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Inspired by the structure of the cornea, which is the transparent front part of the eye, we developed a transparent and tough silica composite elastomer consisting of poly[di(ethylene glycol)methyl...

Here we demonstrate a simple, yet powerful method, atomic force microscopy (AFM) nanomechanical mapping, to directly visualize the interdiffusion and microstructure at the interface between two polymers. Nanomechanical measurements on the interface between poly(vinyl chloride) (PVC) and poly(caprolactone) (PCL) allow quantification of diffusion kinetics, observation of microstructure, and evaluation of mechanical properties of the interdiffusion regions. These results suggest that nanomechanical mapping of interdiffusion enables the quantification of diffusion with high resolution over large distances without the need of labeling and the assessment of mechanical property changes resulting from the interdiffusion.

The nanomechanical properties of polymers are sensitively affected by subtle differences in molecular structures. When the modulus of high-density polyethylene (HDPE) was measured with an atomic fo...

The topology of polymers affects their characteristic features, i.e., their microscopic structure and macroscopic properties. However, the topology of a polymer is usually fixed during the construction of the polymer chain and cannot be transformed after its determination during the synthesis. In this study, topology-transformable block copolymers that are connected via rotaxane linkages are introduced. We will present systems in which the topology transformation of block copolymers changes their 1) microphase-separated structures and 2) macroscopic mechanical properties. The combination of a rotaxane structure at the junction point and block copolymers that spontaneously form microphase-separated structures in the bulk provides access to systems that cannot be attained using conventional covalent bonds., The topology of a polymer is normally a fixed property of the material, derived from the characteristic of the monomers and their linkages. Here the authors present a method to transform the topology of block copolymers containing rotaxane linkages via acetylation.

Molecular aggregates were discovered in 1930’s, yet, the forces and excitonic coupling energy associated with the aggregate formation have not been detected so far. We directly measure such force and energy on single chains of the conjugated polymer polyfluorene using atomic force and fluorescence microscopes. The polyfluorene chain is attached on either side to a substrate and an AFM tip, respectively, and mechanically stretched under intense laser irradiation. The force – extension curves show force peaks that are attributed to gradual unfolding of the chain. Upon the irradiation, neighboring conjugated segments interact via excitonic coupling when in contact and experience an attractive force which is detected by the AFM. Analysis of the force curves provides excitonic coupling energy which is of same order as theoretically calculated values for a face-to-face fluorene dimer, and in agreement with the energy obtained from single-chain fluorescence spectra. Apart from contributing an essential piece of knowledge in the field of molecular photophysics, the work demonstrates on molecular scale a novel energy conversion mechanism from light to mechanical energy which could be potentially used, e.g., as a driving mechanism for molecular motors.

In single‐molecule force spectroscopy (SMFS), many studies have focused on the elasticity and conformation of polymer chains, but little attention has been devoted to the dynamic properties of single polymer chains. In this study, we measured the energy dissipation and elastic properties of single polystyrene (PS) chains in toluene, methanol, and N,N‐dimethylformamide using a homemade piezo‐control and data acquisition system externally coupled to a commercial atomic force microscope (AFM), which provided more accurate information regarding the dynamic properties of the PS chains. We quantitatively measured the chain length‐dependent changes in the stiffness and viscosity of a single chain using a phenomenological model consistent with the theory of viscoelasticity for polymer chains in dilute solution. The effective viscosity of a polymer chain can be determined using the Kirkwood model, which is independent of the intrinsic viscosity of the solvent and dependent on the interaction between the polymer and solvent. The results indicated that the viscosity of a single PS chain is dominated by the interaction between the polymer and solvent. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1736–1743

Cell transplantation therapy provides a potential solution for treating skeletal muscle disorders, but cell survival after transplantation is poor. This limitation could be addressed by grafting donor cells onto biomaterials to protect them against harsh environments and processing, consequently improving cell viability in situ. Thus, we present here the fabrication of poly(lactic-co-glycolic acid) (PLGA) ultrathin ribbons with “canal-like” structures using a microfabrication technique to generate ribbons of aligned murine skeletal myoblasts (C2C12). We found that the ribbons functionalized with a solution of 3,4-dihydroxy-l-phenylalanine (DOPA) and then coated with poly-l-lysine (PLL) and fibronectin (FN) improve cell attachment and support the growth of C2C12. The viability of cells on the ribbons is evaluated following the syringe-handling steps of injection with different needle sizes. C2C12 cells readily adhere to the ribbon surface, proliferate over time, align (over 74%), maintain high viability (o...

AFM-based nanomechanical measurements are powerful tools for the characterization of polymer composites. However, a flat surface of the samples is usually required, which restricts the wide applications of nanomechanical measurements. In this work, the height-fluctuation induced systematic errors were investigated taking polystyrene beads as the model sample. Corrections were further made based on the assumption that the components of force and deformation parallel to the sample surface can be approximately ignored. Results show the deviations of force and deformation due to height-fluctuations can be well corrected by the proposed method. Moreover, the reliability of the corrected force curves was further verified in the calculation of the mechanical properties. Young's moduli value without height-gradient dependency can be obtained by applying both Johson-Kendall-Roberts (JKR) model and Derjaguin-Muller-Toporov (DMT) model. The correction method proposed in this work can broaden the applications of AFM-based nanomechanical measurements on polymers without strict restrictions on the surface flatness.

Thermoplastic elastomers (TPEs) may generate a residual strain after being stretched, which hinders their potential for use in high-performance materials. However, the mechanism of the residual strain formation has not been sufficiently elucidated thus far. Here, we used atomic force microscopy-based nanomechanical mapping to investigate a stretched TPE specimen consisting of poly(styrene-b-ethylene-co-butylene-b-styrene) with a content of 15 wt% styrene (SEBS-15). In the SEBS-15 polymer structure that maintained a strain of 0.5, hard-segmental (HS) amorphous domains aggregated by poly(styrene) segments deformed and became oriented parallel to the stretching direction, whereas soft-segmental rubbery domains aggregated by poly(ethylene-co-butylene) segments elongated, formed a stress network using the HS domains as junction points. Moreover, an in situ observation adopted for the stretched SEBS-15 revealed that HS domains therein underwent a relative displacement and partial separation that was influenced by the formed stress network, which was strongly related to the irreversible phenomena.

Atomic force microscopy (AFM) offers nanoscale mapping of materials’ properties. Especially, our modified AFM termed “nanorheological AFM” enables us to measure the accurate frequency-dependent storage and loss moduli and loss tangent over a sixth-order frequency range without any temperature control at nanoscale resolution. These dynamic properties obtained by nanorheological AFM can be compared with those using bulk dynamic mechanical analysis (DMA) measurements. In this paper, we applied this technique to silica-filled styrene–butadiene rubber (SBR) to investigate the nature of the interfacial rubber region existing between a rubber matrix and silica particles at different temperatures. The dynamics properties of the interfacial rubber region were different from those of matrix rubber regions. The master curve obtained by this technique perfectly coincided with that by bulk DMA. Furthermore, it was found that the behavior of bulk loss tangent could be predicted by the contributions from both matrix and...

Ultrathin polystyrene (PS) films ranging from 14 nm to 316 nm were measured by atomic force microscopy (AFM) based nanomechanical mapping. Both supported and freestanding films were investigated to estimate the possible effect of the substrate. The as prepared supported ultrathin PS films show evident increase of Young's moduli and heterogeneities when the film thickness is reduced to less than 40 nm, whereas no clear thickness dependence can be found for ultrathin films after annealing. Besides, as prepared freestanding PS films thinner than 40 nm also show increased Young's moduli as decrease of the film thickness. The observed increased Young's moduli could be associated with the nano-confined film and contact load of the hard cantilever probe, where the adjacent molecular chains are perturbed and form a mechanically confined phase at the probe/polymer interface. Moreover, since as prepared and annealed ultrathin PS films show different thickness dependence in Young's moduli, it implies residual stress, confinement state of polymer chains, chain conformation, etc., which can be changed by annealing, affect the observed contact stiffening.

We incorporated bovine serum albumin (BSA)-functionalized graphene in poly(ethylene glycol) diacrylate (PEG) hydrogels. The graphene alignment in PEG hydrogels was changed using dielectrophoresis (DEP) forces. Effect of graphene concentration (2.55 and 5.1 mg/mL) and alignment (vertical and horizontal) on electrical and mechanical properties of hybrid graphene-PEG gels was evaluated. In addition, the molecular interaction of BSA peptides with graphene in the presence and absence of an electric field was assessed. The incorporation of graphene in PEG improved mechanical properties of hybrid gels. Dielectrophoretically aligned graphene-PEG hydrogels showed an anisotropic electrical conductivity. Young's modulus of 5.1 mg/mL graphene-PEG was almost three times higher than that of pristine PEG. Viability and proliferation of mouse embryonic stem cells on graphene-PEG gels were comparable with control PEG hydrogels. Ab initio calculations showed longer peptides had higher binding affinity towards graphene and caused a change in dipole moment due to the presence of electric field. The electric field also expanded graphene and peptide chains, which confirms the graphene alignment using DEP forces. Hybrid aligned graphene-PEG hydrogels may serve as functional biomaterials to engineer biological tissues and fabricate biomedical devices.

AIMS Tocilizumab (TCZ), a humanized anti-interleukin-6 receptor monoclonal antibody, is used to treat rheumatic diseases. There is limited information about the administration of TCZ during lactation. The dried spot method, a simple technique for processing biological samples which involves placement of a drop of specimen onto filter paper, has been used in clinical pharmacology to determine various drug concentrations. This study examined the feasibility of sample collection using the dried milk spot (DMS) method for obtaining data about the transfer of TCZ into breast milk. METHODS Concentrations of TCZ determined using DMSs prepared by patients were compared with those using liquid breast milk. RESULTS In an enzyme-linked immunosorbent assay of TCZ in DMSs, the accuracy ranged from 93.0% to 113.8% and the precision ranged from 0.3% to 8.4%. All concentrations of TCZ were within 15% of the reference value when analyzed on separate days. TCZ in DMSs at room temperature, 4°C, and -20°C were stable for 28 days. Extracted TCZ concentrations from patient-prepared DMSs were strongly correlated with those of liquid samples (r = 0.996). In a pharmacokinetic study, the median (range) maximum and minimum concentrations were 113 ng/mL (68-205) and 8.5 ng/mL (4.8-13.4), respectively. The milk-to-serum ratio at the trough TCZ concentration of 3 lactating mothers were 0.0015, 0.00082 and 0.0014. CONCLUSIONS The DMS method for measuring TCZ transfer into breast milk may be reliable and feasible, and should contribute to evaluating the safety of breast-fed infants whose mothers receive TCZ during lactation.

Dissipated energy mapping in amplitude-modulation atomic force microscopy was employed to characterize the nanoscale heterogeneous behavior of the viscoelastic response at the surface of polystyrene (PS) films of different molecular weight and architecture. By using an ultra-sharp probe with tip radius of ~1 nm, we were able to visualize the viscoelastic heterogeneities at the free surface of all PS samples. While the length scale of these heterogeneities at the surface of linear PS films was measured to be ~2.2 nm nearly independent of the molecular weight, it was significantly increased to ~3.1 nm at the surface of four-arm star-shaped PS films. We also demonstrated that similar nanoscale heterogeneous features were not observed when using a common probe with tip radius of ~10 nm, thereby confirming the intrinsic nature of the observed viscoelastic heterogeneities with sizes on the order of a few nanometers at the surface of PS films. This result provides important insights into the fundamental role of the molecular architecture in controlling the heterogeneous dynamics and many associated physical properties of amorphous polymer surfaces.

The stiffness-related properties of glassy and rubbery polymer films can behave differently when confined at the nanometer scale. However, direct measurements of the glassy and rubbery modulus of nanometer-sized polymer films are still limited and the existing models for explaining the thickness dependence of the polymer modulus remain in significant disagreement. By means of nanomechanical mapping with an atomic force microscopy, we report a direct measurement of the glassy and rubbery modulus of nanometer-sized poly(vinyl acetate) (PVAc) films supported by substrates of different moduli: Si and poly(vinyl alcohol). At ∼15 °C below the bulk PVAc glass transition temperature ( T g ), the modulus of PVAc films is found to be independent of the thickness as thin as ∼10 nm. In contrast, the modulus of rubbery films measured at ∼20 °C above the T g significantly increases when the film thickness is reduced to less than 100 nm, irrespective of the substrate modulus. Such an increase becomes more dramatic near the rubbery plateau regime of PVAc films. Among existing models, we demonstrate that the theoretical framework suggesting an increasing separation between the α -relaxation, sub-Rouse modes and Rouse modes induced by nanoconfinement is more appropriate when describing our experimental observation.

Objectives: To assess the effects of tocilizumab on pregnancy outcomes in Japanese patients with rheumatic disease. Methods: Data from Chugai’s tocilizumab safety database (April 2005 to October 2014) were retrospectively analyzed to identify pregnancy outcomes in patients exposed to tocilizumab. Results: Data were available for 61 pregnancies exposed to tocilizumab, and outcomes were reported for 50 of those pregnancies. In 36 births, no congenital anomalies were identified; however, six neonatal abnormalities were reported: five cases of low birth weight (

Probe indentation techniques have been widely used to characterize the stiffness-related properties of polymeric materials over the past two decades. However, it still remains challenging to apply these methods for directly measuring the elastic modulus of nanometer-sized polymer films supported by stiff substrates, primarily due to the convolution between the polymer and substrate moduli. Here, we report on the influence of the probe size on the ability of these methods to directly quantify the elastic modulus of nanometer-sized polymer films supported by a stiff substrate. Particularly, we employ the nanomechanical mapping by atomic force microscopy (AFM) in combination with Johnson–Kendall–Roberts two-point method to measure the elastic modulus of Si-supported ultrathin poly(vinyl acetate) (PVAc) films of thickness ranging from 9 nm to 610 nm. For sharp AFM probes of ∼12 nm in radius, this combination allows us to directly measure the elastic modulus of the polymer films as thin as ∼18 nm without being affected by the stiff substrate. In contrast, larger probes of ∼150 nm in radius show an obvious substrate-induced enhancement in the modulus of PVAc films with thickness ∼100 nm, even when the indentation depth of the probe into the films is kept less than 2–3 nm.

Spatial coordination of cell orientation is of central importance in tissue/organ construction. In this study, we developed microfabricated poly(lactic-co-glycolic acid) (PLGA) nanoribbon sheets with unique structures, using spin-coating and micropatterning techniques, in order to generate a hierarchically assembled cellular structure consisting of murine skeletal myoblasts (C2C12). The nanoribbon sheets were composed of aligned PLGA nanoribbons in the center, and strips on four sides which take a role as bridges to connect and immobilize the aligned nanoribbons. Such unique structures facilitated the alignment of C2C12 cells into bilayer cell sheets, and cellular alignment was directed by the aligned direction of nanoribbons. The nanoribbon sheets also facilitated the construction of multilayer cell sheets with anisotropic (orthogonal) and isotropic (parallel) orientations. The enhanced expression of myogenic genes of C2C12 cells on the bilayer cell sheets demonstrated that the nanoribbons induced C2C12 cell differentiation into mature myoblasts. The micropatterned nanoribbon sheets may be a useful tool for directing cellular organization with defined alignment for regenerative medicine and drug screening applications.

Although the formation of dynamic heterogeneities in glass-forming materials is believed to play an essential role in determining their properties as the glass transition is approached, direct imaging of these heterogeneities remains a challenge. Here, we report on a direct observation of nanoscale dynamic heterogeneities and their time evolution over ~10(3) s on the surface of a glassy polymer, polystyrene (PS), using atomic force microscopy with a 1 nm radius tip. The length scale of these heterogeneities was measured to be ~2.1 nm and the lifetime was determined to be ~10(2) s, in agreement with the length and time scales of heterogeneous dynamics reported for bulk polymers around the glass transition. These results are consistent with the existence of a very thin liquid-like layer at the glassy polymer surface. The validity of the method is confirmed by comparing the properties of surface dynamics of neat and plasticized films.

The effect of preparation methods and processing conditions on morphology and mechanical properties of poly(styrene- b -ethylene- co -butylene- b -styrene) (SEBS) triblock copolymer were investigated with atomic force microscopy (AFM) tapping mode and nanomechanical mapping, tensile testing, and gel permeation chromatograph (GPC). It was found that the samples prepared by solution casting and melt processing show large difference in morphology and mechanical properties. High shear rate does not induce alignment of lamellar block copolymer melts but leads to serious degradation of SEBS. As increase of rotational speed from 0 to 400 rpm, the molecular weight including M n and M w decreases from 67,100 to 26,000 and 70,000 to 43,000, respectively. Such large molecular weight decrease causes greatly decreased tensil strength but there is almost no evident effect on the well-phase separated morphology and Young's modulus of the SEBS. The Young's modulus distribution revealed by nanomechanical mapping becomes narrow as the increase of rotational speed. The amount of SEBS molecular having higher Young's modulus, which play a very important role in tensile strength of SEBS, also decreases.

The surface morphology and nanomechanical properties of poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) having different compositions were investigated using nanomechanical mapping measurements based on atomic force microscopy. We obtained the deformation image, true surface morphology, high-resolution Young’s modulus map, and map of deviated work simultaneously in a force mapping. Such maps were successfully used to identify and characterize the composition and better understand the relationship between microstructure and properties of SEBS samples. It is found that the obtained Young’s modulus and deformation values, both for polystyrene (PS) or poly(ethylene-co-butylene) (PEB) blocks, strongly depend on the microstructure that is dominated by the composition. As the PS composition increase, the modulus of PS blocks increases from 19.2 ± 2.5 MPa for SEBS (10/80/10) to 823.0 ± 168.1 MPa for SEBS (33.5/33/33.5), while PEB’s increases from 8.7 ± 2.1 MPa for SEBS (10/80/10) to 97.6 ± 17.8 MPa for SEBS...

A developed nanomechanical analysis of atomic force microscopy (AFM) based on the JKR theory has been applied to butyl rubber; isoprene-co-isobutylene rubber (IIR, butyl rubber). The force–deformat...

The linear thermal expansion coefficients (CLTEs) along flow direction (FD) for the injection-molded blends composed of isotactic polypropylene (iPP) and various ethylenic thermoplastic elastomers (TPEs) were investigated using a thermo-mechanical analyzer. The iPP/TPE blends with higher comonomer contents in the TPE showed extremely low CLTE. TEM observation revealed that the array of the TPE whose MFR was adjusted to be higher than the iPP matrix was in lamella-like sheet stacked normal to normal direction (ND) with being elongated along both FD and transverse-to-flow direction. At higher magnification of TEM, the iPP lamellae in the blend with higher comonomer contents in the TPE deeply penetrated into the TPE phase as a consequence of the faster iPP crystallization before the completion of the phase-separation. Hence, the location of the iPP amorphous chains would change depending on the comonomer contents in the TPE; in the case of the iPP/TPE blend with higher comonomer contents, large amount of the iPP amorphous chains would be trapped inside the TPE phase because of incomplete phase-separation arrested by faster crystallization. Therefore, the extremely low CLTE for the iPP/TPE blend with higher comonomer contents was accounted for by the simultaneous suppression of the thermal expansions from both the TPE phase and the iPP amorphous chains trapped inside the TPE by rigid iPP crystalline lamellae connecting in parallel with the TPE phase. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Oxide heterostructures with the broken translational symmetry often trigger a two-dimensional quantum confinement and associated unique electronic properties that cannot be observed in bulk constituents. Particular interest is devoted to the formation of two-dimensional electron gas (2DEG) at heterointerfaces between two insulators, which offers a fertile ground for fabricating advanced electronic devices. Here, we combine atomic force microscopy, transmission electron microscopy, and atomistic first-principles calculations to demonstrate that the (100) BiFeO3/SrTiO3 interface takes on a metallic nature and a 2DEG is generated at this interface. Our findings also reveal that the electronic reconstruction due to the polar discontinuity and the variation in valence state of Ti arising from diffusion of Ti cations in SrTiO3 to Fe sites of BiFeO3 are critical to the formation of 2DEG at the heterointerface.

A method, which is called as ‘nanofishing’, enabled us to stretch a single polymer chain adsorbed on an Au(111) substrate with picking it at its two thiol-modified termini using atomic force microscope equipped with a gold-coated probe. A force–extension curve obtained for a single polystyrene chain in a Θ solvent (cyclohexane) showed a good agreement with a so-called worm-like chain model, and thus gave microscopic information about entropic elasticity. Solvent effects on the statistical properties of single polymer chains were also investigated. For example, the second virial coefficient in cyclohexane was determined at a single polymer basis, which was almost comparable with a simple Flory's lattice model.

Two parts of the physics of rubber elasticity have not been fully verified experimentally to date. The first one is the entropic elasticity of a single polymer chain. The second one is Affine deformation hypothesis, the bridge between molecular bases of rubber elasticity and phenomenological deformation mechanics of polymer chain network. Atomic force microscopy (AFM) was employed to find a cue to experimental evidence for them. Therefore, we did not give much attention to AFM's high-resolution feature, while its nanometer-scale palpatbility was specially utilized instead. The technique, so-called, nanofishing revealed the entropic elasticity of a single polystyrene chain in good, or theta solvent conditions. The entanglement inside a single polymer chain was detected by nanometer-scale stress-relaxation experiment with quick stepwise strain excitation. The breakdown of Affine deformation was also observed in uniaxially elongated natural rubber vulcanizate, which showed a very wide modulus distribution. We concluded tentatively that the plateau region observed in macroscopic stress-strain curve could be attributed to the remaining of the local region that had sufficiently low modulus even after stretched at the elongation ratio of around 4.

A phase-separated structure of the injection-molded isotactic polypropylene (iPP)/poly(ethylene-co-octene) (EOR) binary blend was studied in three-dimension (3D) by transmission electron microtomography (TEMT). Highly oriented EOR domains along both flow- (FD) and transverse-to-flow (TD) directions resulting in stacking lamella-sheet like structures to normal direction (ND) were confirmed. Some irregularities in morphology and intervals between the EOR sheets, and thickness heterogeneity of the sheets, were observed more frequently in the TD rather than in the FD. Using the 3D information obtained by the TEMT, we have tried to elucidate massive anisotropy in linear thermal expansion coefficient (CLTE) along the injection directions in this blend. We found that the CLTE anisotropy was well correlated with the lamella-like sheets arrays and their irregularities.

Epitaxial Sr(V x Cr y Ti 1-x-y )O 3 (0 < x + y ≤ 0.05) ternary composition spreads were grown on two different single crystal substrates, LaAlO 3 and Nb-doped SrTiO 3 , by use of combinatorial laser molecular beam epitaxy with a specially patterned slide masking plate. The photocatalytic activity on the composition spreads was evaluated by the photo-reduction of Ag + in an AgNO 3 aqueous solution to deposit Ag metal on the spreads. The V-doping effect was found to depend greatly on the substrate: the photodeposition of Ag was much enhanced in the composition region of SrV 0.05 Ti 0.95 O 3 only on the Nb-doped SrTiO 3 , but not on the LaAlO 3 and non-doped SrTiO 3 .

Nanotribological properties of polystyrene/poly(vinyl methyl ether) blend surface mainly at its melt state were investigated using frictional loop (FL) measurement by atomic force microscopy (AFM). The energy dissipation estimated from the area inside the FL showed each peak against both temperature and scan rate. Indentation depth profile against scan rate was simultaneously detected. The indentation was largely restricted above the scan rate where the dissipation energy curve had a peak. We could succeed in drawing both master curves for the energy dissipation and the indentation depth using the same shift factor aT. It was concluded that AFM is a powerful tool for evaluating the nanotribological properties of polymer melt.

Surfaces of polymer blends were investigated using atomic force microscopy (AFM) to study their nanomechanical properties (nanorheology). We were particularly interested in information obtained from force-distance curve methods on rubbery or melt state samples. In order to realize clear comparison, a rubbery sample, polyisobutylene (PIB), was blended with a glassy-state sample, polystyrene (PS). When PS/PIB blends were observed in contact-mode operation, PIB-rich phases appeared as depressions. However, this was an artifact caused by the very low elastic modulus of PIB. By analyzing the force-distance curve, sample deformation by the force exerted was estimated together with real height free from sample deformation. Thus, if force-distance curve measurements are performed on every point of the sample (force-volume measurements), we can reconstruct a “real height image” and a “sample deformation image.” The apparent depressions became almost flat in the “real height image” by this analysis. With further analysis using Hertz theory, an elastic modulus image of the sample was also obtained, which correlated more closely with the “real height image” than with the“apparent height image.”

In injection molded specimens consisting of isotactic polypropylene (iPP)/poly(ethylene-co-octene) (EOR) blends with different viscosity ratio of η(EOR)/η(iPP), the coefficient of linear thermal expansion (CLTE) was investigated by thermal mechanical analysis (TMA). It was found that the blend with a smaller viscosity ratio showed the larger anisotropy of CLTE depending upon the directions. TEM observations revealed that the shape of rubber domains varied from slabs, cylinders to ellipsoids in shape, by increasing η(EOR)/η(iPP). The crystal orientation analysis by WAXD have revealed that the blend with ‘slab’ EOR domains showed the orientation of the c-axis of iPP crystals was preferably oriented to FD (flow direction) and TD (transverse to FD), and that the b-axis was exclusively oriented to ND (thickness direction). The CLTE of each FD and TD was in good agreement with the rules-of-mixing for CLTE by introducing the effect of the arrays of the elastomer domains and the PP crystal orientation. On the other hand, the CLTE in ND showed massive discrepancy between the calculation and observation. It was found that the incorporation of the retraction effect could explain the discrepancy to some extent.

We have demonstrated high-throughput synthesis and screening of a thin film photocatalyst library. Pulsed laser deposition enables us to grow the thin film photocatalyst epitaxially with atomically flat terraces and steps. A binary composition spread of [(SrTiO3)1?x(LaAlO3)x] (0 < x < 1) was fabricated by a combinatorial composition gradient technique. To evaluate the photocatalytic activity for the composition spread, the photodecomposition of pentacene film on the spread was employed and was analysed quantitatively after UV illumination by using an atomic force microscope. For comparison, the photodeposition of Ag from aqueous silver nitrate solution (0.01 M) was also tested. The results obtained from the two methods were basically the same: the SrTiO3-rich region in the film showed greater photocatalytic activity.

We have recently investigated the structure and properties of biodegradable polymer based blends. The biodegradable polymers studied in our work include poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV), poly(butylene succinate) (PBSU), poly(ethylene succinate) (PES) and poly(e-caprolactone) (PCL). The miscibility, morphology, crystallization and melting behaviour of biodegradable polymer based blends have been studied extensively, which were reviewed briefly in this manuscript.

Structural control of titanium dioxide, TiO2, thin films was achieved by the selection of appropriate substrates. The rutile phase of the TiO2 thin film was grown on α-Al2O3(0 0 0 1) substrate, while the anatase phase was on SrTiO3(0 0 1) and LaAlO3(0 0 1) substrates. The crystallinity of the anatase films has been much improved by the use of the LaAlO3(0 0 1) substrate. The combinatorial doping with 3d transition metals in the TiO2 thin films was carried out for the rutile and anatase films in much shorter time than the conventional one-by-one process, leading to the discovery of transparent ferromagnetism in the Co-doped anatase film.

Spatially and time-resolved optical emission analysis was carried out for the plasma plume produced by KrF excimer laser ablation of graphite in various oxygen atmospheres. Furthermore, highly ordered carbon nanofibers were fabricated by pulsed laser ablation using a graphite target containing approximately 1 mol.% metal oxide, such as NiO. In our laser ablation process, carbon nanofibers are deposited in an oxygen atmosphere. From the optical emission study, the visible carbon plasma plume in O 2 gas was found to be dominated by the emission of C 2 molecules and C atoms. Emission of a C 2 Swan band was strongly observed near the substrate under the diamond growth conditions (0.1–0.15 torr O 2 ). From the time-resolved emission study, ablated carbon particles were estimated to have a high kinetic energy of approximately 10 eV.

The effective delayed neutron fraction βeff for a light water moderated low-enriched UO2 core has been re-evaluated to obtain benchmark data for the validation of calculation codes and nuclear data. Originally, the βeff value was measured by the substitution method. In that method, the βeff value was obtained from measured reactivity change by substituting a Sb-Cd-Pb absorber rod for a 2.6 wt% UO2 rod for all core regions. In the present evaluation, we have employed the latest value for the buckling coefficient of reactivity to re-evaluate the substitution reactivity with high accuracy. In addition, the correction factor, which was ignored in the previous measurement, has been calculated to compensate the difference in the absorption cross sections of fuel and absorber rods. Consequently, the obtained βeff value in the present evaluation was 0.00771±0.00017, and it is more credible than the previous one. The present result is available as benchmark data for the verification of delayed neutron data for lig...

Dimerized (tandemly repeated) protein was constructed, and the stretching force during the unfolding of the single protein molecule was measured using an atomic force microscope. In quasistatic measurements using normal force–distance curve measurements, each monomer unit was unfolded step by step. To elucidate the conformational state at each extension length, we measured the relax–stress response of the protein using short stroke sinusoidal movements of the sample stage. This allowed us to investigate the dynamic response of the protein repeatedly without full stretching or rupturing. Although the protein molecule responded in-phase to the applied movement in most cases, we found a novel out-of-phase response around the stretching length where the second monomer unit unfolded. Applying the spring constant measured in the quasistatic experiment, the out-of-phase response was reproduced in the simple calculation, which suggested the folding and the unfolding at the second monomer unit were taking place repeatedly during the relax–stress response measurement.

The crystallization behavior and morphology of poly(ϵ-caprolactone) (PCL)/poly(vinyl butyral) (PVB) blends containing carbon black (CB) were studied as functions of PVB and CB content. The presence of CB had no influence on the primary nucleation of PCL crystals or the spherulitic growth rate. They were only influenced by the blend ratio of PVB. The growth rates of spherulites were unchanged throughout the crystallization process, regardless of the CB content. The results indicate that the concentration of PCL at the front of growing spherulite remains constant during crystallization. The distribution of CB in the spherulites was observed using atomic force microscopy to explain these results. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 797–802, 1997

To investigate the accuracy of the neutronic calculations in various neutron spectra, the modified conversion ratios [(MCR): ratio of {sup 238}U capture rate-to-total fission rate] of four kinds of light water-moderated UO{sub 2} fuel lattices were measured. In the measurements, the relative reaction rates of {sup 238}U capture and total fission were obtained from the nondestructive gamma-ray spectrometry of {sup 239}Np and {sup 143}Ce, respectively, which accumulated in the fuel rod irradiated at the Tank-Type Critical Assembly. The moderator-to-fuel volume ratios V{sub m}/V{sub f} of the measured lattices were 1.50 (undermoderate) to 3.00 (overmoderate). The measured MCRs were 0.477 {+-} 0.014(V{sub m}/V{sub f} = 1.50), 0.434 {+-} 0.013(1.83), 0.383 {+-} 0.011(2.48), and 0.356 {+-} 0.011(3.00), respectively. The Monte Carlo calculation employing the JENDL-3 library showed good agreement with the experiments for all the cores, although they showed a tendency of overestimation for larger values of MCR, as shown in the case of UO{sub 2} tight lattices. Therefore, it was concluded that, for the cores investigated, the accuracy of the neutronic calculation method currently used was very good.

The mechanical properties of a single chain of a synthesized polystyrene were measured by atomic force microscopy (AFM). In the conventional force-distance curve measurement, the stress-strain behavior of a chain was obtained. We also measured the dynamic sinusoidal response, as in macroscopic rheological studies, repeatedly at several extension lengths before full stretching or rupturing, by a “nanorheology AFM” that we constructed. It enabled us to design any required movements on a z-piezoelectric scanner, especially sinusoidal movements. The rheological properties of a single polymer chain were discussed from the frequency-dependent measurement.

Structure and binding condition of thiophene self-assembled monolayers (SAMs) formed on Au(111) were investigated by using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The STM study revealed the first molecularly resolved image for closely packed thiophene SAMs having two domain structures: disordered phases near domain boundaries and ordered domains consisting of pairs of molecules separated from each other by 4.35 A, from the next row by 3.9 A, and from the next columns by 8.8 A. From the STM observation, it is considered that a cofacial interaction between thiophene molecules plays an important role in determining the surface structure of thiophene SAMs on Au(111). The XPS spectra in the S 2p region of thiophene SAMs on Au(111) were observed at 161 (S 2p3/2) and 162 eV (S 2p3/2), which are assigned to the gold-bound sulfur. In contrast to previous XPS and theoretical studies, our high-resolution STM and XPS measurements have clearly demonstrated that the sulfur headg...

A new strain of influenza A virus (novel influenza A H1N1) that originated in swine has rapidly spread from the initial outbreak in Mexico and the southern United States to Canada and many countries in Europe and Asia. Consequently, the World Health Organization raised the level of alert for an

The invention of atomic force microscopy (AFM) enabled us to study the statistical properties of single polymer chains by a method called "nanofishing," which stretches a single polymer chain adsorbed on a substrate with its one end by picking it at the other end. A force-extension curve obtained for a single polystyrene chain in a Theta solvent (cyclohexane) shows good agreement with a worm-like chain model and, therefore, gives microscopic information about entropic elasticity. Furthermore, the nanofishing technique can be used for dynamic viscoelastic measurement of single polymer chains. An AFM cantilever is mechanically oscillated at its resonant frequency during the stretching process. This technique enables the estimation of quantitative and simultaneous elongation-dependent changes of stiffness and viscosity of a single chain with the use of a phenomenological model. In this study, the effect of solvent on viscosity in low extension regions reveals that the viscosity is attributed to monomer-solvent friction. Thus, static and dynamic nanofishing techniques are shown to give powerful experimental proofs for several basic questions in polymer physics. The techniques are expected to reveal hidden properties of polymer chains or polymer solutions by any types of macroscopic measurements in the future.