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Block copolymers (BCPs) under nanoscale confinement can self-assemble to form novel nanostructures that are not available in the bulk state. Particularly, the ordering process of block copolymers a...

By taking advantage of chirality transfer, nanonetwork with controlled chirality can be obtained from self-assembly., Nanonetwork-structured materials can be found in nature and synthetic materials. A double gyroid (DG) with a pair of chiral networks but opposite chirality can be formed from the self-assembly of diblock copolymers. For triblock terpolymers, an alternating gyroid (GA) with two chiral networks from distinct end blocks can be formed; however, the network chirality could be positive or negative arbitrarily, giving an achiral phase. Here, by taking advantage of chirality transfer at different length scales, GA with controlled chirality can be achieved through the self-assembly of a chiral triblock terpolymer. With the homochiral evolution from monomer to multichain domain morphology through self-assembly, the triblock terpolymer composed of a chiral end block with a single-handed helical polymer chain gives the chiral network from the chiral end block having a particular handed network. Our real-space analyses reveal the preferred chiral sense of the network in the GA, leading to a chiral phase.

This review describes contemporary advancements in the study of interfacial morphologies and associated processes of multicomponent polymers. A particular emphasis is placed on the use of three-dimensional (3D) microscopy, for example, transmission electron microtomography (TEMT) and laser scanning confocal microscopy (LSCM). The time evolution of a spinodal interface during the phase separation of a polymer blend was followed by LSCM. The obtained 3D interfacial morphology was analyzed by differential geometry. The scalability was tested using curvature distributions. 3D nanoimaging, that is, TEMT, was applied to examine the stability and dynamics of complex block copolymer (BCP) morphologies, and novel structural data were directly assessed according to the 3D volume data. This review also examines two essential developments in the time-dependent in situ electron tomography of polymer materials to study the dynamic processes of BCPs. The 3D microscopy-based structural information renders an important perspective into the studies of nonlinear nonequilibrium occurrences as well as the statistical physics of long-chain-bearing moieties. Interfacial morphologies and associated processes in multicomponent polymer systems, e.g., block copolymers (BCPs) and polymer blends, are examined using three-dimensional (3D) microscopies. Because of the rich structural information in 3D images, various new types of structural parameters, including chain conformation inside BCPs nanodomains, chain packing frustration in BCPs, Genus etc., can be obtained. The stability and interfacial dynamics are also discussed.

We investigate the formation of the ordered bicontinuous structures in a stereoregular diblock copolymer, isotactic polypropylene-block-polystyrene (iPP-b-PS), in which the minority PP block possessed isotactic configuration. This diblock displayed the conventional ordered bicontinuous double gyroid (OBDG) morphology upon heating above the crystal melting point of the iPP block from the as-cast state. The OBDG phase remained stable in the heating process up to the order–disorder transition. In the subsequent cooling process from the nearly disordered state, the OBDG phase first developed, but when the temperature was sufficiently low, an order–order transition from OBDG to the ordered bicontinuous double diamond (OBDD) phase occurred, and OBDD eventually became the dominant structure. The results attested that OBDD and OBDG represented the thermodynamically stable structure at the lower and the higher temperature, respectively, and the OBDG morphology formed in the as-cast state was metastable. The presen...

Triply-periodic networks (TPNs), like the well-known gyroid and diamond network phases, abound in soft matter assemblies, from block copolymers (BCPs), lyotropic liquid crystals and surfactants to functional architectures in biology. While TPNs are, in reality, volume-filling patterns of spatially-varying molecular composition, physical and structural models most often reduce their structure to lower-dimensional geometric objects: the {\it 2D interfaces} between chemical domains; and the {\it 1D skeletons} that thread through inter-connected, tubular domains. These lower-dimensional structures provide a useful basis of comparison to idealized geometries based on triply-periodic minimal, or constant-mean curvature surfaces, and shed important light on the spatially heterogeneous packing of molecular constituents that form the networks. Here, we propose a simple, efficient and flexible method to extract a 1D skeleton from 3D volume composition data of self-assembled networks. We apply this method to both self-consistent field theory predictions as well as experimental electron microtomography reconstructions of the double-gyroid phase of an ABA triblock copolymer. We further demonstrate how the analysis of 1D skeleton, 2D inter-domain surfaces, and combinations therefore, provide physical and structural insight into TPNs, across multiple length scales. Specifically, we propose and compare simple measures of {\it network chirality} as well as {\it domain thickness}, and analyze their spatial and statistical distributions in both ideal (theoretical) and non-ideal (experimental) double gyroid assemblies., 13 pages, 7 figures, 3 pages supporting pdf

Self-assembling structures and their dynamical processes in polymeric systems have been investigated using three-dimensional transmission electron microscopy (3D-TEM). Block copolymers (BCPs) self-assemble into nanoscale periodic structures called microphase-separated structures, a deep understanding of which is important for creating nanomaterials with superior physical properties, such as high-performance membranes with well-defined pore size and high-density data storage media. Because microphase-separated structures have become increasingly complicated with advances in precision polymerization, characterizing these complex morphologies is becoming increasingly difficult. Thus, microscopes capable of obtaining 3D images are required. In this article, we demonstrate that 3D-TEM is an essential tool for studying BCP nanostructures, especially those self-assembled during dynamical processes and under confined conditions. The first example is a dynamical process called order-order transitions (OOTs). Upon changing temperature or pressure or applying an external field, such as a shear flow or electric field, BCP nanostructures transform from one type of structure to another. The OOTs are examined by freezing the specimens in the middle of the OOT and then observing the boundary structures between the preexisting and newly formed nanostructures in three-dimensions. In an OOT between the bicontinuous double gyroid and hexagonally packed cylindrical structures, two different types of epitaxial phase transition paths are found. Interestingly, the paths depend on the direction of the OOT. The second example is BCP self-assemblies under confinement that have been examined by 3D-TEM. A variety of intriguing and very complicated 3D morphologies can be formed even from the BCPs that self-assemble into simple nanostructures, such as lamellar and cylindrical structures in the bulk (in free space). Although 3D-TEM is becoming more frequently used for detailed morphological investigations, it is generally used to study static nanostructures. Although OOTs are dynamical processes, the actual experiment is done in the static state, through a detailed morphological study of a snapshot taken during the OOT. Developing time-dependent nanoscale 3D imaging has become a hot topic. Here, the two main problems preventing the development of in situ electron tomography for polymer materials are addressed. First, the staining protocol often used to enhance contrast for electrons is replaced by a new contrast enhancement based on chemical differences between polymers. In this case, no staining is necessary. Second, a new 3D reconstruction algorithm allows us to obtain a high-contrast, quantitative 3D image from fewer projections than is required for the conventional algorithm to achieve similar contrast, reducing the number of projections and thus the electron beam dose. Combining these two new developments is expected to open new doors to 3D in situ real-time structural observation of polymer materials.

To develop molecularly based interpretations of the two-dimensional scattering patterns (2DSPs) of phase-separated block copolymers (BCPs), we performed coarse-grained molecular dynamics simulations of ABA tri-BCPs under uniaxial stretching for block-fractions where the A-segment (glassy domain) is smaller than the B-segment (rubbery domain), and estimated the behaviour of their 2DSPs. In BCP stretching experiments, mechanical properties are generally evaluated using a stress–strain curve. We obtained 2DSPs with different contrasts for the A- and B-segments, which are indicative of the differences between X-ray and neutron scattering experiments. The small- and wide-angle behaviours of the 2DSPs originate from the morphologies of the phase-separated domains and local bond orientations, respectively. When the block-fractions are changed for a constant stress value on the stress–strain (SS) curve, the brightness of the spots in the wide-angle region of the A- and B-segment-dominant 2DSPs decreases and increases with increasing strain, respectively. We can regard the systematic changes in the small-angle 2DSPs of the glassy domain and the wide-angle 2DSPs of the rubbery domain with changes in the SS-curve as a structure–property relationship.

The three-dimensional (3D) confinement effect on the microphase-separated structure of a diblock copolymer was investigated both experimentally and computationally. Block copolymer nanoparticles were prepared by adding a poor solvent into a block copolymer solution and subsequently evaporating the good solvent. The 3D structures of the nanoparticles were quantitatively determined with transmission electron microtomography (TEMT). TEMT observations revealed that various complex structures, including tennis-ball, mushroom-like, and multipod structures, were formed in the 3D confinement. Detailed structural analysis, showed that one block of the diblock copolymer slightly prefers to segregate into the particle surface compared with the other block. The observed structures were further elaborated using cell dynamics computer simulation

Interface manipulation to pursue unusual nanostructures was performed using a strategically designed triblock terpolymer with a short middle segment, poly(styrene-b-methyl methacrylate-b-2,2,2-trifluoroethyl methacrylate). A short middle segment of poly(methyl methacrylate) (PMMA) that does not form any distinct domains was found to play an important role in manipulating the interface between the polystyrene (PS) and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) domains and forming unconventional partially continuous oblate cylinders with an oblique lattice, as confirmed by small angle X-ray scattering (SAXS) and dual-axis transmission electron microtomography (TEMT). Interface manipulation to pursue unusual nanostructures was performed using a strategically designed triblock terpolymer with a short middle segment, poly(styrene-b-methyl methacrylate-b-2,2,2-trifluoroethyl methacrylate). A short middle segment of poly(methyl methacrylate) (PMMA) that does not form any distinct domains was found to play an important role in manipulating the interface between the polystyrene (PS) and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) domains and forming unconventional partially continuous oblate cylinders with an oblique lattice, as confirmed by small angle X-ray scattering (SAXS) and dual-axis transmission electron microtomography (TEMT).

We demonstrated the controlled incorporation of Au nanoparticle grafted with polystyrene (PS) molecules in the helical microdomains of ABC-type linear triblock terpolymers composed of PS, polyisoprene (PI) and poly(methyl methacrylate) (PMMA). The Au nanoparticles grafted with three PSs with different molecular weights were synthesized and incorporated into the terpolymer films. The morphologies of composite films and localization of Au nanoparticles were three-dimensionally characterized with transmission electron microtomography observation. By varying the molecular weights of grafted PS molecules on Au nanoparticles, their assemblies were successfully controlled in the double-helical microdomains.

Effect of frozen non-equilibrium structure for anisotropically deformed natural rubber with the nanomatrix structure on mechanical properties was investigated with respect to morphology analysis through 3D observation. Natural rubber with the nanomatrix structure was prepared by graft copolymerization of styrene onto natural rubber particles in latex stage followed by coagulation of the resulting latex. The morphology was observed by electron tomography and focused ion beam-scanning electron microscopy (FIB-SEM). The nanomatrix structure in isotropic state was precisely analyzed by electron tomography and synchrotron scattering technique. The nanomatrix structure was found to consist of natural rubber particles and polystyrene nanoparticles. The frequency-independent loss tangent at plateau region was attributed to the discontinuous nanomatrix structure. After annealing at 403 K and 7 MPa, the nanomatrix became continuous, which resulted in the increases in stress at strain of one and storage modulus as well as increase in loss tangent.

The ordered bicontinuous double diamond (OBDD) structure has long been believed to be an unstable ordered network nanostructure, which is relative to the ordered bicontinuous double gyroid (OBDG) structure for diblock copolymers. Using electron tomography, we present the first real-space observation of the thermodynamically stable OBDD structure in a diblock copolymer composed of a stereoregular block, syndiotactic polypropylene-block-polystyrene (sPP-b-PS), in which the sPP tetrapods are interconnected via a bicontinuous network with Pn3̄m symmetry. The OBDD structure underwent a thermally reversible order-order transition (OOT) to OBDG upon heating, and the transition was accompanied with a slight reduction of domain spacing, as demonstrated both experimentally and theoretically. The thermodynamic stability of the OBDD structure was attributed to the ability of the configurationally regular sPP block to form helical segments, even above its melting point, as the reduction of internal energy associated with the helix formation may effectively compensate the greater packing frustration in OBDD relative to that in the tripods of OBDG.

Block copolymer micelles have been extensively discussed for many decades because of their applications, such as lithography and drug delivery. However, controlling the morphologies of nanostructure assembly using block copolymer micelles as building elements remains a great challenge. In this work, we developed a novel route to induce micelle assembly in confined geometries. Polystyrene-block-polydimethylsiloxane (PS-b-PDMS) micelle solutions were used to prepare micelle nanostructures, and the critical parameters affecting the morphologies were determined. Micelle nanorods, micelle nanospheres, and multi-component nanopeapods were prepared by wetting anodic aluminum oxide (AAO) templates with micelle solutions. Rayleigh-instability-driven transformation was discovered to play an important role in controlling the morphologies of the micelle nanostructures. This study not only proposes a versatile approach to preparing block copolymer micelle nanostructures, but it also provides deeper insight into the controlling factors of block copolymer micelle morphologies in cylindrical confinement.

The control of microphase-separated structures in a poly(styrene-block-butadiene-block-methyl methacrylate) (SBM) was investigated in three dimensions by transmission electron microtomography. Neat SBM self-assembled into a double-helical structure of polybutadiene (PB) domains around hexagonally packed core polystyrene (PS) cylinders in a poly(methyl methacrylate) matrix. When PS homopolymer with a lower molecular weight than that of the PS block in SBM was added to the SBM, the PB domains transformed from double-helical structures to spherical domains, while maintaining the helical trajectories. In contrast, adding a higher molecular weight PS to the SBM changed the helical structures from double- to triple-stranded structures and even to four-stranded structures. The helical structures of the PB domains were strongly affected by the distribution of the blended polystyrenes in the core cylindrical PS domains.

We investigated, via scanning and transmission electron microscopy, the arrangement of the microdomains of symmetric polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) confined in hemispherical cavities. The hemispherical cavities were prepared by using anodic aluminum oxide (AAO) template, where the inner surface of the cavities was modified by thin brush layers of PS, PMMA, and PS-ran-PMMA copolymer. When the inner surface of the cavity is strongly selective to PS chains, concentric rings consisting of PS and PMMA microdomains are formed, replicating the confined geometry of hemisphere. However, as the selectivity of a brush to PS chains becomes weaker, various interesting morphologies are formed that have not been reported in the literature. The experimentally observed microdomain arrangement confined inside the hemispherical cavities was compared with the simulation results based on the dynamic Metropolis Monte Carlo method.

In this report, we show a simple route to fabricate Janus particles having magnetic nanoparticles inside them, which can respond and rotate along to magnetic fields. By solvent evaporation from the tetrahydrofran solution of polymer stabilized γ-Fe2O3 nanoparticles, polystyrene (PS), and polyisoprene containing water, aqueous dispersion of Janus microparticles were successfully prepared, and the γ-Fe2O3 nanoparticles were selectively introduced into the PS phase. We demonstrate rotation and accumulation of Janus particles by using a neodymium magnet.

Block copolymers synthesised in supercritical CO2 dispersion undergo in situ self-assembly which can result in a range of nanostructured microparticles. However, our previous study revealed that copolymers with different block combinations possessed different microphase separated morphologies at identical block volume fractions. In this paper, we follow up those initial observations. By examining the phase behaviour of a selection of structurally diverse block copolymers, we explore the structural factors which influence the conflicting self-assembly behaviours. The composition dependence of the morphology is found to be strongly related to the CO2-philicity of the second block relative to poly(methyl methacrylate) (PMMA). Whilst PMMA-b-poly(benzyl methacrylate) (PBzMA) and PMMA-b-poly(N, N-dimethylaminoethylmethacrylate) (PDMAEMA) phase behaviour follows traditional diblock copolymer phase diagrams, PMMA-b-poly(styrene) (PS) and PMMA-b-poly(4-vinyl pyridine) (P4VP), which comprise blocks with the greatest contrast in CO2-philicity, self-assemble into unexpected morphologies at several different block volume fractions. The morphology of these copolymers in the microparticulate form was found to revert to the predicted equilibrium morphology when the microparticles were re-cast as films and thermally annealed. These findings provide strong evidence that CO2 acts as a block-selective solvent during synthesis. The CO2-selectivity was exploited to fabricate various kinetically trapped non-lamellar morphologies in symmetrical PMMA-b-PS copolymers by tuning the ratio of polymer : CO2. Our data demonstrate that CO2 can be exploited as a facile process modification to control the self-assembly of block copolymers within particles.

We report on the formation of tetragonally perforated lamellae from a polybutadiene-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) (BVT) triblock terpolymer, PB22P2VP29PtBMA49110, ...

The orientation of nanoscale double-helical morphologies of SBM triblock terpolymer at various film thicknesses (h) were studied using transmission electron microtomography, following solvent annealing and drying at a controlled solvent evaporation rate (R). The combination of h and R were found to be essential factors to determine orientation of the double-helical microdomains in thin films. Perpendicularly aligned double-helical morphology extending several micrometers from the substrate to the air surface was achieved.

The effect of preferential wetting of one of the constituent block chains and corresponding block copolymer morphologies to a carbon substrate is studied from a molecular level. The single chain distribution of the block copolymer was estimated as a function of the distance from the substrate by a combined method of transmission electron microtomography (TEMT) and self-consistent field (SCF) simulation. The former provides three-dimensional (3D) morphological information of cylindrical microdomains near the surface, while the latter utilizes the 3D morphology to quantitatively determine the interaction between the block chains and substrate, which is further used to estimate the single chain distribution of one of the block chains, i.e., the subchain, of the matrix. It was found that the subchains in the vicinity of the wetting layer are substantially compressed, while the radius of gyration of the subchain at a distance L (L is the interlayer distance of the cylindrical microdomains from the substrate) has already reached the same value as that in the bulk, indicating that the propagation of the surface interaction is limited to one layer. The methodology developed in this study can be used not only to estimate the surface effect on polymer chains for a variety of different surfaces, but also to provide a means to understand complicated block copolymer morphologies from a molecular level.

Nanoparticles with concentric layered structures were generated from a lamellae-forming poly(styrene-b-isoprene) diblock copolymer using controlled precipitation from a tetrahydrofuran/water mixture. Chloroform, a good solvent for both blocks, was used to swell and anneal the nanoparticles suspended in aqueous media. The three-dimensional morphologies of particles were reconstructed by transmission electron microtomography throughout the process of solvent annealing. A transition from concentric lamellae to PI cylinders in a PS matrix occurred upon annealing, presumably due to a slight selectivity of chloroform for PS. These cylindrical microdomains were further divided into PS-core-PI-shell spherical structures in a PS matrix upon extended annealing, a structure that is unique among reported microphase separated morphologies of diblock copolymers.

Block copolymer nanopaticles were prepared from the mixture solutions containing good/poor solvents by a simple evaporation process. The block copolymers formed disorder, unidirectionally stacked lamellar, and onion-like structures in nanoparticles depending on preparation temperatures. Thermal annealing induced the disorder-order phase transition and order-order phase transformation in the block copolymer nanoparticles, even though the annealing temperature is lower than the of one polymer segment. The unusual thermal behaviors suggest that the glass transition temperature of the block copolymer is decreased by the effect of nanoparticle, whose surface areas are larger than their volumes.

Lamella-, cylinder-, and sphere-forming block copolymers (BCPs) of polystyrene-b-polybutadiene (PS-b-PBD) were drawn into the pores of anodized aluminum oxide (AAO) membranes in the melt by capillary forces. After thermal annealing, the nanorods of the BCP were removed by dissolution of the AAO with a weak acid, and transmission electron microscopy (TEM) was used to investigate the resultant morphologies of the confined BCPs. The diameters of the pores in the AAO and the molecular weight of the block copolymers were varied to investigate the effect of confinement on the microphase separation of the BCP. Concentric cylinders were observed for the lamella-forming BCPs under 2D confinement, and deviations of the lamella repeat period were measured as a function of AAO pore diameter. In addition, torus-like morphologies were observed as the degree of confinement increased. For the bulk cylinder-forming BCPs, a rich variety of morphologies, not seen in the bulk, were observed that included stacked torus-like m...

Microphase-separated structures in poly(styrene-block-isoprene) (SI) block copolymer thin films were investigated by transmission electron microtomography (TEMT). The SI block copolymer showed cylindrical microdomains in the bulk state. Several block copolymer thin films with different thicknesses were prepared by spin-coating and were extensively annealed before the TEMT experiments. Intriguingly, although the cylindrical morphology orienting parallel to the substrate was observed in most of the cases, spherical microdomains were found at certain film thicknesses. The thickness dependence was investigated using a computer simulation based on the self-consistent-field theory, producing a morphological phase diagram based on minimizing free energy. We find that the distortion of the hexagonal lattice of the cylindrical microdomains caused the morphological transition to the spherical microdomains.

Cylindrical nanoporous structures were prepared by using a mixture film of polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) and PMMA homopolymer (hPMMA), and they were analyzed by transmission electron microtomography (TEMT), X-ray reflectivity (XR), and grazing incidence small-angle X-ray scattering. For this purpose, the mixture film was spin-coated onto a silicon wafer modified by a neutral brush for PS and PMMA blocks, which generates PMMA cylindrical microdomains oriented normal to the substrate. Two methods were employed to prepare nanoporous structures: (1) all of the PMMA phase (PMMA block and PMMA homopolymer) in the film was removed by UV irradiation, followed by rinsing with a selective solvent (acetic acid) to PMMA and (2) only PMMA homopolymer was removed by selective solvent etching without UV irradiation. We found via TEMT and XR that the nanoporous structure in the film prepared by UV irradiation exhibited almost perfect cylindrical shape throughout the entire film thickness. However, when the film was rinsed with a selective solvent, nanoporous structures were not straight cylinders but had a funnel shape in which the diameter of nanopores located near the top of the film was larger than that located near the bottom of the film.

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.

The effect of various end-functional groups on the phase behavior of polystyrene-block-poly(n-butyl methacrylate) copolymer (PS-b-PnBMA) was investigated by using small-angle X-ray scattering, conventional and 3-D transmission electron microscopy, rheology, and Fourier-transformed infrared spectroscopy. A PS-b-PnBMA with maleic anhydride (SBM66-MAH) exhibited an unexpected thermoreversible transition occurring at higher temperature than its disorder-to-order transition temperature. The transition was very fast and induced a large increase in shear modulus. However, the transition at higher temperature was not observed in other PS-b-PnBMAs with carboxylic acid, diester, and hydrogen end groups.

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...

Ming Xiong, andHongxia Guo*State Key Laboratory of Polymer Physics and Chemistry,Joint Laboratory of Polymer Science and Materials,Institute of Chemistry, The Chinese Academy of Sciences,Beijing 100080, P. R. ChinaHiroshi Jinnai* and Takeshi KanekoDepartment of Macromolecular Science and Engineering,Graduate School of Science and Engineering,Kyoto Institute of Technology, Goshokaido-cho,Matsugasaki, Kyoto 606-8585, JapanReceiVed February 6, 2007ReVised Manuscript ReceiVed May 14, 2007Closure of block copolymer bilayer in the solution generatesthe so-called polymeric vesicles or polymersomes with thesolvent fills in their internal spaces. Recently, polymeric vesicleshave attracted a great attention not only from academia but alsofrom application field for drug delivery.

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.

A 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

The 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.

π-Complexes consisting of silver salts such as AgBF 4 and AgCF 3 SO 3 dissolved in poly(styrene- b -butadiene- b -styrene) (SBS) block copolymers have been prepared for use as facilitated olefin transport membranes. Facilitated olefin transport is not observable up to the silver mole fraction of 0.14, a threshold concentration, above which it increases almost linearly with the silver salt concentration. FT-IR spectra of these complexes show that silver ions selectively coordinate with the C C bonds of PB blocks up to the silver mole fraction of 0.14, and that the coordinative interaction of the silver ion with aliphatic C C is stronger than that with aromatic C C. Interestingly, the bicontinuous morphology of the neat SBS block copolymer prepared from THF solution persists in the SBS complex with the salt concentrations less than 0.14. At high silver salt concentrations, the PS domains are additionally coordinated by silver ions and thus the morphology transition occurs from bicontinuous to lamellar. The threshold silver concentration of 0.14 for the facilitated olefin transport is nearly coincident with the composition at which the silver ions start coordinating with the aromatic C C bonds of the PS blocks, suggesting their important role in determining overall transport properties. Therefore, we have shown that the transport properties of the SBS complex membranes are significantly affected by the coordinative interaction of the block copolymers with the silver ions and their membrane morphology.

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.

The grain boundary morphology of a lamella-forming poly(styrene-b-isoprene) (SI) diblock copolymer was investigated by transmission electron microtomography. The twist grain boundary, at which two lamellar nanodomains orthogonally intersect, was successfully observed in three dimensions (3D). A two-dimensional periodic minimal surface, the Scherk's first surface, was once hypothesized as a model of such a grain boundary morphology but never experimentally ascertained. The area-averaged curvatures of the interface between the PI and PS nanodomains as well as the interfacial area per unit volume suggested that the grain boundary morphology had characteristics of the saddlelike hyperbolic surface and was found to be quite similar to Scherk's first surface.

Fine metal particles (nanoparticles) stabilized on porous (polymeric) substrates can be considered as a model system of a high-performance catalyst. In the present study, the substrate was made using the periodic microphase-separated structure of a block copolymer as the template, and the Pd nanoparticles were formed inside the porous material by reduction of the Pd2+ ions with 1-propanol as the reductant. The three-dimensional morphology of such a polymer-Pd hybrid material was studied by transmission electron microtomography. The characteristic structural parameters of the hybrid, e.g., the penetration of the Pd nanoparticles into the polymer substrate, number density of the Pd nanoparticles, and size distribution of the Pd nanoparticles, were measured for the first time.

The electric field alignment of cylindrical microdomains in diblock copolymer thin films was studied using small-angle neutron scattering and transmission electron microscopy. The alignment process was followed with the block copolymer films in different initial states. Starting from a poorly ordered state, the cylindrical microdomain orientation was biased by the surface field that initially drove the cylindrical microdomains to be oriented parallel to the film surface. With further annealing, the cylinders were disrupted locally and formed ellipsoid-shaped microdomains that, with time, connected into cylindrical microdomains oriented in the field direction. Starting from an ordered state with cylinders parallel to the surface, the applied electric field enhanced fluctuations at the interfaces of the microdomains. The growth of the fluctuations continued until the cylindrical microdomains broke up into spherical microdomains, similar to that seen in the thermoreversible cylinder-to-sphere order−order tra...

Recent developments regarding charged multiblock copolymers that can form physical networks and exhibit robust mechanical properties herald new and exciting opportunities for contemporary technologies requiring amphiphilic attributes. Due to the presence of strong interactions, however, control over the phase behavior of such materials remains challenging, especially since their morphologies can be solvent-templated. In this study, transmission electron microscopy and microtomography are employed to examine the morphological characteristics of midblock-sulfonated pentablock ionomers prepared from solvents differing in polarity. Resultant images confirm that discrete, spherical ion-rich microdomains form in films cast from a relatively nonpolar solvent, whereas an apparently mixed morphology with a continuous ion-rich pathway is generated when the casting solvent is more highly polar. Detailed 3D analysis of the morphological characteristics confirms the coexistence of hexagonally-packed nonpolar cylinders and lamellae, which facilitates the diffusion of ions and/or other polar species through the nanostructured medium.

This paper reviews recent progress concerning polymeric self-assemblies in confined spaces, including phase-separated structures of polymer blends and block copolymers. Although a wide variety of polymer self-assemblies have been studied in terms of conventional parameters, such as blend ratio, interaction of constituent polymers, block ratio, and molecular weight, a series of unique structures appear when the systems are self-assembled under confined conditions. Due to the limited space for phase separation, the polymers in the confinement are frustrated, and the resulting morphologies are distinctly different from those formed in free space. We give an overview of experimental and theoretical studies of the frustrated morphologies. We begin by defining confinement with respect to dimensionality and surface properties, and then introduce methods for producing various shapes and sizes of three-dimensional confinement. Finally, we present morphological and application-oriented studies and discuss the prospects for this research area.

Controlling superstructure of binary nanoparticle mixtures in three dimensions from self-assembly opens enormous opportunities for the design of materials with unique properties. Here we report on how the intimate coupling of synthesis, in-depth electron tomographic characterization and theory enables exquisite control of superstructure in highly ordered porous three-dimensional continuous networks from single and binary mixtures of metal nanoparticles with a triblock terpolymer. Poly(isoprene-block-styrene-block-(N,N-dimethylamino)ethyl methacrylate) is synthesized and used as structure-directing agent for ligand-stabilized platinum and gold nanoparticles. Quantitative analysis provides insights into short- and long-range nanoparticle-nanoparticle correlations, and local and global contributions to structural chirality in the networks. Results provide synthesis criteria for next-generation mesoporous network superstructures from binary nanoparticle mixtures for potential applications in areas including catalysis.

Silica gels with well-defined co-continuous gel skeletons and pore in the micrometer range have been prepared using a poly(ethylene oxide–propylene oxide–ethylene oxide (EO–PO–EO)) triblock copolymer. Being essentially independent of the micrometer-range structure, the mesopore exhibited narrow distributions around an identical median size and its volume was correlated well to the concentration of triblock copolymer. Small-angle neutron scattering of wet, dried and heat-treated gels revealed that the mesopore structure had been already templated at the sol–gel transition, and was preserved or even enhanced during the removal of solvent and carbonaceous constituents.

Influences of casting solvent on the microphase-separated structures of poly(2-vinylpyridine)-block-polyisoprene films were studied by transmission electron microscopy and small-angle X-ray scattering. The variations of the structures obtained were consequences of vitrification of microdomain structures developed during the solvent casting processes. The various microphase-separated structures were properly understood by considering the Hansen's solubility parameters of the solvent and the copolymer, which quantify the polymer–solvent interactions in the system.

Self-assembled structures in solvent-cast mixtures of polystyrene-block-poly(ethylenepropylene) (PS−PEP) and polystyrene-block-(partially hydrogenated polyisoprene) (PS−HPI) were investigated by small-angle X-ray scattering and transmission electron microscopy. Various self-assembled structures were observed in the solution-cast films, depending upon the degree of hydrogenation of the HPI block of the PS−HPI. The microdomain structure of PS domains and domains composed of PEP and HPI (called “rubber domains” hereafter) was first formed at relatively low polymer concentrations during the solvent-casting process over the whole range of the hydrogenation in our experiments. Subsequently, at a higher concentration during the process, phase separation between PEP and HPI in the rubber domains was observed in mixtures with medium and high hydrogenation. For mixtures with low hydrogenation, repulsive interactions between PEP and HPI become large enough to cause the segregation between PEP and HPI, which leads fi...

(2成分) ブロック共重合体において, その分子内組成が34～38%程度であるときに出現すると報告されている規則的共連続ミクロドメイン構造に注目する. 規則的共連続構造は, 周期的極小曲面を基礎として議論されることが多く, また, 観察手法として透過型電子顕微鏡がよく用いられる. しかし, 構造の複雑さのために, 得られた顕微鏡像が多数ある周期的極小曲面のどれに帰属するかを判断することは困難を極める. 筆者らは, いくつかの異なる周期的極小曲面に基づく共連続構造のモデルについて, その界面曲率 (分布) を測定した. その結果, 界面曲率は各モデルに特徴的な分布形状を示すことがわかった. このことは, 実験によりブロック共重合体の規則的共連続構造の界面曲率分布を求めることができれば, もととなる周期的極小曲面の同定が可能であることを示唆している.

ポリマーアロイの構造解析研究の新しい潮流として, 三次元画像解析および三次元構造定量解析を提案する. 高分子多成分系の最も単純な系である高分子二成分混合系を取り上げ, この系の相分離過程で形成される構造の微分幾何学的な特徴について考察した. 従来の研究の多くは, 相分離構造の粗大化過程を, 周期長に代表される相分離構造のおおまかな (globalな) 特徴を記述するパラメーターでとらえてきた. 界面の形態などの局所的な構造とその時間発展に関する研究例はごくわずかである. しかし, 異種の高分子がお互いの接触を避けるために界面を減らすことが相分離の駆動力であることを考慮すると, むしろ, 局所的な界面の形態とその時間変化こそが相分離の本質であろう. 本研究では, 界面の形態を共焦点レーザースキャン顕微鏡法により三次元実空間観察を行い, 界面曲率分布を測定する手法を開発した. 解析の結果, 高分子混合系の界面は双曲面からなることを初めて明らかにした. また, 界面曲率分布の時間変化を解析することにより, 界面という局所的な構造もスピノーダル分解後期過程において自己相似性をもつことも明らかとなった. さらに, 今後, 三次元構造解析によって測定可能となるであろう新しい構造パラメーターとそれらを用いた構造解析研究の可能性について述べる.

Directed self-assembly processes of polymeric systems represent a powerful approach for the generation of structural hierarchy in analogy to biological systems. Herein, we utilize triiodide as a strongly polarizable counterion to induce hierarchical self-assembly of an ABC miktoarm star terpolymer comprising a polybutadiene (PB), a poly(tert-butyl methacrylate) (PtBMA), and a poly(N-methyl-2-vinylpyridinium) (P2VPq) segment. Hereby, the miktoarm architecture in conjunction with an increasing ratio of triiodide versus iodide counterions allows for a stepwise assembly of spherical micelles as initial building blocks into cylindrical structures and superstructures thereof. Finally, micrometer-sized multicompartment particles with a periodic lamellar fine structure are observed, for which we introduce the term "woodlouse". The counterion-mediated decrease in hydrophilicity of the corona-forming P2VPq block is the underlying trigger to induce this hierarchical structure formation. All individual steps and the corresponding intermediates toward these well-defined superstructures were intensively studied by scattering and electron microscopic techniques, including transmission electron microtomography.