Coatable Negative Dispersion Retarder: Kinetically Controlled Self-Assembly Pathway of Butterfly-Shaped Molecular Building Blocks for the Construction of Nanocolumns.

Disc-shaped building blocks with columnar phases have attracted attention for their potential in optical applications, including a retarder. However, to achieve coatable high-performance optical films, it is essential to understand a subtle interaction balance between building blocks and relevant self-assembled behaviors during material processing. Herein, we studied a self-assembled nanocolumn evaluation of linear butterfly-shaped dendrons (T-AD) consisting of thiophene-based conjugated core and flexible alkyl dendron.

Long-wave infrared transparent sulfur polymers enabled by symmetric thiol cross-linker.

Infrared (IR) transmissive polymeric materials for optical elements require a balance between their optical properties, including refractive index (n) and IR transparency, and thermal properties such as glass transition temperature (T). Achieving both a high refractive index (n) and IR transparency in polymer materials is a very difficult challenge. In particular, there are significant complexities and considerations to obtaining organic materials that transmit in the long-wave infrared (LWIR) region, because of high optical losses due to the IR absorption of the organic molecules.

Effects on the Thermo-Mechanical and Interfacial Performance of Newly Developed PI-Sized Carbon Fiber-Polyether Ether Ketone Composites: Experiments and Molecular Dynamics Simulations.

In this study, polyether ether ketone (PEEK) composites reinforced with newly developed water-dispersible polyimide (PI)-sized carbon fibers (CFs) were developed to enhance the effects of the interfacial interaction between PI-sized CFs and a PEEK polymer on their thermo-mechanical properties. The PI sizing layers on these CFs may be induced to interact vigorously with the p-phenylene groups of PEEK polymer chains because of increased electron affinity. Therefore, these PI-sized CFs are effective for improving the interfacial adhesion of PEEK composites.

Structural Effect of Polyimide Precursors on Highly Thermally Conductive Graphite Films.

In this study, polyimide (PI) with high carbonization yield was used as a precursor to prepare graphite films with high thermal conductivity. The crystallinity, grain size, and thermal conductivity of the graphite films were characterized and found to vary according to the chemical structure of the PI precursor. Aromatic PIs containing ortho-substituted hydroxyl groups in the PI main chain (DHB-BPDA) were synthesized by the polycondensation reaction of 3,3'-dihydroxybenzidine (DHB) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).

Ultrahigh strength, modulus, and conductivity of graphitic fibers by macromolecular coalescence.

Theoretical considerations suggest that the strength of carbon nanotube (CNT) fibers be exceptional; however, their mechanical performance values are much lower than the theoretical values. To achieve macroscopic fibers with ultrahigh performance, we developed a method to form multidimensional nanostructures by coalescence of individual nanotubes. The highly aligned wet-spun fibers of single- or double-walled nanotube bundles were graphitized to induce nanotube collapse and multi-inner walled structures.

Surface Modification of Sulfur-Assisted Reduced Graphene Oxide with Poly(phenylene sulfide) for Multifunctional Nanocomposites.

The sulfur on the sulfur-assisted reduced graphene oxide (SrGO) surface provides the origin of poly(phenylene sulfide) PPS-grafting via SAr mechanism. In-situ polymerization from sulfur on SrGO afforded surface modification of SrGO, resulting in enhanced dispersibility in PPS. The tensile strength, electrical and thermal conductivities, and flame retardancy of PPS-coated SrGO were efficiently enhanced using highly concentrated SrGO and masterbatch (MB) for industrial purposes.

Tunable Synthesis of Predominant Semi-Ionic and Covalent Fluorine Bonding States on a Graphene Surface.

In this study, fluorinated graphene (FG) was synthesized via a hydrothermal reaction. Graphene oxides (GOs) with different oxygen bonding states and oxygen contents (GO(F), GO(P), and GO(HU)) were used as starting materials. GO(F) and GO(P) are commercial-type GOs from Grapheneall.

Analysis of the effect of organic solvent-sheet interfacial interaction on the exfoliation of sulfur-doped reduced graphene oxide sheets in a solvent system using molecular dynamics simulations.

In this study, the effect of interfacial interaction between solvent and sheets on the exfoliation of sulfur-doped reduced graphene oxide (SrGO) sheets was studied, using molecular dynamics simulations. Four organic solvents of toluene, tetrahydrofuran, N-methyl-2-pyrrolidone, and sulfolane, were used in this simulation. An insertion simulation considering the size effect of insertion molecules was used to determine the insertion efficiency of the solvent molecules.

Fast chemical recycling of carbon fiber reinforced plastic at ambient pressure using an aqueous solvent accelerated by a surfactant.

The properties of infusibility and insolubility in organic solvent of cured epoxy resin makes it difficult to recycle carbon fiber reinforced plastics (CFRP). We have reported the recycling of CFRPs using the oxidizing power of hydroxyl radicals generated from NaOCl solution. In our study, we used benzyltrimethylammonium bromide (BTAB) and sodium dodecyl sulfate (SDS) for the interfacial separation between the epoxy resin and carbon fibers (CF).

Molecular Design and Property Prediction of Sterically Confined Polyimides for Thermally Stable and Transparent Materials.

To meet the demand for next-generation flexible optoelectronic devices, it is crucial to accurately establish the chemical structure-property relationships of new optical polymer films from a theoretical point of view, prior to production. In the current study, computer-aided simulations of newly designed poly(ester imide)s (PEsIs) with various side groups (⁻H, ⁻CH₃, and ⁻CF₃) and substituted positions were employed to study substituent-derived steric effects on their optical and thermal properties. From calculations of the dihedral angle distribution of the model compounds, it was found that the torsion angle of the C⁻N imide bonds was effectively constrained by the judicious introduction of di-, tetra-, and hexa-substituted aromatic diamines with ⁻CF₃ groups.

Facile in Situ Synthesis of Multiple-Heteroatom-Doped Carbons Derived from Polyimide Precursors for Flexible All-Solid-State Supercapacitors.

Efficient strategies to prepare carbon materials with improved electrochemical performance for supercapacitors have been in great demand. Herein, we develop multiple-heteroatom-doped carbons (from single- to triple-doped) by pyrolysis of polyimide precursors using a facile in situ approach. This approach can be used to tune heteroatom compositions by controlling the desired polyimide monomer functional groups as well as introducing external doping sources into the polyimide precursor solutions.

Influences of carboxyl functionalization of intercalators on exfoliation of graphite oxide: a molecular dynamics simulation.

In this study, the influences of the carboxyl functionalization of intercalators on exfoliation of graphite oxide were analyzed using molecular dynamics (MD) simulations. Molecular models of four-layered graphene oxide (GO) sheets, four different solvents (ethanol, dimethylformamide, tetrahydrofuran, and N-methyl-2-pyrrolidone), and four different intercalators (anthracene, 2-anthracenecarboxylic acid, 2,3-anthracenedicarboxylic acid, and 2,6-anthracenedicarboxylic acid) were used in the MD simulations. A separation simulation of GO sheets was performed to determine the point at which the GO sheets begin to exfoliate.

Hollow polymer microcapsule embedded transparent and heat-insulating film.

We herein report a facile and scalable approach to manufacturing optically transparent and heat-insulating films by incorporating hollow poly(methyl methacrylate) microcapsules into a transparent polymeric matrix. The microcapsule was prepared emulsion polymerization. The size of the microcapsules could be easily controlled from ∼1 to 3 μm by varying the polymerization time in a narrow size distribution.

Additive-free hollow-structured Co3O4 nanoparticle Li-ion battery: the origins of irreversible capacity loss.

Origins of the irreversible capacity loss were addressed through probing changes in the electronic and structural properties of hollow-structured Co3O4 nanoparticles (NPs) during lithiation and delithiation using electrochemical Co3O4 transistor devices that function as a Co3O4 Li-ion battery. Additive-free Co3O4 NPs were assembled into a Li-ion battery, allowing us to isolate and explore the effects of the Co and Li2O formation/decomposition conversion reactions on the electrical and structural degradation within Co3O4 NP films. NP films ranging between a single monolayer and multilayered film hundreds of nanometers thick prepared with blade-coating and electrophoretic deposition methods, respectively, were embedded in the transistor devices for in situ conduction measurements as a function of battery cycles.

Simultaneous study of exciton diffusion/dissociation and charge transport in a donor-acceptor bilayer: pentacene on a C60 -terminated self-assembled monolayer.

In-situ photoinduced threshold voltage measurement is a sensitive probe for exploring charge transport and exciton diffusion simultaneously, the main determinants of the power conversion efficiency in organic photovoltaic devices. The exciton diffusion length in a pentacene film deposited onto a C60 -terminated self-assembled monolayer is measured. The methodology and analysis presented here can be applied in the design and engineering of electron/donor acceptor interfaces for photovoltaic devices.

Chemical method for improving both the electrical conductivity and mechanical properties of carbon nanotube yarn via intramolecular cross-dehydrogenative coupling.

Chemical post-treatment of the carbon nanotube fiber (CNTF) was carried out via intramolecular cross-dehydrogenative coupling (ICDC) with FeCl3 at room temperature. The Raman intensity ratio of the G band to the D band (IG/ID ratio) of CNT fiber increased from 2.3 to 4.