safe, economical, and sustainable electrochemical energy storage technologies (EESTs) after their brief silence. [1] Most of these RAPs mainly fall under the category of quinone, imide, organosulfur or radical polymers that have demonstrated admirable electrochemical performances. However, it is further necessary to design novel electrode materials with outstanding properties for the development of “next-generation” “high-performance” advanced organic batteries.Here, I present the macromolecular engineering of RAPs bearing catechol pendants of different functionality/composition that dictate their overall electrochemical performances in different battery technologies.Firstly, electrochemical performance of poly(catechol) cathodes in lithium-ion batteries will be presented. By tuning the pendant catechol structure, specific capacity of the homopolymer was boosted from 217 [for P(DA)] to 350 [for P(4VC)] mAh g‒1.[2] Furthermore, incorporation of cation conducting styrene sulfonates within the polymer chain in P(4VC-stat-LiSS) drastically improved the rate capability compared to P(4VC). Moreover, a voltage gain of +350 mV was demonstrated when catechol pendants were confined to an electron-withdrawing poly(ionic liquid) backbone, compared to the same redox groups groups in neutral poly(acrylamide) backbone.[3]Secondly, the application of poly(catechol) as organic cathodes for aqueous Zinc-ion batteries will be presented.[4] The Zn||P(4VC86-stat-SS14) cell in the optimized Zn(TFSI)2-H2O electrolyte simultaneously delivered high gravimetric capacity (324 mAh g‒1), high areal capacity (5.5 mAh cm‒2) at 1C, with remarkable capacity of 98 mAh g‒1 at 450C, extremely low capacity fading rate of 0.00035% per cycle over 48 000 cycles at 30 C rate and low temperature operativity (178 mAh g‒1 at –35 °C).Finally, all-polymer aqueous battery comprising poly(catechol) cathode and poly(imide) anode will be presented.[5] Interestingly, full cell exhibited tunable cell voltage depending on the salt used in the aqueous electrolyte, i.e., 0.58, 0.74, 0.89, and 0.95 V, respectively, when Li+, Zn2+, Al3+, and Li+/H+ were utilized as charge carriers. The full-cell delivered best rate performance (a sub-second charge/discharge) and cycling stability (80% capacity retention over 1000 cycles at 5 A g‒1) in Li+. Furthermore, maximum energy/power density of 80.6 Wh kganode+cathode ‒1/348 kW kganode+cathode ‒1 was achieved in Li+/H+, superior than most of the previously reported aqueous all–polymer batteries.Taking together, by the applicability of poly(catechol) as organic electrode material in different battery technologies, the following general conclusions can be drawn. They are quite universal- and accommodate reversibly numerous cations, ranging from H+, and Li+ to Al3+. This unprecedented approach is based on a simple catecholato–cation complex charge storage mechanism (n-type redox molecules). Development of such universal organic electrodes is particularly intriguing, and gaining popularity among the battery community due to the fact that it demands minimal electrode/device engineering efforts.

Macromolecular Engineering of Poly(catechol) Cathodes towards High-Performance Aqueous Zinc-Polymer Batteries.

Aqueous zinc-polymer batteries (AZPBs) comprising abundant Zn metal anode and redox-active polymer (RAP) cathodes can be a promising solution for accomplishing viable, safe and sustainable energy storage systems. Though a limited number of RAPs have been successfully applied as organic cathodes in AZPBs, their macromolecular engineering towards improving electrochemical performance is rarely considered. In this study, we systematically compare performance of AZPB comprising Zn metal anode and either poly(catechol) homopolymer (named P(4VC)) or poly(catechol) copolymer (named P(4VC86-stat-SS14)) as polymer cathodes. Sulfonate anionic pendants in copolymer not only rendered lower activation energy and higher rate constant, but also conferred lower charge-transfer resistance, as well as facilitated Zn2+ mobility and less diffusion-controlled current responses compared to its homopolymer analogue. Consequently, the Zn||P(4VC86-stat-SS14) full-cell exhibits enhanced gravimetric (180 versus 120 mAh g−1 at 30 mg cm−2) and areal capacity (5.4 versus 3.6 mAh cm−2 at 30 mg cm−2) values, as well as superior rate capability both at room temperature (149 versus 105 mAh g−1 at 150 C) and at −35 °C (101 versus 35 mAh g−1 at 30 C) compared to Zn||P(4VC)100. This overall improved performance for Zn||P(4VC86-stat-SS14) is highly encouraging from the perspective applying macromolecular engineering strategies and paves the way for the design of advanced high-performance metal-organic batteries.

A selective voltammetric pH sensor using graphitized mesoporous carbon/polyaniline hybrid system

Development of a new pH sensor system, which is simple to prepare, sensitive, selective and workable with low volume, is demanding research in biomedical and environmental studies. In the literature, organic molecules like methylene blue, toluidine blue, hydroquinone, catechol, anthraquinone and polyaniline-based redox probes have been widely used for this purpose. In general, these redox probes have easily interfered with common biochemicals such as dopamine, ascorbic acid, NADH, H2O2, cysteine, hydrazine, and some transition metal ions, etc., and in turn to marked potential and current drifts (pH-false positive response). In this work, a highly redox-active, stable and interference-free redox polymer based on poly(4-chloroaniline) (PANI(4-Cl)) modified graphitized mesoporous carbon (GMC), designated as GMC@PANI(4-Cl), has been prepared using 4-chloroaniline as a monomer in pH 7 phosphate buffer solution. The new redox polymer system showed a distinct redox peak at Eo’= 0.15 V vs Ag/AgCl with a stable voltammetric response. Transmission electron microscope analysis of the redox polymer composite had shown adhesion of black polymeric solid due to polyaniline like the molecular system as a surface layer on the GMC material. The constructed calibration plot was linear in the pH window 2-11 with a slope and regression values − 58 mV pH−1 and 0.9997, respectively. The GMC@PANI(4-Cl) modified electrode showed a sensitive and selective pH monitoring without any interference from the common biochemicals as listed above. As a practical application, pH sensing of commercial pH solutions, undiluted urine and saliva samples were demonstrated. Also, a three-in-one screen-printed carbon modified GMC@PANI(4-Cl) was explored for pH monitoring of a bacterial (E.coli) growth, which showed a comparable response with the conventional pH electrode.

A Terpyridine-Fe2+-Based Coordination Polymer Film for On-Chip Micro-Supercapacitor with AC Line-Filtering Performance.

The preparation of redox-active, ultrathin polymer films as the electrode materials represents a major challenge for miniaturized flexible electronics. Herein, we demonstrated a liquid–liquid interfacial polymerization approach to a coordination polymer films with ultrathin thickness from tri(terpyridine)-based building block and iron atoms. The as-synthesized polymer films exhibit flexible properties, good redox-active and narrow bandgap. After directly transferred to silicon wafers, the on-chip micro-supercapacitors of TpPB-Fe-MSC achieved the high specific capacitances of 1.25 mF cm−2 at 50 mV s−1 and volumetric energy density of 5.8 mWh cm−3, which are superior to most of semiconductive polymer-based micro-supercapacitor (MSC) devices. In addition, as-fabricated on-chip MSCs exhibit typical alternating current (AC) line-filtering performance (−71.3° at 120 Hz) and a short resistance–capacitance (RC) time (0.06 ms) with the electrolytes of PVA/LiCl. This study provides a simple interfacial approach to redox-active polymer films for microsized energy storage devices.

Thia-Bridged Triarylamine[4]helicene-Functionalized Polynorbor­nenes as Redox-Active pH-Sensitive Polymers

AbstractA series of thia-bridged triarylamine[4]helicene-functionalized polynorbornenes P1, P2, and P3 were synthesized via ring-opening metathesis polymerization (ROMP). The polymers obtained undergo a reversible one-electron oxidation, in both solution and solid state, responding to the pH changes in the surrounding medium showing a clear reversible electrochromic behavior.

Redox-Active Polymeric Ionic Liquids with Pendant N-Substituted Phenothiazine.

Polymers that are elastic while supporting charge transport are desirable for flexible and soft electronics. Many polymers with bulky and conjugated redox-active pendant units have high glass transition temperatures (Tg) in their neutral form that will not lead to elasticity at room temperature. Their behavior in charged form in the solid state without an electrolyte has not been extensively studied. Here, the design strategy of polymeric ionic liquid where two weakly interacting ionic groups are used to maintain a low Tg is shown to lead to flexible redox active polymers. The use of a flexible ethylene backbone and redox-active phenothiazine (PTZ)-based pendant group resulted in polymers with relatively low Tg that are electrically conductive. PTZ that was N-substituted with 2-(2-ethoxyethoxy)ethoxy)ethyl was found to promote solubility of the polymer and lower the Tg of the neutral polymer by ∼150 °C relative to that of the Tg of a variant without the N-substituent. Doping with trifluoromethanesulfonimide leads to an electrically conductive polymer without significantly increasing the Tg. Physical characterization by UV-vis-NIR spectroscopy, electron spin resonance spectroscopy, and impedance spectroscopy verified that the molecular design leads to an efficient charge hopping between the PTZ groups.

Spectroelectrochemical and electrochromic behavior of poly(methylene blue) and poly(thionine)-modified multi-walled carbon nanotubes

The increasing efforts devoted to fabricating electrochromic (EC) devices have motivated a lot of studies to develop new EC materials. Herein, we introduce two poly(phenothiazine)-type redox active polymer films as new EC materials. Poly(methylene blue) (PMB) and poly(thionine) (PTH) films were electrochemically deposited onto the transparent fluorine-doped tin oxide (FTO) electrode modified with multi-walled carbon nanotubes (MWCNTs), which are named as FTO/MWCNTs/PMB and FTO/MWCNTs/PTH, respectively. The as-prepared polymer films were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR), cyclic voltammetry (CV), and spectroelectrochemical techniques. Both polymer films exhibited EC behavior at approximately 600 nm. PMB and PTH films are blue and pale purple, respectively, in the oxidized state and change their color to colorless, if reduced at − 0.6 V. In particular, FTO/MWCNTs/PMB showed a satisfactory ΔT (24%) at 600 nm. The obtained results demonstrate that PMB and PTH, as derivatives of phenothiazine dyes, can be introduced as novel EC materials.

Concurrently increasing specific energy and suppressing self-discharge of electrochemical capacitors by complexing carbon nanotubes with redox active units-containing charged copolymers

Specific energy and self-discharge are two important performances of electrochemical capacitors. In this work, we have fabricated the composite electrodes by complexing the negatively charged carboxylated multi-walled carbon nanotubes (cMWCNT) with the redox active units-containing positively charged random copolymers. 2,2,6,6-Tetramethylpiperidinyl-N-oxyl and viologen are employed as model redox active units to exemplify the strategy of the concurrent increase of specific energy and suppression of self-discharge of a two-electrode device. The slower hydrogen and oxygen evolution reactions compared with the reactions of the redox active units lead to an increased electrolyte decomposition window, thereby giving rise to an increase in specific energy. On the other hand, the complexation between the cMWCNT and the copolymers suppresses both the redox shuttling and the cross-diffusion of the redox active units-containing polymer chains, leading to an improved performance of self-discharge. Based on the complexation between carbon nanotubes and redox active units-containing charged copolymers, this work provides a convenient and universal strategy to concurrently increase specific energy and suppress self-discharge of electrochemical capacitors.

Charge Storage Mechanism of a Quinone Polymer Electrode for Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) offer a potentially stable alternative to alkaline rechargeable zinc batteries in utilizing zinc metals for low-cost and safe energy storage. Two fundamental features of AZIBs are (1) near-neutral aqueous electrolytes, in which zinc dendrites growth is apparently suppressed compared with that in alkaline electrolytes, and (2) Zn2+ -storing cathode materials, which do not store protons in cathodes and maintain the near-neutral pH of an electrolyte throughout charge-discharge processes. Because of the importance of stored species at the cathode for the viability of a battery, the charge storage mechanism in cathode materials has been under scrutinization. Among cathode materials proposed for high-energy AZIBs, many vanadium oxides seem to store zinc-ions, while manganese oxides more often than not involve proton storage which raises concerns of pH variation of the electrolyte. Quinones have been recently proposed as versatile electrode materials for aqueous batteries. Early attempts of quinones for AZIBs have resulted in promising specific energy and cycling stability. It is therefore interesting to investigate the charge storage mechanism in these materials and assess their viability for practical applications.This work focuses on the identification of stored ions in a quinone polymer, poly(benzoquinonyl sulfide) (PBQS), as an AZIB cathode material. Possible ions to be involved in the electrode reaction include zinc ions, protons, counter anions (in this case triflate), and their hydrated forms. Spectroscopic technologies suitable for qualitative and quantitative analyses of the electrode reaction of organic materials have undergone major development in recent years. Electrochemical quartz crystal microbalance (EQCM) is an established tool to quantitatively probe the stored ions in redox-active polymers and carbon materials. Recent advancement with dissipation monitoring (EQCM-D) further strengthened the technique for characterizing softer electrodes. On the other hand, Fourier transform infrared spectroscopy (FTIR) is a standard technique for qualitative detection of chemical groups, thus a useful tool to compliment EQCM-D which may lack chemical information. In-situ FTIR has been proven effective in monitoring the electrode reactions in organic carbonyl electrodes, though the use for detection of stored ions has not been reported. Here we combine EQCM-D and FTIR techniques for a comprehensive understanding of the charge storage mechanism of PBQS in a near-neutral zinc electrolyte.

Use of biocompatible redox-active polymers based on carbon nanotubes and modified organic matrices for development of a highly sensitive BOD biosensor

This work investigated the use of redox-active polymers based on bovine serum albumin and chitosan, covalently bound to mediators neutral red and ferrocene and containing carbon nanotubes, for immobilization of Paracoccus yeei VKM B-3302 bacteria. The structures of produced polymers were studied by IR spectroscopy and scanning electron microscopy. Cyclic voltammetry and impedance spectroscopy found the electrochemical characteristics of the investigated systems: the heterogeneous electron transfer rate constant, the constant of the rate of interaction with P. yeei bacteria and the impedance. The systems containing carbon nanotubes and ferrocene-based redox-active polymer proved to be the most promising. Biosensors formed using the hybrid polymers had a high sensitivity with the lower boundary of 0.1 mg/dm3 of the detected BOD5 concentrations and a high correlation (R = 0.9916) with the standard BOD assay of surface water samples.

In-situ confinement of ultrasmall SnO2 nanocrystals into redox-active polyimides for high‐rate and long-cycling anode materials

SnO2 as a promising anode material possesses a high theoretical capacity and a safe lithiation potential; however, it suffers from low cycle stability and poor rate capability due to its nano-aggregation effect, structural instability, and sluggish electrode kinetics. Herein a one-pot hydrothermal process was developed to craft ultrasmall SnO2 nanocrystals uniformly encapsulated in the polyimide matrix through a facile in-situ polymerization. The polyimide phase can suppress the over growth of SnO2 nanoparticles while preventing from their re-aggregation through the space-confined effect during the material synthesis. The robust polyimide matrix can be also served as a protective layer to relieve the volume change of SnO2 nanoparticles and inhibit the cracks propagation throughout the whole electrode during the charge/discharge processes. Moreover, the carbonyl-contained polyimide is intrinsically redox-active, capable of affording acceptable ionic conduction ability. Remarkably, the as-fabricated SnO2@PI composite anode exhibits a reversible capacity as high as 897 mAh g−1 at 0.1 A g−1 and a high rate capability (479 mAh g−1 at 2.0 A g−1) with a higher retention (53%) than pure SnO2 (39%). The SnO2@PI anode also retains a capacity of 653 mAh g−1 at 0.5 A g−1 after 150 cycles. This work would offer an alternative strategy by incorporating metal oxide nanoparticles into the redox-active polymer matrix for advanced anode materials with high rate capability and long-term cyclability.

Mechanisms of Diffusive Charge Transport in Redox-Active Polymer Solutions

Redox-active polymers (RAPs) have pendant groups that can change their charge state due to an electrochemical driving force. There has been an interest in using RAPs as a charge storage medium in r...

Nitroxide Radical Polymer–Solvent Interactions and Solubility Parameter Determination

Redox-active polymers such as macromolecular nitroxide radicals have been studied as electrode materials for organic batteries and electronics. Polymer–solvent interactions are essential to process...

A Hybrid Redox-Active Polymer Based on Bovine Serum Albumin, Ferrocene, Carboxylated Carbon Nanotubes, and Glucose Oxidase

We used conducting redox-active polymers based on chitosan and bovine serum albumin (BSA), covalently bound to mediators ferrocene or Neutral Red, or thionine, modified by carbon nanotubes, as a base of an amperometric biosensor for determining glucose. The structure of the obtained polymers was studied by IR spectroscopy and scanning electron microscopy. Their electrochemical characteristics were studied by cyclic voltammetry. The redox-active polymer based on BSA covalently bound to ferrocene and modified by carboxylated carbon nanotubes demonstrated the most promising characteristics. The biosensor based on the selected hybrid polymer is characterized by high sensitivity, a lower limit of determined concentrations of 0.05 mM, and a high correlation coefficient (R = 0.9919) with the results of determination of glucose in human blood by an alternative method.

Probing consequences of anion-dictated electrochemistry on the electrode/monolayer/electrolyte interfacial properties

Altering electrochemical interfaces by using electrolyte effects or so-called “electrolyte engineering” provides a versatile means to modulate the electrochemical response. However, the long-standing challenge is going “beyond cyclic voltammetry” where electrolyte effects are interrogated from the standpoint of the interfacial properties of the electrode/electrolyte interface. Here, we employ ferrocene-terminated self-assembled monolayers as a molecular probe and investigate how the anion-dictated electrochemical responses are translated in terms of the electronic and structural properties of the electrode/monolayer/electrolyte interface. We utilise a photoelectron-based spectroelectrochemical approach that is capable of capturing “snapshots” into (1) anion dependencies of the ferrocene/ferrocenium (Fc/Fc+) redox process including ion-pairing with counter anions (Fc+–anion) caused by differences in Fc+–anion interactions and steric constraints, and (2) interfacial energetics concerning the electrostatic potential across the electrode/monolayer/electrolyte interface. Our work can be extended to provide electrolyte-related structure-property relationships in redox-active polymers and functionalised electrodes for pseudocapacitive energy storage.

Mussel-Inspired Redox-Active and Hydrophilic Conductive Polymer Nanoparticles for Adhesive Hydrogel Bioelectronics

HighlightsA universal strategy was proposed to producing conductive, redox-active, and hydrophilic sulfonated lignin-conductive polymer nanoparticles (CP/LS NPs).By incorporating the CP/LS NPs into hydrogel network, a good conductive, adhesive, and tough hydrogel was obtained.The redox-active NPs maintained enough catechol groups inner the hydrogel for adhesiveness.

Redox-Active Polymers Connecting Living Microbial Cells to an Extracellular Electrical Circuit.

Microbial electrochemical systems in which metabolic electrons in living microbes have been extracted to or injected from an extracellular electrical circuit have attracted considerable attention as environmentally-friendly energy conversion systems. Since general microbes cannot exchange electrons with extracellular solids, electron mediators are needed to connect living cells to an extracellular electrode. Although hydrophobic small molecules that can penetrate cell membranes are commonly used as electron mediators, they cannot be dissolved at high concentrations in aqueous media. The use of hydrophobic mediators in combination with small hydrophilic redox molecules can substantially increase the efficiency of the extracellular electron transfer process, but this method has side effects, in some cases, such as cytotoxicity and environmental pollution. In this Review, recently-developed redox-active polymers are highlighted as a new type of electron mediator that has less cytotoxicity than many conventional electron mediators. Owing to the design flexibility of polymer structures, important parameters that affect electron transport properties, such as redox potential, the balance of hydrophobicity and hydrophilicity, and electron conductivity, can be systematically regulated.