Morphology-Retaining Carbonization of Honeycomb-Patterned Hyperbranched Poly(phenylene vinylene) Film

Ordered porous materials are of great technological interest for use as separation, catalysis, adsorbents, and electronic devices. We report here a fabrication of honeycomb-patterned porous films from fluorescent hyperbranched poly(phenylene vinylene) (hypPPV) by breath figure method and the thermal conversion of this film to macroporous carbon. This hexagonal porous film is very thermally stable and retained its structure at up to >600 °C. After the heating, carbonization of hypPPV occurred, and black porous carbon film was obtained. Additionally, because π-conjugated hypPPV has many vinylene moieties at its terminus, the photo-cross-linking reaction easily proceeds without the collapse of the honeycomb structures. This cross-linking reaction rendered the honeycomb films completely insoluble in organic solvents. Because of the provided high thermal and chemical stability, the honeycomb films are a new class of microstructured materials that is promising for many applications such as durable electroluminescence devices, bandgap materials, adsorbents, electrodes, and solvent-resistant porous membranes

Antioxidant and Adsorption Properties of Bioinspired Phenolic Polymers: A Comparative Study of Catechol and Gallol

Polyphenols, which by the Quideau definition are plant-derived chemicals with two or more phenolic groups, have attracted interest because of their antioxidant activity, adsorption on universal substrates, and biocompatibility. Most polyphenols include gallol groups in their chemical structures, which has inspired us to synthesize gallol-functionalized polymers. We report the reversible addition–fragmentation chain transfer polymerization of 3,4,5-trimethoxystyrene using cyanomethyl dodecyl trithiocarbonate as the chain transfer agent. This method produces well-defined polymers with a wide range of molecular weight (from 5.4 to 53.4 kg mol^–1) and low polydispersity index (<i>M</i>_w/<i>M</i>_n < 1.3). Subsequent demethylation of poly­(3,4,5-trimethoxystyrene) (PTMS) yields poly­(3,4,5-trihydroxystyrene) (polyvinylgallol, PVGal). These newly synthesized polymers exhibit greater antioxidant activities than widely used catechol-functionalized polymers based on the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), 2,2′-azinobis­(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and oxygen radical absorbance capacity (ORAC) methods. Also, PVGal showed better adsorption properties on metals and SiO₂ substrates than those of the other phenolic polymers. Given these high antioxidant and adsorption properties, the effective use of gallol-funcationalized polymers in biomaterials is expected

Seawater-Assisted Self-Healing of Catechol Polymers via Hydrogen Bonding and Coordination Interactions

It is highly desirable to prevent crack formation in polymeric materials at an early stage and to extend their lifespan, particularly when repairs to these materials would be difficult for humans. Here, we designed and synthesized catechol-functionalized polymers that can self-heal in seawater through hydrogen bonding and coordination. These bioinspired acrylate polymers are originally viscous materials, but after coordination with environmentally safe, common metal cations in seawater, namely, Ca²⁺ and Mg²⁺, the mechanical properties of the polymers were greatly enhanced from viscous to tough, hard materials. Reduced swelling in seawater compared with deionized water owing to the higher osmotic pressure resulted in greater toughness (∼5 MPa) and self-healing efficiencies (∼80%)

Biological Identification of Peptides that Specifically Bind to Poly(phenylene vinylene) Surfaces: Recognition of the Branched or Linear Structure of the Conjugated Polymer

Peptides that bind to poly(phenylene vinylene) (PPV) were identified by the phage display method. Aromatic amino acids were enriched in these peptide sequences, suggesting that a π−π interaction is the key interaction between the peptides and PPV. The surface plasmon resonance (SPR) experiments using chemically synthesized peptides demonstrated that the Hyp01 peptide, with the sequence His-Thr-Asp-Trp-Arg-Leu-Gly-Thr-Trp-His-His-Ser, showed an affinity constant (7.7 × 105 M−1) for the target, hyperbranched PPV (hypPPV) film. This value is 15-fold greater than its affinity for linear PPV (linPPV). In contrast, the peptide screened for linPPV (Lin01) showed the reverse specificity for linPPV. These results suggested that the Hyp01 and Lin01 peptides selectively recognized the linear or branched structure of PPVs. The Ala-scanning experiment, circular dichroism (CD) spectrometry, and molecular modeling of the Hyp01 peptide indicated that adequate location of two Trp residues by forming the polyproline type II (PII) helical conformation allowed the peptide to specifically interact with hypPPV

Synthesis of Dithiocatechol-Pendant Polymers

Although the synthesis of thiophenol-pendant polymers was reported in the 1950s, the polymers generally suffered from oxidation and became insoluble in organic solvents, hampering detailed characterization and further applications. Dithiocatechol-pendant polymers, which have one additional ortho-thiol group than thiophenol-pendant polymers, have never been synthesized, despite their promise in various applications due to their analogous molecular structure with catechol-pendant polymers. Herein, we report the first synthesis of dithiocatechol-pendant polymers using a novel protection–deprotection strategy. We carefully examined the synthetic routes and identified the deprotection conditions that do not cause cross-linking of the dithiocatechol moieties. Because the resulting dithiocatechol-pendant polymers were soluble in common organic solvents (e.g., tetrahydrofuran and N,N-dimethylformamide), the polymers can be fully characterized by standard spectroscopic methods, providing valuable data for future researchers. We also showed that besides free-radical polymerization, reversible addition–fragmentation chain-transfer polymerization can also be adopted to synthesize dithiocatechol-pendant polymers. This work paves the way for the exploitation of dithiocatechol-containing polymers for the fabrication of novel functional materials

Molecular Dynamics Simulation of Adhesion of Additive Molecules in Paint Materials toward Enhancement of Anticorrosion Performance

Adsorption energies of additive molecules in paint materials on the iron oxide substrate are investigated by molecular dynamics (MD) simulations to find the key feature of adhesion, which is one of the indispensable elements for the corrosion resistance of coated materials. Both edge-on and face-on adsorptions are observed for most additive molecules such as phenylsuccinic acid and benzoic acid. On the other hand, only the edge-on adsorption is observed for the specific molecule having a benzothiazole ring due to the effect of steric conformation. The largest adsorption energy per functional group is observed for two nitrogen atoms in the thiazole ring and amino group, which influences the relationship between face-on and edge-on adsorption energies. Moreover, a correlation analysis using RDKit descriptors is performed to discuss the dominant factor for the adsorption energy of additive molecules. The descriptor for the magnitude of partial charge relative to the molecular surface area and the one for the topological polar surface area have the largest correlation with the adsorption energy of the target molecules. It is significant in this study to extract key factors that contribute to molecular adhesion through MD simulations in combination with correlation analysis using RDKit descriptors. This study is a good example of the computer-assisted design of new paint materials

Exploring Caffeic Acid and Lignosulfonate as Key Phenolic Ligands for Metal-Phenolic Network Assembly

Films formed by metals and phenols through a coordinative interaction have been extensively studied in previous years. We report the successful formation of MPN films from the phenolic compounds caffeic acid and lignosulfonate using Fe3+ ions for complexation. The likewise examined p-coumaryl alcohol showed some MPN film formation tendency, while for coniferyl alcohol and sinapyl alcohol, no successful film buildup could be observed. These newly formed films were compared to tannic acid-Fe3+ films as a reference. Film growth and degradation were tracked by using UV–vis absorption spectroscopy. The films were degradable under different conditions such as alkaline environments or in the presence of a strong chelator. Small hollow capsules with a diameter of 3 μm and thicknesses in the nanometer range were produced. Additionally, the prepared films showed varying colors and levels of wettability. By utilizing the films’ coating properties, we successfully dyed human hair in various colors

Peptide-Based Switching of Polymer Fluorescence in Aqueous phase

Peptide-Based Switching of Polymer Fluorescence in Aqueous phas

Coordination-Driven Multistep Assembly of Metal–Polyphenol Films and Capsules

We report the assembly of metal-polyphenol complex (MPC) films and capsules through the sequential deposition of iron­(III) ions (Fe^(III)) and a natural polyphenol, tannic acid (TA), driven by metal–ligand coordination. Stable Fe^(III)/TA films and capsules were formed, indicating lateral and longitudinal cross-linking of TA by Fe^(III) in the film structure. Quartz crystal microbalance, ultraviolet–visible (UV-vis) spectrophotometry, and X-ray photoelectron spectroscopy were carried out to quantitatively analyze the film growth. A comparison of the MPC capsules prepared through multistep assembly with those obtained through one-step deposition, as reported previously [Ejima et al., <i>Science</i> <b>2013</b>, <i>341</i>, 154–156], reveals substantial differences in the nature of complexation and in their physicochemical properties, including permeability, stiffness, and degradability. This study highlights the importance of engineering MPC films with different properties through implementing different assembly methods

Engineering Cellular Degradation of Multilayered Capsules through Controlled Cross-Linking

We report a versatile approach for controlling the intracellular degradation of polymer capsules by tailoring the degree of cross-linking in the capsules. Poly(2-diisopropylaminoethyl methacrylate) capsules were assembled by the layer-by-layer technique and covalently stabilized with a redox-responsive bisazide cross-linker using click chemistry. The degree of cross-linking, determined using radiation scintillation counting, was tuned from 65% to 98% by adjusting the amount of cross-linker used to stabilize the polymer films. Transmission electron microscopy and fluorescence microscopy studies showed that the pH responsiveness of the capsules was maintained, regardless of the degree of cross-linking. Atomic force microscopy measurements on planar surfaces revealed that increasing the degree of cross-linking decreased the film roughness (from 8.7 to 1.7 nm), hence forming smoother films; however the film thicknesses were not significantly altered. Cellular studies showed that the rate of intracellular degradation of the capsules could be controlled between 0 and 6 h by altering the degree of cross-linking in the polymer capsules. These studies also demonstrated that the cellular degradation of highly cross-linked capsules (>90%) was significantly retarded compared to degradation in simulated cellular conditions. This suggests that the naturally occurring cellular reducing environment is rapidly depleted, and there is a significant delay before the cells can replenish the reducing environment. The modular and versatile nature of this approach lends itself to application to a wide range of polymer carriers and thus offers significant potential for the design of polymer-based systems for drug and gene delivery