Molecular reorientation behavior of photocrosslinkable liquid-crystalline polymer films containing phenylamide side chains

The cooperative molecular reorientation in methacrylate copolymer films comprising photoreactive 4-(4-methoxycinnamoyloxy)biphenyl and phenylamide in their side chains was investigated by irradiation with linearly polarized ultraviolet light and subsequent annealing. Both cinnamate and phenylamide side groups were miscible in the copolymer composition, and axis-selective photoreaction of the cinnamate groups was observed. Thermally enhanced cooperative in-plane orientation of both side groups was obtained when the irradiated films were annealed in the liquid-crystalline temperature range of the copolymers.     

Local residual stress mitigation after curing process by spread fiber tow in carbon fiber-reinforced plastic

The application of the tow spreading technique to wound filaments or woven composites seems promising because of its advantageous strength enhancement mechanism. The effects of tow spreading on the curing progress and the residual stress of the resin were investigated in this study. We hypothesized that the homogeneous distribution of fibers realized by the tow spreading technique suppresses the stress concentration of the resin in the vicinity of close-packed fibers. This hypothesis was examined through finite element simulation using a micro-scale model with the definite separation of fiber and resin. The residual stress and strain after the curing process were investigated using a newly developed simulation system.     

Deformation Behavior Estimation of Aluminum Foam by X-ray CT Image-based Finite Element Analysis

Aluminum foam is a lightweight material owing to the existence of a large number of internal pores. The compressive properties and deformation behavior of aluminum foam are considered to be directly affected by the shape and distribution of these pores. In this study, we performed image-based finite element (FE) analyses of aluminum foam using X-ray computed tomography (CT) images and investigated the possibility of predicting its deformation behavior by comparing the results of FE analyses with those of actual compressive tests. We found that it was possible to create an analytic model reflecting the three-dimensional (3D) pore structure using image-based modeling based on X-ray CT images. The stress distribution obtained from image-based FE analysis correctly indicates the layer where deformation first occurs as observed in actual compressive tests. Also, by calculating the mean stress of each plane perpendicular to the direction of compression based on the stress distribution obtained from image-based FE analysis, it was found that deformation begins in the layer containing the plane with maximum stress. It was thus possible to estimate the layer where deformation begins during the compression of aluminum foam.     

Supramolecular nanodevices: from design validation to theranostic nanomedicine

The increasing importance of nanotechnology in the biomedical field and the recent progress of nanomedicines into clinical testing have spurred the development of even more sophisticated nanoscale drug carriers. Current nanocarriers can successfully target cells, release their cargo in response to stimuli, and selectively deliver drugs. More sophisticated nanoscale carriers should evolve into fully integrated vehicles with more complex capabilities. First, they should be able to sense targets inside the body and adapt their functions based on these targets. Such devices will also have processing capabilities, modulating their properties and functions in response to internal or external stimuli. Finally, they will direct their function to the aimed site through both subcellular targeting and delivery of loaded drugs. These nanoscale, multifunctional drug carriers are defined here as nanodevices. Through the integration of various imaging elements into their design, the nanodevices can be made visible, which is an essential feature for the validation. The visualization of nanodevices also facilitates their use in the clinic: clinicians can observe the effectiveness of the devices and gain insights into both the disease progression and the therapeutic response. Nanodevices with this dual diagnostic and therapeutic function are called theranostic nanodevices. In this Account, we describe various challenges to be overcome in the development of smart nanodevices based on supramolecular assemblies of engineered block copolymers. In particular, we focus on polymeric micelles. Polymeric micelles have recently received considerable attention as a promising vehicle for drug delivery, and researchers are currently investigating several micellar formulations in preclinical and clinical studies. By engineering the constituent block copolymers to produce polymeric micelles that integrate multiple smart functionalities, we and other researchers are developing nanodevices with favorable clinical properties.     

An electrochemical study of poly(2,2′-dithiodianiline) in acidic aqueous media

Poly(2,2′-dithiodianiline) [poly(DTDA)], which is a conducting polymer interconnected with disulfide (SS) bonds, was studied electrochemically in acidic aqueous media. Redox reactions and structural changes of the poly(DTDA) in acidic aqueous solutions at various applied potentials and pH values were investigated. A Pourbaix diagram [potential (E)-pH profile] for the poly(DTDA) was plotted in order to distinguish the structures of the poly(DTDA) for the applied potentials and the pH values. The detailed structural changes were characterized using in situ UV-vis and surface-enhanced Raman spectroscopies.     

Seasonal Variation of Microstructure and Sintered Strength of Dry-Pressed Alumina

An origin was investigated for the variation of the density and the fracture strength of sintered alumina with the manufacturing season. Direct observation using immersion microscopy was utilized to examine the microstructures of granules, green bodies, and sintered samples for two specific cases: samples made in summer and others made in winter. This method revealed a seasonal difference in the pore structure of both green and sintered bodies. The variation of the density and the fracture strength with the manufacturing season was ascribed to the different concentrations of large pore defects in sintered bodies, which were developed from the green body structures. Formation of large pore defects resulted from void spaces at the center and at the boundary of granules in the green bodies. High temperature and humidity contributed to an increase in the deformability of granules, reducing defect sizes in summer and thus improving fracture strength.     

Holographic recording in a photo-cross-linkable liquid crystalline copolymer using a 325-nm laser with various polarizations

Surface relief (SR) gratings with a molecularly oriented structure and pure polarization hologram were fabricated on a photo-cross-linkable liquid crystalline copolymer using a 325-nm laser with various two-beam polarization modes. For intensity holography, the polarization information from the two beams simultaneously provided the molecular motion and molecular reorientation; the SR height reached up to 186 nm and the concave area revealed a molecular reorientation when the exposing beams were linearly polarized. In contrast, SR formation was negligible for polarization holography when molecular reorientation due to the polarization modulation was observed. The resulting polarization gratings changed the polarization properties of the diffraction beams, and their diffraction efficiency was reached 24%, which agreed with theoretical expectations.     

Design of a highly ordered and uniform porous structure with multisized pores in film and particle forms using a template-driven self-assembly technique

A highly ordered arrangement of pores with multiple sizes in film and particle forms was successfully prepared using the dip-coating and spray-drying methods, respectively. The template-driven self-assembly technique was effective when a combination of 5 nm silica (as a model of an inorganic nanoparticle) and two different sizes of monodispersed polystyrene (PS) spheres (as models of the template) were self-assembled to produce a composite silica/PS template. Heat treatment was then used to remove the PS, which produced the porous particle. A material with spherical pores in an “art-design” organization was produced. The size of the pores (large pore: 100–1000 nm; small pore: 30–200 nm) could be controlled simply by adjusting the PS size. Sufficient numbers of large/small pores made it possible to produce a material of ultralow density with an ultralow refractive index, because the multiple pores allocated free space, all of which was confirmed by calculation.