Takamasa Sakai

As a new class of high-strength hydrogels, we designed a tetra-PEG gel by combining two symmetrical tetrahedron-like macromonomers of the same size. Because the nanostructural unit of the gel network was defined by the length of the tetrahedral PEG arm, the gel had a homogeneous structure and resultant high mechanical strength comparable to that of native articular cartilage. Furthermore, since the gel was formed by mixing two biocompatible macromonomer solutions, the gelation reaction itself an

After decades of efforts by many researchers, we have succeeded in realizing a near-ideal polymer network. This network, the Tetra network, is made by cross-end-coupling of tetra-arm polymer modules. The mechanical energy dissipation was extremely low (tan δ ≈ 10(-4) ). The macroscopic stress-strain relationship of the Tetra network was in good agreement with that of microscopic elastic blobs. The maximum breaking strength was extremely high (≥27 MPa). These results indicate that the Tetra netwo

Nanogel particles composed of the cross-linked copolymer of N-isopropylacrylamide and ruthenium catalyst for the Belousov−Zhabotinsky (BZ) reaction were prepared by emulsion polymerization. In the aqueous solution containing the BZ substrates, self-oscillation of gel beads on the nanometer scale was achieved. By comparing the oscillating behaviors of the conventional BZ solution, the linear polymer solution, and the suspension of gel beads, the polymerization effect and the cross-linking effect

Unlike hard materials such as metals and ceramics, rubbery materials can endure large deformations due to the large conformational degree of freedom of the cross-linked polymer network. However, the effect of the network's branching factor on the ultimate mechanical properties has not yet been clarified. This study shows that tri-branching, which entails the lowest branching factor, results in a large elastic deformation near the theoretical upper bound. This ideal elastic limit is realized by r

The Obukhov model is known as the model describing the dependence of the elastic modulus of polymer networks on the concentration and solvent class. In the Obukhov model, the Panyukov model, which assumed the Hooke's law of elasticity, was adopted for describing the elastic energy of a network strand. In this study, we for the first time extended both models from the semi-dilute to concentrated region to the dilute to semi-dilute region. To evaluate the extended model, we used Tetra-PEG gel, whi

Diffusion behavior of particles in hydrogels is important both for the fundamental understanding of mass transport and for practical applications and has been investigated for a long time. There are three major theories describing the diffusion behavior of small particles in a polymer network: obstruction, hydrodynamic, and free volume theories. Although many researchers have examined these three theories, their applicability is still unclear due to ambiguity stemming from the heterogeneity of c

A robust hydrogel with a reliable deformation region in an aqueous environment is proposed. The gel has a homogeneous network where hydrophilic/hydrophobic components are uniformly distributed. In an aqueous environment, aggregated hydrophobic segments serve as "mechanical fuse links," inhibiting sudden macroscopic fracture. The gel endures threefold stretching for more than 100 cycles in water without mechanical hysteresis.

Tetra-PEG gel, which is a polymer gel with a well-controlled network structure, was utilized to examine the model predicting the ultimate elongation ratio of elastomeric materials, i.e., the Kuhn model. The effect of polymer fraction, degree of polymerization of network strands, and connectivity of the Tetra-PEG gel was discussed. The ultimate elongation ratio was estimated from the stress-elongation curves using the extended Gent model. The ultimate elongation ratio of the Tetra-PEG gels with d