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The surface of carbon fibers (CFs) is often modified by multi-walled carbon nanotubes (MWCNTs), and the effect of the interface on the mechanical properties has been reported mostly for epoxy matrices. We achieved effective surface modification of CFs by a simple two-step process to graft a large amount of MWCNTs using a highly reactive polymer to enhance the bonding between CFs and MWCNTs. The first step was the reactive mono-molecular coating of a reactive polymer (poly-2-isopropenyl-2-oxazoline; Pipozo) that has high reactivity with COOH from CFs and MWCNTs. The high reactivity between the oxazoline group and COOH or phenol OH was confirmed for low-molecular-weight reactions. The second step was the coating of MWCNTs from a dispersion in a solvent. This simple process resulted in a substantial amount of MWCNTs strongly bonded to CF, even after washing. The MWCNTs grafted onto CFs remained even after melt-mixing. The effect on the interface, i.e., physical anchoring, led to an improvement of the mechanical properties. The novelty of the present study is that Pipozo acted as a molecular bonding layer between CFs and MWCNTs as a physical anchoring structure formed by a simple process, and the interface caused a 20% improvement in the tensile strength and modulus. This concept of a composite having a physical anchoring structure of MWCNTs on CFs has potential applications for lightweight thermoplastics, such as in the automotive industry.

Polystyrene (PS) has low impact strength and also shows poor strain hardening. In this work, poly(styrene–butadiene–styrene) triblock copolymer (SBS) was solution- and melt-blended with PS in the presence of a free-radical polymerization initiator, dicumyl peroxide (DCP), to enhance PS’s thermal stability, mechanical properties, impact resistance, and strain hardening. The solution-blended PS/SBS containing 0.1% DCP annealed at 180 °C showed strong strain hardening, but the melt-blended PS/SBS annealed at the same temperature and time showed poor strain hardening. The change in the blending temperature, DCP concentration, and PS-to-SBS ratio had minimal effect on the strain hardening of melt-blended PS/SBS. The tensile strength increased with an increase in the concentration of DCP up to 0.1%, and beyond that level, the tensile strength started decreasing. The impact resistance considerably improved with an increase in the SBS loading in the PS matrix, and the enhancement was more than double of the impact resistance shown by the neat PS.

The effect of a long alkyl end group on the thermal and structural properties of RAFT (reversible addition-fragmentation chain transfer)-polymerized poly(stearyl acrylate) (PSA) was investigated. RAFT-polymerized PSA was prepared using 2-cyano-2-[(dodecylsulfanylthiocarbonyl) sulfanyl] propane (CDTP) with long alkyl group as a chain transfer agent and azobisisobutyronitrile (AIBN) as an initiator. The RAFT polymerization resulted in the polymerized structure having trithiocarbonyl (TTC) at one end and isobutyronitrile at the other end. RAFT-polymerized PSA was prepared with two different molecular weights. The TTC end group was replaced by isobutyronitrile using radical reaction with AIBN through optimization of the conditions, which resulted in isobutyronitrile at both ends. The effect of the end group on the thermal and structural properties was investigated using differential scanning calorimetry and X-ray diffraction, and the results indicated that the long alkyl group from TTC lowers the melting point and semi-crystalline structure in the case of low molecular weight PSA.

Short‐circuit defects caused by microscale dust particles in organic light‐emitting diodes (OLEDs) cause a decrease in production yield and hinder cost reduction. An organic layer coating by solution process is used to prevent short‐circuit defects of particles on a substrate. In this study, the coverage properties of a coated organic layer on size‐controlled particles are revealed. The surface of the substrate with size‐controlled SiO2 particles with a diameter of 0.2–5 µm is quantitatively contaminated, and the particle coverage properties of the solution‐processed hole injection layer are investigated. From the results of the leakage current measurement and cross‐sectional observation by a transmission electron microscope, it is observed that devices with 50 nm‐spin‐coated poly (3,4‐ethylenedioxythiophene): poly(styrene sulfonate) can cover SiO2 particles up to 1 µm in diameter without any increase in leakage current. It is revealed that larger‐sized particles cause electric defects, albeit with a low probability, owing to the larger space under the particles. To fabricate OLEDs with a high yield, the shape of the coverage at the bottom of the particle is important in preventing electric defects. The results of this study are useful not only for OLEDs but also for printed and coated devices. To prevent short‐circuit defects caused by dust particles on substrates, the particle coverage properties of the spin‐coated hole injection layer are reported. Quantitatively contaminating the substrate surface with size‐controlled SiO2 particles, poly(3,4‐ethylenedioxy‐thiophene):poly(styrene sulfonate) is spin‐coated, resulting in coverage up to SiO2 particles 10–20 times larger than the film thickness.

This work developed an electrically conductive thermosetting resin composite that transitioned from a liquid to solid without using solvents in response to an increase in temperature. This material has applications as a matrix for carbon fiber reinforced plastics. The composite comprised polyaniline (PANI) together with dodecyl benzene sulfonic acid (DBSA) as a liquid dopant in addition to a radical polymerization system made of triethylene glycol dimethacrylate with a peroxide initiator. In this system, micron-sized non-conductive PANI particles combined with DBSA were dispersed in the form of conductive nano-sized particles or on the molecular level after doping induced by a temperature increase. The thermal doping temperature was successfully lowered by decreasing the PANI particle size via bead milling. Selection of an appropriate peroxide initiator also allowed the radical polymerization temperature to be adjusted such that doping occurred prior to solidification. Optimization of the thermal doping temperature and the increased radical polymerization temperature provided the material with a high electrical conductivity of 1.45 S/cm.

Organic Light‐Emitting Diodes To prevent short‐circuit defects of OLEDs caused by dust particles on substrates, Yoshiyuki Suzuri and colleagues report on the particle coverage properties of the spin‐coated hole injection layer in article number 2201695. Quantitatively contaminating the substrate surface with size‐controlled SiO2 particles, PEDOT:PSS was spin‐coated, resulting in coverage up to SiO2 particles 10 to 20 times larger than the film thickness.

Electrowetting on dielectric (EWOD) devices were fabricated using two hydrophobic organic fluoropolymers, comprising CYTOP (a product name) having different chemical structures only at the terminal functional groups. These devices were subsequently characterized by applying a range of direct current (DC) voltages. The data demonstrated that the EWOD performance was dramatically improved upon incorporating a CYTOP polymer having highly polar terminal functional groups, as compared to a polymer having terminal groups with lower polarity. The new finding about the positive effect of highly polar terminal functional groups on the enhancement of EWOD was exhibited through various careful experiments, changing only the quantitative amount of polar terminal functional groups while keeping other factors constant (thickness, substrate, etc.).

The effects of compounds containing oxazoline groups and the presence of maleic anhydridegrafted polypropylene (PP-g-MAH) on the spectral, morphological, and tensile properties of polypropylene (PP)/liquid crystalline polymer (LCP) blends were investigated. A wholly aromatic LCP having a low melting point which was copolyester, namely AL-7000 have been used, because thermal decomposition ofPP and compatibilizer must be prevented. Compression molding was selected as the molding method because it allows molding with a small amount of sample. The binary blends ofPP and LCP showed a degradation of tensile properties compared to pure PP. However, the addition of 2,2'-bis(2-oxazoline) and PP-g-MAH as compatibilizers dramatically improved the dispersion of LCP in the PP matrix, resulting in improved tensile properties. In particular, the tensile elongation at break was significantly increased, and cohesive failure (breakage within the matrix rather than at the PP/LCP interface) was observed in scanning electron microscopy images.

Reactive extrusion of poly( L -lactide) (PLLA) was carried out in the presence of a small amount of various peroxides with relatively slow decomposition rates. The resulting crosslinked, four-armed randomly branched PLLA (χ-PLLA) was characterized by size exclusion chromatography equipped with multiangle laser light scattering (SEC-MALS), and the results were interpreted according to the type of peroxide used. A new component with a higher molecular weight than the original PLLA was observed in the SEC-MALS chromatograms of the χ-PLLA. The weight-averaged molecular weight ( M w ) of the χ-PLLA was found to increase with increasing effective radical number per PLLA precursor ( n ), where n is the overall hydrogen abstraction ability of peroxide times the mole ratio of radical to PLLA precursor molecule. This implies that the hydrogen abstraction ability is a good index for the crosslinking efficiency of PLLA. The extent of branching of χ-PLLA was estimated by the shrinking factor, g =〈 R g 2 〉 b /〈 R g 2 〉 l , and rationalized with n , where 〈 R g 2 〉 b and 〈 R g 2 〉 l are the mean square radii of gyration of branched and linear polymers with the same molecular weight, respectively. The nucleation and overall crystallization rate of χ-PLLA in the nonisothermal crystallization from the melt was discussed from the viewpoints of branching and entanglement density. Reactive extrusion of poly( L -latctide) (PLLA) was carried out in the presence of a small amount of various peroxides. The resulting crosslinked, four-armed randomly branched PLLA (χ-PLLA) was characterized by size exclusion chromatography fitted with multiangle laser light scattering and rationalized with the type of peroxide used. The extent of branching of χ-PLLA was estimated by the shrinking factor and was rationalized with the effective radical number per PLLA precursor n . The nucleation and overall crystallization rate of χ-PLLA in the nonisothermal crystallization from the melt was rationalized with branching and entanglement density.

The modification of polymer chain ends is important in order to produce highly functional polymers. A novel chain-end modification of polymer iodides (Polymer-I) via reversible complexation-mediated polymerization (RCMP) with different functionalized radical generation agents, such as azo compounds and organic peroxides, was developed. This reaction was comprehensively studied for three different polymers, i.e., poly (methyl methacrylate), polystyrene and poly (n-butyl acrylate) (PBA), two different functional azo compounds with aliphatic alkyl and carboxy groups, three different functional diacyl peroxides with aliphatic alkyl, aromatic, and carboxy groups, and one peroxydicarbonate with an aliphatic alkyl group. The reaction mechanism was probed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The combination of PBA-I, iodine abstraction catalyst and different functional diacyl peroxides enabled higher chain-end modification to desired moieties from the diacyl peroxide. The dominant key factors for efficiency in this chain-end modification mechanism were the combination rate constant and the amount of radicals generated per unit of time.