Shin Horiuchi

Compatibilizing effect of maleic anhydride functionalized SEBS triblock elastomer through a reaction induced phase formation in the blends of polyamide6 and polycarbonate: 2. Mechanical properties

Abstract The relationship between mechanical properties and phase morphology of blends of polyamide6 (PA6) and polycarbonate (PC) compatibilized with a maleic anhydride functionalized poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer (SEBS-gMA) were explored. The in situ chemical reaction between the maleic anhydride of SEBS and the amine end group of PA6 during melt mixing induces the encapsulation of SEBS-gMA on the PC domains in PA6 rich blends. Through this phase formation, the adhesion on the domain boundary between PA6 and PC are improved and thus mechanical properties are improved. The use of the combination of SEBS-gMA and unfunctionalized SEBS as compatibilizers has been found to provide remarkable improvement of mechanical properties in the PA6/PC blends. A transmission electron microscope (TEM) study has revealed that the encapsulation of SEBS around the PC domains becomes gradually incomplete by the use of both SEBS-gMA and unfunctionalized SEBS in the PA6 rich blends and at the same time the dispersed SEBS domains in the PA6 matrix enlarge with increasing the ratio of unfunctionalized SEBS to SEBS-gMA. In addition, the SEBS phase encapsulating the PC domains become thicker accompanying with the incompletion of the encapsulation. Although the encapsulation is incomplete, maximum impact strength and maximum strain at break in tensile test can be obtained when certain combinations of SEBS-gMA and SEBS are used. The observation of the domain boundary TEM has revealed that the thicker SEBS phase on the domain boundary contains the micro domain structure of SEBS, where the polystyrene phase forms a cylinder in a hexagonal arrangement in the poly(ethylene-co-butylene) matrix. Through this micro domain structure, SEBS is assumed to perform as a thermoplastic elastomer and toughen the domain boundary between PA6 and PC.

Compatibilizing effect of a maleic anhydride functionalized SEBS triblock elastomer through a reaction induced phase formation in the blends of polyamide 6 and polycarbonate: 1. Morphology and interfacial situation

The result of a study on the effect of poly[styrene-b-(methylene-co-butylene)-b-styrene] triblock copolymer functionalized by maleic anhydride (SEBS-gMA) on the morphology and interface of the incompatible polymer blends of polyamide 6 (PA6) and polycarbonate (PC) is presented. The electron spectroscopic imaging with transmission electron microscopy was introduced to investigate the morphological features and interfacial situation of these blends. It has been found that the functionalized SEBS is dispersed in PA6 phase at about 50 nm in diameter and also exists on the domain boundary of PA6 and PC to envelope the PC domains in the blends with a matrix of PA6, while the unmodified SEBS attaches to PC particles but does not surround the domains. This means that the in situ reaction between PA6 and SEBS-gMA during mixing induces the envelop formation of SEBS on PC domains. The formation of SEBS-gMA phase on the interface works as a coupling agent to improve interfacial adhesion between PA6 and PC, which leads to the disappearance of voids on the domain boundary generated due to the different volume shrinkage between PA6 and PC in fast cooling in a mould. In the PC rich blends, SEBS-gMA is occluded in PA6 domains and exists on the interface between PA6 and PC, while with unmodified SEBS the dispersed SEBS and PA6 phases form separate dispersed phase in PC matrix. Dynamic mechanical analysis has revealed that the glass transition temperatures (Tgs) of PA6 and PC phases in the blends are slightly lower than the respective pure polymers and that the incorporation of SEBS-gMA does not affect the Tgs of each phase. This indicates that chemical reactions between PA6 and PC during melt mixing, which produce low molecular weight species of PC occurred regardless of the incorporation of SEBS-gMA and that SEBS-gMA on the domain boundary is not miscible enough to reside within the PC domains.

Core−Shell Structures of Silica−Organic Pigment Nanohybrids Visualized by Electron Spectroscopic Imaging

Energy-filtering electron transmission spectroscopy observation has been achieved to elucidate the nanostructures of powdery nanohybrids, which were produced by the dry mechanical milling of organic pigments and silica nanoparticles. The hybrids possess core-shell structures, irrespective of the levels of aggregation of primary particles, whereas hollow sites of aggregates of primary silica particles were filled with the pigment, leading to the locally concentrated distribution of the pigment to reduce the surface areas of the hybrids. The results imply that nanohybridization is referred to as the buildup method, although mechanical tools and procedures are quite the same as those for the conventional breakdown method.

Preparation and Characterization of Imogolite/DNA Hybrid Hydrogels

Imogolite is one of the clay minerals contained in volcanic ash soils. The novel hybrid hydrogels were prepared from imogolite nanofibers and DNA by utilizing strong interaction between the aluminol groups on imogolite surface and phosphate groups of DNA. The hybrid hydrogels of imogolite and DNA were prepared in various feed ratios, and their physicochemical properties and molecular aggregation states were investigated in both dispersion and gel states. The maximum DNA content in the hybrid gels was shown in equivalent molar ratio of imogolite and DNA. The physical properties of the hybrid gels were changed by varying DNA blend ratios. In the dispersion state, the hybrid gels showed a fibrous structure of imogolite, whereas a continuous network structure was observed in pure imogolite, indicating that the hybrid with DNA enhanced the dispersion of imogolite. In the gel state, DNA and imogolite nanofibers formed a 3D network structure.

Compatibilizing effect of a maleic anhydride functionalized SEBS triblock elastomer through a reaction induced phase formation in the blends of polyamide6 and polycarbonate-III. Microscopic studies on the deformation mechanism

Abstract Microscopic studies on the deformation mechanism of the blends of polyamide6 (PA6) and polycarbonate (PC) compatibilized with triblock copolymer of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) functionalized with maleic anhydride (SEBSgMA) were carried out. As described in our previous paper, significant improvement of mechanical properties of this blend series can be achieved by the use of the combination of SEBSgMA and unmodified SEBS (unSEBS) as compatibilizers. Especially, when the composition of the blends of PA6/PC is 75 25 and the total amount of added SEBS is 20 phr, drastic enhancement of the impact strength and of the elongation at break in the tensile stress-strain tests can be achieved by varying the ratio of SEBSgMA to unSEBS. The encapsulation by SEBS on the PC domains gradually become incomplete as the increase of the ratio of unSEBS to SEBSgMA and then the mechanical properties can be maximized. We observed the deformed zone of the specimens loaded to the tensile stress-strain tests and to the Izod impact tests using transmission electron microscopy (TEM) in order to find out the origin of this enhancement of the mechanical properties. It has revealed that voids tend to be generated at the PA6/PC interface easily due to the incompletion of the encapsulation achieved by the use of the combination of SEBSgMA and unSEBS, and thereby the local shear yielding of the matrix is promoted to dissipate the tensile and the impact energy.

Patterning of J-aggregated dyes using directed self-assembly on micro- and nanopatterned templates fabricated from phase-separated mixed Langmuir-Blodgett films

We report a useful technique for the deposition of dyes in the form of J-aggregates using directed self-assembly on the micro- and nanopatterned templates fabricated from the phase-separated mixed Langmuir-Blodgett (LB) films. The patterns of the mixed LB films can be tuned by adjusting the intermolecular interactions between the film-forming molecules. We used the mixed LB films containing silane coupling agent for the fabrication of micro- and nanopatterned templates, taking advantage of the difference between the surface free energy of the patterned regions and that of the self-assembled monolayers of the silane coupling agent. Atomic force microscopy showed that dyes were deposited by casting, spin-coating and the LB technique in accordance with the patterns of the original mixed LB films. Emission spectroscopy revealed that J-aggregates were formed in the patterned films. We succeeded in obtaining nanopatterns of a cyanine dye in the form of J-aggregates on the templates.

Angular-resolved EELS of a carbon nanotube

Abstract Electron energy loss spectroscopy (EELS) and electron spectroscopic imaging techniques are applied to a carbon nanotube (NT) to reveal the fine electronic state in the cylindrical structure of graphite. Although NTs with large diameters show similar EELS patterns at the carbon K-edge (285 eV) to those of graphite, a fine molecular straw with a diameter less than 5 nm exhibits different features. Especially it was found that the angular-resolved EELS formed by electrons scattered normal to the longitudinal axis of the NT indicates a strong contribution of π∗ excitation compared with σ∗ excitation. It confirms that the anisotropy of the NT exists in the structure and electronic structure.

Patterned surfaces in self-organized block copolymer films with hexagonally ordered microporous structures

A novel fabrication of the patterned surfaces in the polymer films was demonstrated by using the selforganizing character of the block copolymers of polystyrene-b-oligothiophenes and polystyrene-b-aromatic amide dendron. Hexagonally arranged open pores with a micrometer-size were spontaneously formed by casting the polymer solutions under a moist air flow. The amphiphilic character of the block copolymers played the crucial role as a surfactant to stabilize the inverse emulsion of water in the organic solvent, and subsequently the aggregated structure of the hydrophilic oligothiophene or aromatic amide dendron segments remained on the interiors of the micropores. The chemical composition on the top of the surface of the microporous films was characterized by energy-filtering transmission electron microscopy (EFTEM) or a time-of-flight secondary ion mass spectrometer (ToF-SIMS). The characterizations clearly indicated that the patterned surfaces in the self-organized block copolymer films with the hexagonally ordered microporous structures were fabricated in a single step.

Fracture toughness and morphology study of ternary blends of epoxy, poly(ether sulfone) and acrylonitrile-butadiene rubber

Abstract An epoxy resin based on diglycidyl ether of bisphenol A has been modified with poly(ether sulfone) (PES) and poly(acrylonitrile-co-butadiene) rubber (NBR) and cured with 4,4′-diaminodiphenylsulfone. The fracture behaviour of the ternary blend was examined using a fracture mechanics approach. Depending on the combination of PES and NBR, two distinct morphological states were shown, and the fracture behaviour varied from brittle to ductile with changing morphology. From fracture surface observations by scanning electron microscopy, the ternary blends that showed ductile fracture behaviour have a phase-inverted morphology in which the NBR-rich phase formed a continuous matrix, the epoxy-rich phase formed particles and the PES-rich phase also formed particles around the epoxy particles. Dynamic mechanical thermal analysis revealed that the ternary blends exhibited high Tg, as high as the Tg of the unmodified epoxy resin.

Properties of core–shell structured nanopowders of molecular crystals fabricated by dry grinding

A generic way to prepare nano-sized molecular crystals in large scale is described. The dry mechanical grinding of a mixture of molecular crystals with surface-modified Stober silica nanoparticles gave voluminous hybridised powders with core–shell nanostructures, which were revealed by TEM and EFTEM measurements. Fluorescence spectra of the hybrids of emissive crystals suggested that crystal structures of the bulk are preserved even after the milling. Calorimetric measurements disclosed that melting points of crystals are lowered as a result of the nanohybridisation and that the depression of melting point and heat of fusion are reversibly proportional to shell thickness.