Transmission Electron Microtomography Research Articles

Direct Three-dimensional Visualization and Morphological Analysis of Fuel Cell Electrodes by Transmission Electron Micro-tomography

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Three-Dimensional Visualization of a Single Block Copolymer in Lamellar Nanodomains

The single-chain distribution in a poly(styrene-block-isoprene) block copolymer in the bulk state was studied by the combined method of transmission electron microtomography and three-dimensional mesoscale computer simulations. The local frustration of the block chains on a nanoscale can be analyzed using the size of the gyration radius, Rg. Two representative morphologies in the lamellar morphology have been examined, i. e., flat and bent lamellae. The Rg obtained from the proposed new method gave reasonable agreement with the previously measured values. It was shown that the single polymer chains in the bent lamella is more stretched out than those in the flat lamella. This method provides a new insight into understanding the self-assembled structure in the bulk microdomains.

Mesoscopic Mechanical Analysis of Filled Elastomer with 3D-Finite Element Analysis and Transmission Electron Microtomography

Abstract Analysis of deformation of the filled elastomer in mesoscopic scale was investigated with 3-D FEM (Finite Element Analysis). Combination of 3-D TEMT (Transmission Electron Micro Tomography) and Voxel-FEM enables us to reconstruct mesoscopic scale 3-D image and calculate 3-D strain distribution. To the first approximation, the calculated stress-strain behavior shows a good agreement with the experimental results. The strain concentration over 200% can be seen between carbon black aggregates, even if the overall strain is only 15%. The rubber occluded by carbon black aggregates can also be observed. The virtual rubber model constructed with perfectly dispersed fillers was also calculated. This shows less overall stress than that of the actual filled model reconstructed with 3-D TEMT image. It is found that the occluded rubber can behave as a hard domain and is an important factor of the filler reinforcement effect on rubber.

Three-dimensional Structural Analysis on Multi-component Polymer Materials by Transmission Electron Microtomography

Three-dimensional Structural Analysis on Multi-component Polymer Materials by Transmission Electron Microtomography

Direct Three-Dimensional Observations of Order-Order Transition from Gyroid to Cylindrical Structures in a Block Copolymer

An order-order transition (OOT) from the bicontinuous double-gyroid (G) structure to the hexagonally-packed cylindrical (C) structure in a poly(styrene-block-isoprene) (SI) block copolymer was investigated by transmission electron microtomography (TEMT). The coexistence of the G and C microdomains during the OOT was observed. The boundary structures between the G and C microdomains were directly three-dimensionally visualized. It was found that the {220} plane of the G structure changed to the {110} plane of the newlygenerated C structure, consistent with Matsen’s prediction from his computer simulations based on self-consistent field (SCF) theory.

Observation of the Three-Dimensional Structure of Actin Bundles Formed with Polycations

Three-dimensional structures of actin bundles formed with polycations were observed by using transmission electron microtomography and atomic force microscopy. We found, for the first time, that the cross-sectional morphology of actin bundles depends on the polycation species and ionic strength, while it is insensitive to the degree of polymerization and concentration of polycation. Actin bundles formed with poly-N-[3-(dimethylamino)propyl] acrylamide methyl chloride quaternary show a ribbon-like cross-sectional morphology in low salt concentrations that changes to cylindrical cross-sectional morphology with hexagonal packing of the actin filaments in high salt concentrations. Contrastingly, actin bundles formed with poly-L-lysine show triangular cross-sectional morphology with hexagonal packing of the actin filaments. These variations in cross-sectional morphology are discussed in terms of anisotropy in the electrostatic energy barrier.

Maximum diameter of the rod-shaped specimen for transmission electron microtomography without the “missing wedge”

In our recent study, the complete rotation of a rod-shaped specimen during transmission electron microscopy (TEM) has been successfully carried out, yielding a truly quantitative three-dimensional (3D) structure of a ZrO 2/polymer nano-composite. This result allows the further development of transmission electron microtomography (TEMT) for materials science. The diameter of the rod-shaped specimen was about 150 nm, which may not be statistically large enough to evaluate structural parameters, e.g., volume fraction of Zr nano-particles. Thus, it is preferable to image rods with larger diameters in 3D. In this study, several rod-shaped specimens whose diameters ranged from 150 to 530 nm were subjected to the “distortion-free TEMT”. The maximum diameters, l, observable under 200 and 300 kV-TEMTs were, respectively, 460–470 and 600–670 nm (corresponding the maximum relative diameters, l / λ ( λ : mean free path), were ca. 2.2 and 2.7–3.0).

A Neutron Reflectivity Study on a Terraced Lamellar Morphology in a Block Copolymer Thin Film

A microphase-separated structure of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer thin film was studied by neutron reflectivity (NR). The spun-coated dPS-b-P2VP block copolymer (on a Si substrate) showed the coexistence of a minority thin lamellar layer (holes) dispersed in a majority thick layer. The “terraced structure” was formed due to the mismatch between the initial film thickness and the intrinsic lamellar periodicity of the dPS-b-P2VP block copolymer. The amount and height of the holes were evaluated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and transmission electron microtomography (TEMT). The three-dimensional (3D) images obtained from the TEMT experiments clearly showed that the microphase-separated structure inside the thin film was homeotropically aligned. The thickness of the thick and the thin lamellar layers corresponded to (5/2)L0 and (3/2)L0, respectively (L0 is the lamella periodicity in the bulk state). The NR profile from the dPS-b-P2VP thin film, Rexp, showed many distinctive scattering peaks. Based on the structural information obtained from the microscopy, a scattering length density profile along the depth direction, i.e., the direction normal to the film surface, b/vTEMT, was evaluated, which was then used as an initial profile in the conventional model fitting method. An excellent best-fit to Rexp was obtained using b/vTEMT, even though the thin film had the terraced structure. The surface coverage of the holes was estimated from the resulting b/v, which was in good agreement with the estimated value from TEM.

A Novel Structural Analysis for a Cylinder-Forming Block Copolymer Thin Film Using Neutron Reflectivity Aided by Transmission Electron Microtomography

Microphase-separated structures of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer in thin films were studied by neutron reflectivity (NR) and transmission electron microtomography (TEMT). The dPS-b-P2VP block copolymer shows a cylindrical morphology in the bulk state. The block copolymer was spun-coated on a Si substrate, which was extensively annealed (170 °C for 14 days) before the NR experiments. The annealed thin film showed a featureless NR profile, the reflectivity monotonically decreased with the increasing scattering vector along the depth direction of the thin film, qz. The portion of the dPS-b-P2VP block copolymer thin film used in the NR experiment was examined by TEMT, from which a three-dimensional (3D) morphology of the block copolymer thin film was successfully obtained. The 3D image clearly showed that the microphase-separated structure inside the thin film had a cylindrical morphology with some order along the depth, but almost no in-plane order. In order to...

Three-Dimensional Structure of a Nanocomposite Material Consisting of Two Kinds of Nanofillers and Rubbery Matrix Studied by Transmission Electron Microtomography

The three-dimensional (3D) morphology of particulate fillers embedded in a rubbery matrix was examined by transmission electron microtomography (TEMT). Two types of nanofillers, i.e., carbon black (CB) and silica (Si) nanoparticles, were used as the nanofillers. Although the CB and Si nanoparticles were difficult to distinguish by conventional transmission electron microscopy (TEM), they appeared different by TEMT; the CB and Si nanoparticles appeared to be hollow and solid particles in the cross-sectional images of the TEMT 3D reconstruction, respectively, demonstrating that TEMT itself provided a unique particle-discriminative function. The nanoparticles were found to form aggregates in the matrix. It is intriguing that each aggregate was made of only one species; not a single aggregate contained both the CB and Si nanoparticles. A particle-packing algorithm was developed to estimate the positions of each primary nanoparticle inside the aggregates.

AxBAx‐Type Block–Graft Polymers with Soft Methacrylate Middle Segments and Hard Styrene Outer Grafts: Synthesis, Morphology, and Mechanical Properties

Novel copolymers with controlled architectures can function as new building blocks for well-defined nanostructures on the basis of microphase separation, unlike conventional ABA triblock copolymers. A series of well-defined A(x)BA(x)-type block-graft copolymers consisting of soft middle segments (dodecyl methacrylate (DMA)) and hard outer graft chains (styrene (St)) were synthesized by ruthenium-catalyzed living radical block and graft polymerization. NMR spectroscopy and size-exclusion chromatography combined with multiangle laser light scattering confirmed the well-defined structure of the A(x)BA(x) block-graft copolymers with backbones and graft chains of controlled lengths. Transmission electron microscopy and transmission electron microtomography revealed a series of morphologies for the copolymers. Morphological changes were observed from PSt "honeycomb" cylinders to lamellae and poly(DMA) cylinders with increasing PSt-graft content, whereby the phase diagram was shifted significantly to lower volume fractions of the larger-number component (St) relative to those of the corresponding ABA triblock copolymers. More specifically, poly(DMA) cylinders were observed even before the St content reached 50 wt %. The A(x)BA(x) and ABA copolymers with 17-30 wt % of St exhibited characteristics of a thermoplastic elastomer with tensile strengths of 1-6 MPa and elongations at break of 70-300 %. These mechanical properties can be related well to the microphase structures of the A(x)BA(x) and ABA copolymers.

Three‐dimensional structural analysis of a block copolymer by scanning electron microscopy combined with a focused ion beam

AbstractA three‐dimensional (3D) lamellar structure of a poly(styrene‐block‐isoprene) block copolymer was observed at submicrometer and micrometer levels by scanning electron microscopy combined with a focused ion beam (FIB–SEM). The 3D lamellar structure with an exceptionally large periodicity, about 0.1 μm, was successfully reconstructed, and the size of the reconstructed image by FIB–SEM was 6.0 × 6.0 × 4.0 μm3, which was greater than the transmission electron microtomography data, 3.8 × 3.9 × 0.24 μm3, by a factor of about 40. This result indicates that 3D reconstruction using FIB–SEM is quite useful for direct 3D observations, especially analyses of polymeric materials at the submicrometer and micrometer levels. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 677–683, 2007

Three-Dimensional Imaging in Polymer Science: Its Application to Block Copolymer Morphologies and Rubber Composites

New methods to visualize polymer morphologies in three-dimension (3D) in polymer science are reviewed. Here we concentrate on one of such 3D imaging technique, transmission electron microtomography (TEMT), and introduce some experimental studies using this novel technique. They are block copolymer morphologies during order-order transition between the two different morphologies and block copolymer thin film morphology also during morphological change due to confinement. Direct visualization of 3D structure of silica particle/rubber composite and related morphological analyses are shown. Subsequently, as a very hot topic of the 3D imaging, we show for the first time to characterize the morphological change in a silica particle/rubber composite upon stretching. It was found that the aggregates of silica particles were broken down upon stretching and many voids were generated near and between the silica particles. Local stress upon stretching inside the composite was inferred from the image intensity of the 3D reconstructed image. The local stress was found not only near the silica particles but also near the top of the voids. The observations indicated that the local stress increases the modulus, causing voids to form along the stretching direction. The thickness of the specimen after the stretching was also estimated from the 3D volume data, which turned out to be non-uniform and thinner than what is expected from the affine deformation. These experimental findings indicate that the rubber composite does not obey the assumption of the affine deformation at the nano-scale.

電子線トモグラフィーによる酸化チタン光触媒材料の反応表面の研究

電子線トモグラフィーによる酸化チタン光触媒材料の反応表面の研究

電子線トモグラフィー法を用いた三次元構造解析

Recently, three-dimensional (3D) direct observations and analysis of polymer morphologies draw considerable attention because they not only provide intuitive understanding of the morphologies but also offer novel structural parameters that can never be obtained by other technique. The most sophisticated transmission electron microtomography (TEMT) achieves spatial resolution of less than 1 nm in the 3D reconstructed images. In the present paper, applications of TMET to polymer nanostructures, that is microphase-separated structures of block copolymers (Gyroid-structures), were reported in order to demonstrate huge and promising capabilities of the new technique.

Three‐Dimensional Observations of Grain Boundary Morphologies in a Cylinder‐Forming Block Copolymer

AbstractThe grain boundary morphology of a cylinder‐forming poly(styreneblock‐isoprene) (SI) diblock copolymer was investigated using transmission electron microtomography (TEMT). The three‐dimensional (3D) morphologies of the grain boundaries between the two grains with different orientation angle, α, were investigated. In the present study, two kinds of grain boundary morphologies, α ≃ 90° and α ≃ 120°, were examined in 3D. It was found that, in the case of α ≃ 90°, most of the cylindrical domains bent at the grain boundary in order not to intersect each other, while the cylindrical domains were found to be smoothly connected and were continuous in the case of α ≃ 120°. The observed morphologies indicated that the chain conformation inside the cylindrical microdomains plays more significant role than the segmental interaction between the two blocks.

A “ladder” Morphology in an ABC Triblock Copolymer

AbstractABC triblock copolymers are known to exhibit a wide variety of unique types of morphologies compared to AB diblock copolymers. In the present study, poly(styrene‐block‐(ethylene‐alt‐propylene)‐block‐(methyl methacrylate)) (SEPM) triblock copolymers were synthesized and their morphologies were extensively studied by transmission electron microtomography (TEMT). In the SEPM triblock copolymer, two kinds of morphologies coexist: One was the well‐known knitting morphology, and the other was a novel morphology called the “ladder morphology”. The ladder morphology was a major morphology in the SEPM copolymer, the stability of which was discussed in terms of the interfacial area and the solubility parameters between the three components.

3D Nanometer‐Scale Study of Coexisting Bicontinuous Morphologies in a Block Copolymer/Homopolymer Blend

AbstractSummary: Coexisting bicontinuous morphologies, one ordered and one disordered, are investigated in a macrophase‐separated poly(styrene‐block‐isoprene) diblock copolymer/homopolystyrene (SI/hS) blend. Two‐phase behavior is attributed to the relatively high hS/S mass ratio (0.92). According to its crystallographic signature and channel coordination as discerned from three‐dimensional (3D) images generated by transmission electron microtomography (TEMT), the ordered morphology is classified as gyroid. The 3D local and global topological characteristics of both bicontinuous morphologies as measured directly from TEMT images are reported. The disordered morphology is further compared with molecular‐field simulations to ascertain the spatial distribution of the constituent species within the blend, thereby demonstrating the utility of high‐resolution 3D imaging coupled with molecular‐level simulations. magnified image

Front Cover: Macromol. Rapid Commun. 17/2006

Front Cover: A block copolymer/homopolymer (AB/hA) blend exhibits coexisting bicontinuous morphologies, one ordered and the other disordered. Transmission electron microtomography is used to analyze the 3D features of both morphologies (right images), and complementary Mesodyn simulations identify the distributions of hA, A and B within the morphologies (lower images). Further details can be found in the article by H. Jinnai, H. Hasegawa,* Y. Nishikawa, G. J. A. Sevink, M. B. Braunfeld, D. A. Agard, and R. J. Spontak* on page 1424.

3-Dimentional Observation of Lamellar Structure of a High Density Polyethylene Using Transmission Electron Micro-tomography

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005