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Cholesteric liquid crystal elastomer (CLCE) films, whose helical axis is parallel to a direction in the film plane, exhibit a periodic surface undulation with a period corresponding to a half-pitch (about 100 μm) of the helical director configuration. Temperature variation drives not only a finite macroscopic uniaxial deformation along the helical axis but also a marked variation in the surface undulation. AFM results demonstrate that the surface undulation varies thermoreversibly like a stationary wave with an amplitude of about 600 nm. The top and bottom positions at 40 °C become the bottom and top ones, respectively, at 130 °C, while the undulation disappears near 100 °C. Microspectroscopy reveals the periodic spatial variation in optical birefringence, which reflects the quasi-helical superstructure of local directors in the CLCE films. The combined analysis of the results of AFM and microspectroscopy indicates that the thermally induced variation in the surface undulation becomes largest at positions...

We unequivocally verified a success of creating “voided double-gyroid-channel” morphology and identified for the first time its cleavage planes inherent in the morphology on the basis of computer analysis of field-emission scanning electron microscope (FE-SEM) images. This morphology was created by transforming the minor network phase of the double-gyroid cubic structure of block copolymers with Ia3d space group symmetry into empty space. The fabrication process leading to the morphology was proven to conserve the original double-gyroid structure. The FE-SEM images observed on the freeze-fractured surface of the morphology exhibited almost only two kinds of patterns: “periodic double-wave pattern” and “hexagonal doughnut pattern”. Thus, the images observed on the freeze-fractured surfaces are “deterministic”, compared with those observed under transmission electron microscopy on the ultrathin-sectioned specimens which essentially vary randomly, depending on the sectioning directions relative to the cubi...

A novel method was developed to measure the local curvatures of phase-separating interface, i.e., the mean and Gaussian curvatures, from three-dimensional (3D) digital images of the bicontinuous domain structures formed during a phase-separation process via spinodal decomposition (SD). One of the aims of the study is to quantify the local geometry of the interface and its time evolution. Distributions of the interfacial curvatures were obtained by calculating the curvatures at many points on the interface. The applicability and precision of the method were critically tested using various model surfaces, e.g., spheres, cylinders, ellipsoids of revolution, and an infinite periodic minimal surface (IPMS), Schoen's gyroid. The method was then applied to the 3D interface developed via SD of a polymer blend. It was found that the interface of the polymer blend (i) was, for the most part, hyperbolic and (ii) had a considerably broader curvature distribution than that of Schoen's gyroid, though area-averaged curv...

Three-dimensional (3D) macroporous morphology of a silica gel, formed as a result of the phase separation parallel to the sol−gel transition, was observed in real space by laser scanning confocal microscopy. The 3D image of the silica gel skeleton that was sintered into full dense pure silica glasses clearly demonstrated that the gel skeleton is continuous and interconnected in 3D space. The interface between the gel skeleton and the macropore was characterized in terms of interfacial curvatures. It was found that a large portion of the interface is hyperbolic, which is also found in a phase-separated structure of a binary polymer mixture developed during the spinodal decomposition (SD). Comparison was made in terms of the probability densities of the interfacial curvatures between the silica gel and a polymer mixture having an identical phase volume fraction to one of the phases. Although the probability density distribution of the mean curvature, H, representing geometrical characteristics of the interf...

The time-evolution of a three-dimensional (3D), bicontinuous interface of a phase-separated polymer mixture in the late stage spinodal decomposition (SD) process has been studied by laser scanning confocal microscopy (LSCM) and time-resolved light scattering. The time evolution of the interface between two coexisting phases developed via SD (“spinodal interface”) was quantitatively captured in 3D by using LSCM. On the basis of the differential geometry, probability densities of the local curvatures, i.e., the mean and Gaussian curvatures, of the spinodal interface have been experimentally evaluated. We found that a large portion of the interface formed in the late stage SD consists of a saddle-shaped surface, i.e., a hyperbolic surface. The probability densities were used to predict the dynamics of the spinodal interface. Two basic mechanisms are found to be important for the system to reduce interface area during the late stage SD. In addition, the probability densities of the curvatures at various times...

Internal structures of translucent poly(N-isopropylacrylamide) gel were for the first time observed by laser scanning confocal microscopy (LSCM). The observed image reflected the mesoscopic internal structures in the gel due to the “fixed concentration fluctuations” of network polymers as described in the text. Three-dimensional internal structures in the gel constructed from a series of the cross section images taken by the LSCM revealed that the gel had a bicontinuous domain structure consisting of regions dense and sparse in polymer networks.