Effects of Substituent on Binaphthyl Hinge-Containing Conductive Polymers

Conductive polymers containing hinged 1,1′-binaphthyl were synthesized. Their conformational flexibility around the 1,1′ C–C bonds was found to vary with the substituents at the 2,2′-positionshydroxy, linear alkyloxy, and macrocyclic alkyloxy groups were compared. Macrocyclic alkyloxy groups appeared to immobilize the binaphthyl. The connection patterns of electroactive oligothiophenes to the binaphthyl groups were also investigated with 6,6′- and 7,7′-attachments. The substituents binaphthyl polymers were examined using cyclic voltammetry, <i>in situ</i> conductivity measurements, and spectroelectrochemistry. Their electronic properties were found to vary greatly with the substituents and their connectivity. Binaphthyl polymer with hydroxyls and 3,4-ethylenedioxythiophenes exhibited interesting charge-trapping properties. 7,7′-Substitution led to intrachain interactions, which were promoted by the presence of linear alkyl chains. The observed properties give binaphthyl hinge-containing conductive polymers potential applicability in chiral electroactive sensors, polymer actuators, and electrochromic and optoelectronic devices

Enhancement of Photoinduced Electron Transfer in Self-Assembled Polymer Films Using Mixed Metal–Terpyridine Complexes

The design and synthesis of photoactive polymeric systems are important in regard to solar energy harvesting and utilization. In this report, we synthesized photoactive polymeric thin films via iterative self-assembly using reversible metal–terpyridine (M–tpy) interactions. The growth rate of thin film deposition depends on the metal ion of choice. Ru­(II)­(tpy)₂-incorporated poly­(vinyl alcohol) also functionalized with tpy was subjected to iterative self-assembly on glass substrates. UV–vis spectroscopy and surface profilometer investigations show that the polymeric thin films with Cu­(II) grew 2 times faster than those with Zn­(II), attributed to the strong M–tpy interaction. Interestingly, photocurrent generated in the polymeric thin films with Zn­(II) was much higher than those of other films. The apparent diffusion rate constant (<i>k</i>_app) was measured for the electron hopping process via potential-step chronoamperometry. As a result, the <i>k</i>_app for the polymeric thin films with Zn­(II) was almost 2 times larger than those with other metal ions. The choice of metal ions appears crucial in the mixed metal–tpy complex systems not only for the film growth but also for the efficient photoinduced electron transfer

Copper-Catalyzed Aza-Michael Addition of 2‑Aminobenzoate to β‑Substituted α,β-Unsaturated Ketones: One-Pot Synthesis of 3‑Carbonyl-2-Substituted Quinolin-4(1<i>H</i>)‑ones

We present a new and straightforward one-pot process for the synthesis of 3-carbonyl-4-quinolone derivatives through highly efficient Cu-catalyzed aza-Michael addition of 2-aminobenzoates to β-substituted α,β-unsaturated ketones/cyclization/mild oxidation reactions. A broad range of new versatile 3-carbonyl-quinolin-4­(1<i>H</i>)-ones is prepared from readily available chemicals under mild reaction conditions with short reaction times, producing good to excellent yields (up to 99%)

<i>N</i>‑Heterocyclic Carbene-Based Conducting Polymer–Gold Nanoparticle Hybrids and Their Catalytic Application

Hybrid nanocomposites of <i>N</i>-heterocyclic carbene (NHC)-functionalized conducting polymers (CPs) with gold nanoparticles (AuNPs) were prepared by concurrent disproportionation and oxidative coupling. The formation of hybrid nanocomposites, NHC-CP/AuNPs, in the simultaneous process was confirmed by transmission electron microscopy, powder X-ray diffraction, cyclic voltammetry, and ¹³C solid-state NMR analyses. More importantly, the NHC group played a pivotal role in the dispersion of AuNPs. Further, NHC-CP/AuNPs exhibited good catalytic activity for the reduction of 4-nitrophenol

Torsionally Responsive Tropone-Fused Conjugated Polymers

Torsionally responsive molecular systems can change their electronic properties according to the dihedral angles and can be utilized as sensory materials. We have designed and synthesized novel tropone-fused conjugated polymers <b>PBTr</b>, <b>PBTr-T</b>, and <b>PBTr-Tz</b> that showed interesting dihedral-angle-dependent variations in UV–vis absorptions. Tropone-fused thiophene derivatives were prepared from one-step condensation of thiophene-3,4-dialdehyde and aliphatic ketones via a modular, facile, and high-yielding method. Subsequent halogenation and Stille cross-coupling polymerization with a bis­(stannyl)­benzo­dithiophene resulted in a tropone-fused conjugated polymer <b>PBTr</b>. We were also able to prepare thiophene- and thiazole-bridged polymers, <b>PBTr-T</b> and <b>PBTr-Tz</b>, respectively, using similar synthetic methods. Electronic absorptions of the newly synthesized <b>PBTrs</b> were measured in solutions and in films states. Substantial red-shifts occurred in the case of thiophene-bridged <b>PBTr-T</b>, whereas almost no shift was observed for thiazole-bridged <b>PBTr-Tz</b>. We attributed this to the substantial change in the torsional angle between the tropone-fused thiophene moiety and thiophene, which was further supported by density functional theory (DFT) calculations. Similar spectral changes of UV–vis absorptions were observed when a poor solvent (methanol) was introduced to a chloroform solution of <b>PBTr-T</b>. Reverse torsional angle variations were realized with initially planar <b>PBTr-Tz</b> by introducing steric hindrance through protonation on the thiazole rings. We believe that torsionally responsive tropone-fused conjugated polymers are promising as novel platforms for sensory applications

Structural Effect of Thioureas on the Detection of Chemical Warfare Agent Simulants

The ability to rapidly detect, identify, and monitor chemical warfare agents (CWAs) is imperative for both military and civilian defense. Since most CWAs and their simulants have an organophosphonate group, which is a hydrogen (H)-bond acceptor, many H-bond donors have been developed to effectively bind to the organophosphonate group. Although thioureas have been actively studied as an organocatalyst, they are relatively less investigated in CWA detection. In addition, there is a lack of studies on the structure–property relationship for gas phase detection. In this study, we synthesized various thioureas of different chemical structures, and tested them for sensing dimethylmethylphosphonate (DMMP), a CWA simulant. Molecular interaction between DMMP and thiourea was measured by ¹H NMR titration and supported by density functional theory (DFT) calculations. Strong H-bond donor ability of thiourea may cause self-aggregation, and CH−π interaction can play an important role in the DMMP detection. Gas-phase adsorption of DMMP was also measured using a quartz crystal microbalance (QCM) and analyzed using the simple Langmuir isotherm, showing the importance of structure-induced morphology of thioureas on the surface

Three-Dimensional Electroconductive Hyaluronic Acid Hydrogels Incorporated with Carbon Nanotubes and Polypyrrole by Catechol-Mediated Dispersion Enhance Neurogenesis of Human Neural Stem Cells

Electrically conductive hyaluronic acid (HA) hydrogels incorporated with single-walled carbon nanotubes (CNTs) and/or polypyrrole (PPy) were developed to promote differentiation of human neural stem/progenitor cells (hNSPCs). The CNT and PPy nanocomposites, which do not easily disperse in aqueous phases, dispersed well and were efficiently incorporated into catechol-functionalized HA (HA–CA) hydrogels by the oxidative catechol chemistry used for hydrogel cross-linking. The prepared electroconductive HA hydrogels provided dynamic, electrically conductive three-dimensional (3D) extracellular matrix environments that were biocompatible with hNSPCs. The HA–CA hydrogels containing CNT and/or PPy significantly promoted neuronal differentiation of human fetal neural stem cells (hfNSCs) and human induced pluripotent stem cell-derived neural progenitor cells (hiPSC-NPCs) with improved electrophysiological functionality when compared to differentiation of these cells in a bare HA–CA hydrogel without electroconductive motifs. Calcium channel expression was upregulated, depolarization was activated, and intracellular calcium influx was increased in hNSPCs that were differentiated in 3D electroconductive HA–CA hydrogels; these data suggest a potential mechanism for stem cell neurogenesis. Overall, our bioinspired, electroconductive HA hydrogels provide a promising cell-culture platform and tissue-engineering scaffold to improve neuronal regeneration

Chemically Driven, Water-Soluble Composites of Carbon Nanotubes and Silver Nanoparticles as Stretchable Conductors

In the past decade, hybrid materials for highly stretchable, conductive electrodes have received tremendous attention in the fields of emerging wearable electronic, optoelectronic, and sensing devices. Here, we present a previously unrecognized aqueous route to producing stretchable conductors composed of silver nanoparticles (AgNPs) and single-walled carbon nanotubes (SWNTs) embedded in a polyurethane (PU) matrix, in contrast to ones dispersed in toxic organic solvents reported to date. The intact chemical interaction between one-dimensional SWNTs, for endowing the capability of establishing conductive pathways even in stretching conditions, and AgNPs, for enabling high conductivity of the composites, is achieved in an aqueous medium with an anionic polyelectrolyte, poly­(acrylic acid), that undergoes pH-dependent conformational evolution. With this aqueous approach, we demonstrate that AgNP–SWNT–PU composites supported on PDMS substrates have the conductivities of 620 and 120 S cm^–1 in unstrained and 90% elongated conditions, respectively, and display repeatable reversibility at a strain of 60%

Role of Adsorbed Surfactant in the Reaction of Aryl Diazonium Salts with Single-Walled Carbon Nanotubes

Because covalent chemistry can diminish the optical and electronic properties of single-walled carbon nanotubes (SWCNTs), there is significant interest in developing methods of controllably functionalizing the nanotube sidewall. To date, most attempts at obtaining such control have focused on reaction stoichiometry or strength of oxidative treatment. Here, we examine the role of surfactants in the chemical modification of single-walled carbon nanotubes with aryl diazonium salts. The adsorbed surfactant layer is shown to affect the diazonium derivatization of carbon nanotubes in several ways, including electrostatic attraction or repulsion, steric exclusion, and direct chemical modification of the diazonium reactant. Electrostatic effects are most pronounced in the cases of anionic sodium dodecyl sulfate and cationic cetyltrimethylammonium bromide, where differences in surfactant charge can significantly affect the ability of the diazonium ion to access the SWCNT surface. For bile salt surfactants, with the exception of sodium cholate, we find that the surfactant wraps tightly enough such that exclusion effects are dominant. Here, sodium taurocholate exhibits almost no reactivity under the explored reaction conditions, while for sodium deoxycholate and sodium taurodeoxycholate, we show that the greatest extent of reaction is observed among a small population of nanotube species, with diameters between 0.88 and 0.92 nm. The anomalous reaction of nanotubes in this diameter range seems to imply that the surfactant is less effective at coating these species, resulting in a reduced surface coverage on the nanotube. Contrary to the other bile salts studied, sodium cholate enables high selectivity toward metallic species and small band gap semiconductors, which is attributed to surfactant-diazonium coupling to form highly reactive diazoesters. Further, it is found that the rigidity of anionic surfactants can significantly influence the ability of the surfactant layer to stabilize the diazonium ion near the nanotube surface. Such Coulombic and surfactant packing effects offer promise toward employing surfactants to controllably functionalize carbon nanotubes

Long dsRNA-Mediated RNA Interference and Immunostimulation: A Targeted Delivery Approach Using Polyethyleneimine Based Nano-Carriers

RNA oligonucleotides capable of inducing controlled immunostimulation combined with specific oncogene silencing via an RNA interference (RNAi) mechanism provide synergistic inhibition of cancer cell growth. With this concept, we previously designed a potent immunostimulatory long double stranded RNA, referred to as liRNA, capable of executing RNAi mediated specific target gene silencing. In this study, we developed a highly effective liRNA based targeted delivery system to apply in the treatment of glioblastoma multiforme. A stable nanocomplex was fabricated by complexing multimerized liRNA structures with cross-linked branched poly­(ethylene imine) (bPEI) via electrostatic interactions. We show clear evidence that the cross-linked bPEI was quite effective in enhancing the cellular uptake of liRNA on U87MG cells. Moreover, the liRNA-PEI nanocomplex provided strong RNAi mediated target gene silencing compared to that of the conventional siRNA-PEI complex. Further, the bPEI modification strategy with specific ligand attachment assisted the uptake of the liRNA-PEI complex on the mouse brain endothelial cell line (b.End3). Such delivery systems combining the beneficial elements of targeted delivery, controlled immunostimulation, and RNAi mediated target silencing have immense potential in anticancer therapy