We review mechanical and fracture properties of gels and elastomers containing polyrotaxane, necklace-like supramolecular assembly in which axial polymer chain is threaded through ring molecules. By cross-linking ring molecules of different polyrotaxanes in solution, polymer chains are cross-linked by figure-of-eight cross-links and the obtained polymer networks are called slide-ring (SR) gels. The unique feature of SR gels is that the cross-linking points consisting of two rings can slide on polymer chains and chain length between cross-links changes with macroscopic deformation. From our crack propagation tests on SR gels with different structural parameters (cross-linking density, axial chain length, and ring coverage on polymer), we have found that the sliding of the movable cross-links enhances their mechanical toughness without any reduction of stiffness (Young's modulus). The slide-ring concept also can be applied to polymer gels and elastomers cross-linked by small amount of polyrotaxane cross-linkers.

Elastomer microspheres are soft and colloidally stable in aqueous solution. Generally, thin films are formed by evaporating water from the dispersions. The method has been applied to various industrial products such as painting, adhesives, and coating materials. However, latex films are brittle, and thus, many kinds of additives (e.g., surfactants) and/ or post polymerization modification are required to obtain mechanically stable latex films. Under such a back ground, we found that elastomer microspheres crosslinked with rotaxane can form tough latex films just by evaporating water without any additives and post polymerization modifications. In this present article, we report on the influence of annealing on the mechanical properties of our latex films.

In a previous study (Sakai A., et al., ACS Cent. Sci., 4, 477 (2018)), a spherical microgel of gelatin prepared inside a lipid droplet was reported to have a higher surface elasticity than the bulk gel. In this study, we investigate the role of contact or lack of contact between gelatin and the lipid membrane as well as the micrometric confinement to isolate the dominant cause of this higher elasticity of microgels. For our experiment, we prepared a concave microgel of gelatin with two surfaces, with one surface in contact with the lipid membrane and the other without being in contact with the membrane. Next, we measured the elasticities of both the surfaces by using micropipette aspiration. Although the elasticity of the surface not in contact with the lipid membrane was slightly lower than that of the surface in contact with the membrane, the elasticity value was much higher than that for the bulk gel. Further, it was found that the droplet confinement without lipids did not decrease the elasticity of gelatin microgels. These results demonstrate that the dominant factor responsible for the higher elasticity of gelatin microgels is micrometric confinement and not their contact with the lipid membrane.

Cluster growth process during the gelation is attractive from both scientific and biomedical point of views. Until now, there have been many attempts from theoretical and experimental approaches. However, the comparison of the experimen tal results with the theoretical prediction is ambiguous, because it is impossible to quench the gelation reaction and directly estimate the connectivity in experiments. In this study, we fabricated the states near the critical points using the Tetra-PEG gel system with off-stoichiometrically mixing. We estimated the connectivity directly using the NMR measurement. Using this system, we performed the DLS and viscosity measurements to discuss the cluster growth. The cluster size increase with approaching the gelation critical point showing the characteristic scaling relationship. The scaling exponent depended on the polymer concentration at preparation. At the high concentration region, the exponent agrees with the prediction of the percolation theory. While it downwardly deviates from the prediction in low concentration, which suggests the lattice approximation is failed below the overlapping concentration.

A process to produce the dichroic thin film by applying the chromonic liquid crystal, which is in the nematic phase, on the glass substrate is investigated. The influence of the drying process in the degree of orientation and homogeneity of the dry film is experimentally evaluated. During the drying process, the extinction suddenly increases at when the drying-front that is boundary of the wet and dry regions passes through the measurement point. The local drying time is defined by the time from the application of the thin film till the time when the drying-front passes at each local measurement point. We introduce a new evaluation method of the dichroism and the film thickness and evaluate their two-dimensional distribution on the dry film. In the case of the high concentration and high viscosity liquid, the dichroism is independent of the drying time. The thicker liquid film reduces the homogeneity and the dichroic property during the drying process. It means that the advection and the transport are caused and they disturb the aggregates orientation in the drying process. In order to produce the higher quality dichroic film, the higher viscous and thinner liquid film should be applicated to reduce the disturbance of the orientation in the drying process.

In this paper, the flow of blood through a curved vessel having stenosis and aneurysm is investigated. To evaluate the impact of stenosis and aneurysm in a curved channel, the curvilinear coordinates are used to formulate a suitable geometry. The flow and heat transfer are investigated in the presence of nanoparticles that play a significant role in blood flows through arteries and they are gaining popularity in hematological treatment. The dynamical behavior of blood flow is modeled by using Eyring-Powell fluid model and the coupled partial differential equations are formulated to study the blood rheology. The flow, and heat and mass transfer equations are numerically solved by using finite difference scheme. The effect of some significant parameters on blood flow through a curved channel with stenosis and aneurysm is discussed and displayed in graphs. The pattern of blood flow is also depicted through geometrical patterns.