Shintaro Nakagawa

We studied active flexion from 90° to 133° and passive flexion to 162° using MRI in 20 unloaded knees in Japanese subjects. Flexion over this arc is accompanied by backward movement of the medial femoral condyle of 4.0 mm and by backward movement laterally of 15 mm, i.e., by internal rotation of the tibia. At 162° the lateral femoral condyle lies posterior to the tibia.

The crystallization behavior and crystal orientation of poly(ε-caprolactone) (PCL) homopolymers and PCL blocks spatially confined in identical nanocylinders have been investigated using differential scanning calorimetry (DSC) and two-dimensional wide-angle X-ray diffraction (WAXD) as a function of cylinder diameter D. The PCL homopolymers confined in nanocylinders were prepared using microphase separation of PCL-block-polystyrene (PCL-b-PS) copolymers with a photocleavable o-nitrobenzyl group (O

This review provides comprehensive knowledge on synthetic methods of star polymer networks – structurally controlled three-dimensional networks of polymer chains by means of end-linking between monodisperse star polymers.

We investigated the microscopic structure of the nonswellable hydrogel using small-angle neutron scattering (SANS). The hydrogel consisted of four-armed thermoresponsive prepolymer units embedded in a homogeneous network of four-armed poly(ethylene glycol) (Tetra-PEG). The structure of the hydrogel was similar to that of the ordinary Tetra-PEG hydrogels at temperatures below 16.6 °C, whereas discrete spherical domains were formed at temperatures above 19.5 °C. The number of prepolymer units cont

The crystallization behavior of poly(ε-caprolactone) (PCL) chains (i.e., PCL block + PCL homopolymer systems) spatially confined in nanocylinders with different diameters D has been investigated as a function of the mole fraction of PCL homopolymers fhomo existing in the PCL chains. The nanocylinders with PCL chains inside were prepared using the microphase separation of PCL-block-polystyrene (PCL-b-PS) diblock copolymers with a photocleavable o-nitrobenzyl group (ONB) between PCL and PS blocks,

Elastomers are indispensable materials due to their flexible, stretchable, and elastic nature. However, the polymer network structure constituting an elastomer is generally inhomogeneous, limiting the performance of the material. Here, a highly stretchable elastomer with unprecedented strain-stiffening capability is developed based on a highly homogeneous network structure enabled by a module assembly strategy. The elastomer is synthesized by efficient end-linking of a star-shaped aliphatic poly

We have investigated the effects of chain-ends tethering at nanodomain interfaces on the crystallization behavior of poly(ε-caprolactone) (PCL) chains spatially confined in lamellar nanodomains. The PCL chains tethered at both chain-ends (T2-PCL), one chain-end (T1-PCL), and no chain-end (i.e., PCL homopolymers) (T0-PCL) were prepared from polystyrene-block-PCL-block-polystyrene (PS-b-PCL-b-PS) triblock copolymers having a photocleavable o-nitrobenzyl (ONB) group at either or both of block junct

A structurally controlled polymer gel was synthesized by end-linking a monodisperse star polymer in which each arm was a bottlebrush (BB) polymer densely grafted with side chains. The combination of atom transfer radical polymerization and postpolymerization modification yielded a four-arm star-shaped BB polymer with a controlled polymerization degree of the backbone and side chains. The reactive end groups introduced at the end of each arm reacted with small bifunctional linkers in solution, le

The microscopic structure of module-assembled thermoresponsive conetworks was systematically investigated as a function of both temperature T and the mole fraction of the thermoresponsive modules r using small-angle neutron scattering (SANS). The conetworks were prepared by end-linking of hydrophilic modules and LCST-type thermoresponsive modules in water by the molar ratio of (1 – r):r. When the hydrogels with 0.02 ≤ r ≤ 0.10 were heated above certain T, nanometer-scale spherical domains were f

Bottlebrush (BB) elastomers, in which load-bearing network strands are densely grafted with side chains, are gaining much attention due to their unique mechanical properties. Herein, we used <i>in situ</i> small-angle X-ray scattering coupled with tensile tests to investigate the microscopic structural changes induced in a model BB elastomer with a controlled network structure under uniaxial deformation. The model BB elastomer was synthesized by end-linking a monodisperse star-shaped BB polymer,

Precise control of the crystal orientation and hierarchical crystalline morphology is essential for application of crystalline polymers, although a homogeneous morphology with a controlled crystal orientation is rarely formed in polymer crystallization. Here we report the formation of a homogeneous surface morphology with submicrometer-scale periodicity by simple crystallization of polymer brushes on a solid substrate in poor solvents. Unlike the complex morphology commonly observed for crystall