Aniline Oligomers – Architecture, Function and New Opportunities for Nanostructured Materials

Competitive proton-trapping strategy enhanced anti-freezing organohydrogel fibers for high-strain-sensitivity wearable sensors

Stretchable organohydrogel fibers are attracting considerable interest for next-generation flexible and wearable soft strain sensors due to their excellent stability in harsh environments. However, due to the uniformly distributed ions and reduced number of carriers in the whole material, the sensitivity of organohydrogel fibers under subzero temperature is not desirable, which significantly hinders their practical application. Herein, a newly competitive proton-trapping strategy was designed to obtain anti-freezing organohydrogel fibers for high-performance wearable strain sensors via a simple freezing-thawing process, in which tetraaniline (TANI), serving as the proton trapper, and representing the shortest repeated structural unit of polyaniline (PANI), was physically crosslinked with polyvinyl alcohol (PVA) (PTOH). The as-prepared PTOH fiber exhibited an outstanding sensing performance at -40 °C due to the unevenly distributed ion carriers and the highly breakable proton-migration pathways, with a high gauge factor of 24.6 at a strain of 200-300%. Moreover, the existence of hydrogen bonds between the TANI and PVA chains endowed PTOH with a high tensile strength (1.96 MPa) and toughness (8.0 MJ m-3). Accordingly, strain sensors made from PTOH fibers and knitted textiles could monitor human motions rapidly and sensitively, demonstrating their potential as wearable anti-freezing anisotropic strain sensors.

Structurally well-defined conjugated meso-aminoporphyrin oligomers analogous to polyanilines

Polyaniline, which is formed by the oxidative polymerization of aniline, is a widely explored conducting polymer with several stable oxidation states, and can be applied in advanced materials, including sensing devices and electrochemical catalysts. The marriage of polyanilines with the diverse chemistry of porphyrins is expected to confer new properties, including a combination of electrical, optical, magnetic and chemical properties. Herein, we demonstrate that meso-aminodiarylporphyrin, a porphyrin analogue of aniline, undergoes oxidative oligomerization in an acidic solution under an oxygen atmosphere to yield stable oligomeric products that are analogous to fully oxidized polyanilines. The so-formed oligomers are composed of the same number of electron-rich porphyrinoid and electron-deficient quinoid moieties, and they exhibit a broad electronic absorption band in the near infrared (NIR) region, which is attributable to intramolecular charge transfer (ICT) transition from electron-rich porphyrinoid moieties to electron-deficient quinoid ones. The quinoid moieties in the oligomers could be reversibly reduced using sodium ascorbate to obtain all-porphyrinoid oligomers that resemble fully reduced polyanilines. The fully reduced oligomers do not exhibit the NIR ICT band. Furthermore, three types of partially reduced tetramers consisting of a single quinoid moiety were also obtained, among which two interconverted in solution. Their interconversion was significantly accelerated in the presence of a protic solvent. This result is consistent with the high electron conductivity of partially oxidized polyanilines following their protonation.

Fe Single-Atom Catalyst for Cost-Effective yet Highly Efficient Heterogeneous Fenton Catalysis

High energy consumption in pyrolyzing precursors for catalyst preparation would limit the application of nitrogen-doped carbon-based single-atom catalysts in actual pollutant remediation. Herein, we report an Fe single atom (7.67 wt %) loaded polyaniline catalyst (Fe-PANI) prepared via a simple impregnation process without pyrolysis. Both experimental characterizations and density functional theory calculations demonstrated that isolated -N═ group sites can fasten Fe atoms through Fe-N coordination in PANI, leading to a high stability of Fe atoms in a heterogeneous Fenton reaction. Highly dispersive yet dense -N═ groups in PANI can be protonated to be adsorption sites, which largely reduce the migration distance between reactive radicals and organics. More significantly, frontier molecular orbitals and spin-density distributions reveal that electrons can transfer from reduction groups of PANI to an Fe(III) site to accelerate its reduction. As a result, a remarkably boosted degradation behavior of organics under near-neutral conditions (pH 6), with low H₂O₂ concentration, was achieved. This cost-effective Fe-PANI catalyst with high catalytic activity, stability, and adsorption performance has great potential for industrial-level wastewater treatment.

Biodegradable polymeric materials for flexible and degradable electronics

Biodegradable electronics have great potential to reduce the environmental footprint of electronic devices and to avoid secondary removal of implantable health monitors and therapeutic electronics. Benefiting from the intensive innovation on biodegradable nanomaterials, current transient electronics can realize full components’ degradability. However, design of materials with tissue-comparable flexibility, desired dielectric properties, suitable biocompatibility and programmable biodegradability will always be a challenge to explore the subtle trade-offs between these parameters. In this review, we firstly discuss the general chemical structure and degradation behavior of polymeric biodegradable materials that have been widely studied for various applications. Then, specific properties of different degradable polymer materials such as biocompatibility, biodegradability, and flexibility were compared and evaluated for real-life applications. Complex biodegradable electronics and related strategies with enhanced functionality aimed for different components including substrates, insulators, conductors and semiconductors in complex biodegradable electronics are further researched and discussed. Finally, typical applications of biodegradable electronics in sensing, therapeutic drug delivery, energy storage and integrated electronic systems are highlighted. This paper critically reviews the significant progress made in the field and highlights the future prospects.

Precursor Customized Assembly of Wafer-scale Polymerized Aniline Thin-films for Ultrasensitive NH3 Detection

2D conducting polymer thin-film recently has garnered numerous interests as a means of combining the molecular aggregate ordering and promoting in-plane charge transport for large-scale/flexible organic electronics. However, it remains far from satisfactory for conducting polymer chains to achieve desirable surface topography and crystallinity due to lack of control over the precursor involved interfacial assembly. Herein, wafer-size polyaniline (PANI) and tetra-aniline (TANI) thin-film has been developed via a controlled interfacial synthesis with customized surface morphology and crystallinity through two typical aniline precursors selective polymerization. Two crucial competing assembly mechanisms, a) direct interfacial polymerization, b) solution polymerization and subsequent interfacial assembly, were investigated to play a vital role in determining elemental chain length and aggregate architecture. The optimal PANI thin-film manifests ultra-flat surface topography and unambiguous crystalline domains, which also enabling fascinating ammonia sensing capability with 31.4%/ppm sensitivity, fast response time (88 s) with astonishing selectivity, repeatability and recovery capability. The thus-demonstrated strategy with wafer-scale processing potential and flexible micro-device offers a promising route for large-scale manufacturing thin-film organic electronics. This article is protected by copyright. All rights reserved.

Mediation of water-soluble oligoaniline by phenol in the aniline-persulfate system under alkaline conditions

Although synthesis of oligoaniline (OANI) by persulfate and aniline has been investigated in the recent years, the impact of phenol on the synthesized soluble OANI is still not clear. In this study, our results indicate that phenol and pH mediate the production of the blue water-soluble OANI (OANI_blue) in the reaction between sodium persulfate (SPS) and aniline under alkaline conditions, and the yields of OANI_blue increase with increasing concentrations of phenol and pH values. Quenching experiments rule out the contributions of SO₄˙^- and ˙OH to aniline oxidation and imply that the non-radical activation of SPS is an important pathway in the formation of OANI_blue. MALDI-TOF-MS analysis indicates that phenol apparently inhibits the polymerization degree of aniline in that the molecular weights of OANI_blue gradually decrease from 1586.4 to 684.6 when phenol is increased from 0 to 2.0 mM. FTIR and Raman analyses confirm the structure of aniline oligomers in OANI_blue and indicate that phenol inhibits the phenazine-like structure in OANI_blue and facilitates the transformation of benzenoid rings to quinoid rings in the oxidation products. However, simultaneous activation of SPS by phenol and aniline is likely to occur in the reaction system with the formation of PhNH˙, as indicated by DFT calculations. The high scavenging reactivity of phenol towards both PhNH₂˙⁺ and PhNH˙ implies that PhNH₂˙⁺ and PhNH˙ are not the intermediates in the formation of OANI_blue. DFT calculations also reveal that apart from the one-electron transfer pathway between aniline and SPS, the two-electron transfer pathway is also likely to occur in the presence of phenol, resulting in the formation of PhNH⁺/PhN˙˙ without producing PhNH₂˙⁺ and PhNH˙. The produced PhNH⁺/PhN˙˙ intermediates then couple with aniline, PhNH⁺, aminophenyl sulfate and its hydrolysate to form dimers, trimers, oligomers, and eventually OANI_blue. This study not only describes a novel method to prepare water-soluble OANI, but also gives new insight on the importance of phenol in the production of OANI_blue.

Amphiphilic Peptoid-Directed Assembly of Oligoanilines into Highly Crystalline Conducting Nanotubes

It is reported herein the synthesis of a novel amphiphilic diblock peptoid bearing a terminal conjugated oligoaniline and its self-assembly into small-diameter (D ≈ 35 nm) crystalline nanotubes with high aspect ratios (>30). It is shown that both tetraaniline (TANI)-peptoid and bianiline (BANI)-peptoid triblock molecules self-assemble in solution to form rugged highly crystalline nanotubes that are very stable to protonic acid doping and de-doping processes. The similarity of the crystalline tubular structure of the nanotube assemblies revealed by electron microscopy imaging, and X-ray diffraction analysis of the nanotube assemblies of TANI-functionalized peptoids and nonfunctionalized peptoids showed that the peptoid is an efficient ordered structure directing motif for conjugated oligomers. Films of doped TANI-peptoid nanotubes has a dc conductivity of ca. 95 mS cm^-1 , while the thin films of doped un-assembled TANI-peptoids show a factor of 5.6 lower conductivity, demonstrating impact of the favorable crystalline ordering of the assemblies on electrical transport. These results demonstrate that peptoid-directed supramolecular assembly of tethered π-conjugated oligo(aniline) exemplify a novel general strategy for creating rugged ordered and complex nanostructures that have useful electronic and optoelectronic properties.

Linear and star-shaped π-conjugated oligoanilines: a review on molecular design in syntheses and properties

Molecular Design and Synthesis of Linear and Star-shaped π-conjugated Oligoanilines with reversible optoelectrochemical properties.

In-Out Surface Modification of Halloysite Nanotubes (HNTs) for Excellent Cure of Epoxy: Chemistry and Kinetics Modeling

In-out surface modification of halloysite nanotubes (HNTs) has been successfully performed by taking advantage of 8-hydroxyquinolines in the lumen of HNTs and precisely synthesized aniline oligomers (AO) of different lengths (tri- and pentamer) anchored on the external surface of the HNTs. Several analyses, including FTIR, H-NMR, TGA, UV-visible spectroscopy, and SEM, were used to establish the nature of the HNTs’ surface engineering. Nanoparticles were incorporated into epoxy resin at 0.1 wt.% loading for investigation of the contribution of surface chemistry to epoxy cure behavior and kinetics. Nonisothermal differential scanning calorimetry (DSC) data were fed into home-written MATLAB codes, and isoconversional approaches were used to determine the apparent activation energy (E_α) as a function of the extent of cure reaction (α). Compared to pristine HNTs, AO-HNTs facilitated the densification of an epoxy network. Pentamer AO-HNTs with longer arms promoted an Excellent cure; with an E_α value that was 14% lower in the presence of this additive than for neat epoxy, demonstrating an enhanced cross-linking. The model also predicted a triplet of cure (m, n, and ln A) for autocatalytic reaction order, non-catalytic reaction order, and pre-exponential factor, respectively, by the Arrhenius equation. The enhanced autocatalytic reaction in AO-HNTs/epoxy was reflected in a significant rise in the value of m, from 0.11 to 0.28. Kinetic models reliably predict the cure footprint suggested by DSC measurements.

A unique amphiphilic triblock copolymer, nontoxic to human blood and potential supramolecular drug delivery system for dexamethasone

The drug delivery system (DDS) often causes toxicity, triggering undesired cellular injuries. Thus, developing supramolecules used as DDS with tunable self-assembly and nontoxic behavior is highly desired. To address this, we aimed to develop a tunable amphiphilic ABA-type triblock copolymer that is nontoxic to human blood cells but also capable of self-assembling, binding and releasing the clinically used drug dexamethasone. We synthesized an ABA-type amphiphilic triblock copolymer (P2L) by incorporating tetra(aniline) TANI as a hydrophobic and redox active segment along with monomethoxy end-capped polyethylene glycol (mPEG2k; Mw = 2000 g mol-1) as biocompatible, flexible and hydrophilic part. Cell cytotoxicity was measured in whole human blood in vitro and lung cancer cells. Polymer-drug interactions were investigated by UV-Vis spectroscopy and computational analysis. Our synthesized copolymer P2L exhibited tuned self-assembly behavior with and without external stimuli and showed no toxicity in human blood samples. Computational analysis showed that P2L can encapsulate the clinically used drug dexamethasone and that drug uptake or release can also be triggered under oxidation or low pH conditions. In conclusion, copolymer P2L is nontoxic to human blood cells with the potential to carry and release anticancer/anti-inflammatory drug dexamethasone. These findings may open up further investigations into implantable drug delivery systems/devices with precise drug administration and controlled release at specific locations.

Bicyclic Bridgehead Phosphoramidite-Based Hybrid Diphosphorus Ligands: Design, Synthesis, and Application in Catalytic Asymmetric Hydrogenation

A strategy for chiral ligand design has been developed that allows for incorporation of an achiral bicyclic bridgehead phosphoramidite to generate a class of hybrid diphosphorus ligands for high activity and asymmetric control. Using this concept, a series of chiral phosphine-phosphoramidite ligands bearing the sole chirality at the ligand backbone have been prepared and successfully employed in the Rh-catalyzed asymmetric hydrogenation of 2-vinylanilides for the synthesis of optically active anilines bearing an ortho-tertiary benzylic stereocenter.

Comparative Studies of CPEs Modified with Distinctive Metal Nanoparticle-Decorated Electroactive Polyimide for the Detection of UA

In this present work, an electrochemical sensor was developed for the sensing of uric acid (UA). The sensor was based on a carbon paste electrode (CPE) modified with electroactive polyimide (EPI) synthesized using aniline tetramer (ACAT) decorated with reduced nanoparticles (NPs) of Au, Pt, and Ag. The initial step involved the preparation and characterization of ACAT. Subsequently, the ACAT-based EPI synthesis was performed by chemical imidization of its precursors 4,4′-(4.4′-isopropylidene-diphenoxy) bis (phthalic anhydride) BPADA and ACAT. Then, EPI was doped with distinctive particles of Ag, Pt and Au, and the doped EPIs were abbreviated as EPIS, EPIP and EPIG, respectively. Their structures were characterized by XRD, XPS, and TEM, and the electrochemical properties were determined by cyclic voltammetry and chronoamperometry. Among these evaluated sensors, EPI with Au NPs turned out the best with a sensitivity of 1.53 uA uM⁻¹ UA, a low limit of detection (LOD) of 0.78 uM, and a linear detection range (LDR) of 5–50 uM UA at a low potential value of 310 mV. Additionally, differential pulse voltammetric (DPV) analysis showed that the EPIG sensor showed the best selectivity for a tertiary mixture of UA, dopamine (DA), and ascorbic acid (AA) as compared to EPIP and EPIS.

Crosslinked porous polyimides: structure, properties and applications

Porous polyimides (pPIs) represent a fascinating class of porous organic polymers (POPs). Here the properties and functions of amorphous and crystalline pPIs are reviewed, and applications contributing to solutions to global challenges highlighted.

Mechanistic Study of Domino Rearrangement-Promoted Meta C-H Activation in 2-Methyl-N-methoxyaniline via Cu(NHC)+: Motivation and Selectivity

Here we report a detailed theoretical study of the mechanism of Cu⁺-catalyzed domino rearrangement of 2-methyl-N-methoxyaniline with a deep understanding of the unique motivation and selectivity of these migrations. We find that the Cu⁺ catalyst accelerates the [1,3]-methoxy migration to the methyl-bound ortho position of umpolung phenyl. The following domino transfer prefers methyl [1,2]-migration, and the rate-determining step for the whole reaction is the transfer of a proton from the phenyl ring to amine to finish the catalytic cycle.

The Applications of Solid-State NMR to Conducting Polymers. The Special Case on Polyaniline

Polyaniline is one of the most well studied conducting polymers due to its advanced electrical, chemical, redox and morphological properties. The high conductivity of regular polyaniline, when partially oxidized and doped under acidic conditions, has been associated with the formation of unique electronic states known as polarons and bipolarons. Alternative aniline oxidation products and interesting nanotube and nanorod forms have been observed as the synthesis conditions are varied. Solid-state NMR has offered great opportunities for structural investigations and the determination of molecular dynamics in such a complex and diverse material. This review summarizes various applications of solid-state NMR techniques to polyaniline and its derivatives and the information that can be obtained by solid-state NMR.

Tunable Self-Assembled Nanostructures of Electroactive PEGylated Tetra(Aniline) Based ABA Triblock Structures in Aqueous Medium

PEGylated tetra(aniline) ABA triblock structure PEG-TANI-PEG (2) consisting of tetra(aniline) (TANI) and polyethylene glycol (PEG) was synthesized by coupling the tosylated-PEG to boc-protected NH2/NH2 TANI (1) through a simple nucleophilic substitution reaction. Deprotection of 2 resulted in a leucoemeraldine base state of TANI (2-LEB), which was oxidized to stable emeraldine base (2-EB) state. 2-EB was doped with 1 M HCl to emeraldine salt (2-ES) state. FTIR, 1H and 13C NMR and UV-Vis-NIR spectroscopy, and MS (ESI) was used for structural characterization. The synthesized triblock structure exhibited good electroactivity as confirmed by CV and UV-Vis-NIR spectroscopy. Self-assembling of the triblock structure in aqueous medium was assessed by DLS, TEM, and SEM. Spherical aggregates were observed with variable sizes depicting the effect of concentration and oxidation of 2-LEB. Further, the aggregates showed acid/base sensitivity as evaluated by doping and dedoping of 2-EB with 1 M HCl and 1 M NH4OH, respectively. Future applications in drug delivery and sensors are envisaged for such tunable self-assembled nanostructures in aqueous media.

Direct grafting of tetraaniline via perfluorophenylazide photochemistry to create antifouling, low bio-adhesion surfaces

Conjugated polyaniline has shown anticorrosive, hydrophilic, antibacterial, pH-responsive, and pseudocapacitive properties making it of interest in many fields. However, in situ grafting of polyaniline without harsh chemical treatments is challenging. In this study, we report a simple, fast, and non-destructive surface modification method for grafting tetraaniline (TANI), the smallest conjugated repeat unit of polyaniline, onto several materials via perfluorophenylazide photochemistry. The new materials are characterized by nuclear magnetic resonance (NMR) and electrospray ionization (ESI) mass spectroscopy. TANI is shown to be covalently bonded to important carbon materials including graphite, carbon nanotubes (CNTs), and reduced graphene oxide (rGO), as confirmed by transmission electron microscopy (TEM). Furthermore, large area modifications on polyethylene terephthalate (PET) films through dip-coating or spray-coating demonstrate the potential applicability in biomedical applications where high transparency, patternability, and low bio-adhesion are needed. Another important application is preventing biofouling in membranes for water purification. Here we report the first oligoaniline grafted water filtration membranes by modifying commercially available polyethersulfone (PES) ultrafiltration (UF) membranes. The modified membranes are hydrophilic as demonstrated by captive bubble experiments and exhibit extraordinarily low bovine serum albumin (BSA) and Escherichia coli adhesions. Superior membrane performance in terms of flux, BSA rejection and flux recovery after biofouling are demonstrated using a cross-flow system and dead-end cells, showing excellent fouling resistance produced by the in situ modification.

Oligoaniline-based conductive biomaterials for tissue engineering

The science and engineering of biomaterials have improved the human life expectancy. Tissue engineering is one of the nascent strategies with an aim to fulfill this target. Tissue engineering scaffolds are one of the most significant aspects of the recent tissue repair strategies; hence, it is imperative to design biomimetic substrates with suitable features. Conductive substrates can ameliorate the cellular activity through enhancement of cellular signaling. Biocompatible polymers with conductivity can mimic the cells' niche in an appropriate manner. Bioconductive polymers based on aniline oligomers can potentially actualize this purpose because of their unique and tailoring properties. The aniline oligomers can be positioned within the molecular structure of other polymers, thus painter acting with the side groups of the main polymer or acting as a comonomer in their backbone. The conductivity of oligoaniline-based conductive biomaterials can be tailored to mimic the electrical and mechanical properties of targeted tissues/organs. These bioconductive substrates can be designed with high mechanical strength for hard tissues such as the bone and with high elasticity to be used for the cardiac tissue or can be synthesized in the form of injectable hydrogels, particles, and nanofibers for noninvasive implantation; these structures can be used for applications such as drug/gene delivery and extracellular biomimetic structures. It is expected that with progress in the fields of biomaterials and tissue engineering, more innovative constructs will be proposed in the near future. This review discusses the recent advancements in the use of oligoaniline-based conductive biomaterials for tissue engineering and regenerative medicine applications.

STATEMENT OF SIGNIFICANCE

The tissue engineering applications of aniline oligomers and their derivatives have recently attracted an increasing interest due to their electroactive and biodegradable properties. However, no reports have systematically reviewed the critical role of oligoaniline-based conductive biomaterials in tissue engineering. Research on aniline oligomers is growing today opening new scenarios that expand the potential of these biomaterials from "traditional" treatments to a new era of tissue engineering. The conductivity of this class of biomaterials can be tailored similar to that of tissues/organs. To the best of our knowledge, this is the first review article in which such issue is systematically reviewed and critically discussed in the light of the existing literature. Undoubtedly, investigations on the use of oligoaniline-based conductive biomaterials in tissue engineering need further advancement and a lot of critical questions are yet to be answered. In this review, we introduce the salient features, the hurdles that must be overcome, the hopes, and practical constraints for further development.

An addressable packing parameter approach for reversibly tuning the assembly of oligo(aniline)-based supra-amphiphiles

An addressable packing parameter approach was developed for reversibly tuning the self-assembly of oligo(aniline)-based supra-amphiphiles.

We present a newly developed approach to non-covalently address the packing parameter of an electroactive amphiphile. The pH-responsive reversible switching of a tetra(aniline)-based cationic amphiphile, TANI-pentyl trimethylammonium bromide (TANI-PTAB), between self-assembled vesicles and nanowires by acid/base chemistry in aqueous solution is used to exemplify this approach. Trifluoroacetic acid (TFA) was selected as a prototypical acid to form emeraldine salt (ES) state (TANI(TFA)₂-PTAB) vesicles for this new class of small-molecule supramolecular amphiphiles. UV-vis-NIR spectroscopy, transmission electron microscopy (TEM), tapping-mode atomic force microscopy (AFM), and fluorescence spectroscopy were used to investigate the reversible structural transformation from vesicles to nanowires. We show that utilising different protonic acid-dopants for TANI-PTAB can regulate the packing parameter, and thus the final self-assembled structures, in a predictable fashion. We envisage potential application of this concept as smart and switchable delivery systems.

Biocompatible Electroactive Tetra(aniline)-Conjugated Peptide Nanofibers for Neural Differentiation

Peripheral nerve injuries cause devastating problems for the quality of patients' lives, and regeneration following damage to the peripheral nervous system is limited depending on the degree of the damage. Use of nanobiomaterials can provide therapeutic approaches for the treatment of peripheral nerve injuries. Electroactive biomaterials, in particular, can provide a promising cure for the regeneration of nerve defects. Here, a supramolecular electroactive nanosystem with tetra(aniline) (TA)-containing peptide nanofibers was developed and utilized for nerve regeneration. Self-assembled TA-conjugated peptide nanofibers demonstrated electroactive behavior. The electroactive self-assembled peptide nanofibers formed a well-defined three-dimensional nanofiber network mimicking the extracellular matrix of the neuronal cells. Neurite outgrowth was improved on the electroactive TA nanofiber gels. The neural differentiation of PC-12 cells was more advanced on electroactive peptide nanofiber gels, and these biomaterials are promising for further use in therapeutic neural regeneration applications.

Multiple Stimuli-Responsive Fluorescence Behavior of Novel Polyamic Acid Bearing Oligoaniline, Triphenylamine, and Fluorene Groups

Multiple stimuli-responsive fluorescent materials have gained increasing attention for their fundamental investigation and intelligent applications. In this work, we report design and synthesis of a novel polyamic acid bearing oligoaniline, triphenylamine, and fluorene groups, which served as sensitive units and fluorescence emission unit, respectively. The resulting polymer exhibits multiple stimuli-responsive fluorescence switching behavior triggered by redox species, pH, electrochemical, and pressure stimuli. Every fluorescence switching mechanism upon each stimulus was studied in detail. The interactions and energy transfer between sensitive units and emission unit are largely responsible for this fascinating fluorescent switching behavior. This work provides a deep understanding of the optical switching essence upon these stimuli, opening the way for the development of new fluorescent sensing applications.

Solvent Effects on the Structure-Property Relationship of Redox-Active Self-Assembled Nanoparticle-Polyelectrolyte-Surfactant Composite Thin Films: Implications for the Generation of Bioelectrocatalytic Signals in Enzyme-Containing Assemblies

The search for strategies to improve the performance of bioelectrochemical platforms based on supramolecular materials has received increasing attention within the materials science community, where the main objective is to develop low-cost and flexible routes using self-assembly as a key enabling process. Important contributions to the performance of such bioelectrochemical devices have been made based on the integration and supramolecular organization of redox-active polyelectrolyte-surfactant complexes on electrode supports. Here, we examine the influence of the processing solvent on the interplay between the supramolecular mesoorganization and the bioelectrochemical properties of redox-active self-assembled nanoparticle-polyelectrolyte-surfactant nanocomposite thin films. Our studies reveal that the solvent used in processing the supramolecular films and the presence of metal nanoparticles not only have a substantial influence in determining the mesoscale organization and morphological characteristics of the film but also have a strong influence on the efficiency and performance of the bioelectrochemical system. In particular, a higher bioelectrochemical response is observed when nanocomposite supramolecular films were cast from aqueous solutions. These observations seem to be associated with the fact that the use of aqueous solvents increases the hydrophilicity of the film, thus favoring the access of glucose, particularly at low concentrations. We believe that these results improve our current understanding of supramolecular nanocomposite materials generated via polyelectrolyte-surfactant complexes, in order to use the processing conditions as a variable to improve the performance of bioelectrochemical devices.

3D Printing of Aniline Tetramer-Grafted-Polyethylenimine and Pluronic F127 Composites for Electroactive Scaffolds

Electroactive hydrogel scaffolds are fabricated by the 3D-printing technique using composites of 30% Pluronic F127 and aniline tetramer-grafted-polyethylenimine (AT-PEI) copolymers with various contents from 2.5% to 10%. The synthesized AT-PEI copolymers can self-assemble into nanoparticles with the diameter of ≈50 nm and display excellent electroactivity due to AT conjugation. The copolymers are then homogeneously distributed into 30% Pluronic F127 solution by virtue of the thermosensitivity of F127, denoted as F/AT-PEI composites. Macroscopic photographs of latticed scaffolds elucidate their excellent printability of F/AT-PEI hydrogels for the 3D-printing technique. The conductivities of the printed F/AT-PEI scaffolds are all higher than 2.0 × 10^-3 S cm^-1 , which are significantly improved compared with that of F127 scaffold with only 0.94 × 10^-3 S cm^-1 . Thus, the F/AT-PEI scaffolds can be considered as candidates for application in electrical stimulation of tissue regeneration such as repair of muscle and cardiac nerve tissue.

Exploring Redox States, Doping and Ordering of Electroactive Star-Shaped Oligo(aniline)s

We have prepared a simple star-shaped oligo(aniline) (TDPB) and characterised it in detail by MALDI-TOF MS, UV/Vis/NIR spectroscopy, time-dependent DFT, cyclic voltammetry and EPR spectroscopy. TDPB is part of an underdeveloped class of π-conjugated molecules with great potential for organic electronics, display and sensor applications. It is redox active and reacts with acids to form radical cations. Acid-doped TDPB shows behaviour similar to discotic liquid crystals, with X-ray scattering investigations revealing columnar self-assembled arrays. The combination of unpaired electrons and supramolecular stacking suggests that star-shaped oligo(aniline)s like TDPB have the potential to form conducting nanowires and organic magnetic materials.

Influence of solvent polarity on the structure of drop-cast electroactive tetra(aniline)-surfactant thin films

The structure of drop-cast thin films of an electroactive oligomer–surfactant complex can be tuned through variation of solvent polarity.

Branch-Selective Alkene Hydroarylation by Cooperative Destabilization: Iridium-Catalyzed ortho-Alkylation of Acetanilides

An iridium(I) catalyst system, modified with the wide-bite-angle and electron-deficient bisphosphine d(F) ppb (1,4-bis(di(pentafluorophenyl)phosphino)butane) promotes highly branch-selective hydroarylation reactions between diverse acetanilides and aryl- or alkyl-substituted alkenes. This provides direct and ortho-selective access to synthetically challenging anilines, and addresses long-standing issues associated with related Friedel-Crafts alkylations.

Self-Assembly of a Functional Oligo(Aniline)-Based Amphiphile into Helical Conductive Nanowires

A tetra(aniline)-based cationic amphiphile, TANI-NHC(O)C5H10N(CH3)3(+)Br(-) (TANI-PTAB) was synthesized, and its emeraldine base (EB) state was found to self-assemble into nanowires in aqueous solution. The observed self-assembly is described by an isodesmic model, as shown by temperature-dependent UV-vis investigations. Linear dichroism (LD) studies, combined with computational modeling using time-dependent density functional theory (TD-DFT), suggests that TANI-PTAB molecules are ordered in an antiparallel arrangement within nanowires, with the long axis of TANI-PTAB arranged perpendicular to the nanowire long axis. Addition of either S- or R- camphorsulfonic acid (CSA) to TANI-PTAB converted TANI to the emeraldine salt (ES), which retained the ability to form nanowires. Acid doping of TANI-PTAB had a profound effect on the nanowire morphology, as the CSA counterions' chirality translated into helical twisting of the nanowires, as observed by circular dichroism (CD). Finally, the electrical conductivity of CSA-doped helical nanowire thin films processed from aqueous solution was 2.7 mS cm(-1). The conductivity, control over self-assembled 1D structure and water-solubility demonstrate these materials' promise as processable and addressable functional materials for molecular electronics, redox-controlled materials and sensing.