SUPER TOUGH GELS WITH A DOUBLE NETWORK STRUCTURE

 Living tissues work with fantastic functions in soft and wet gel-like state. Thus, hydrogels have attracted much attention as excellent soft & wet materials, suitable for making artificial organs for medical treatments.However, conventional hydrogels are mechanically too weak for practical uses. We have created double network (DN) hydrogels with extremely high mechanical strength in order to overcome this problem. DN gels are interpenetrating network (IPN) hydrogels consisting of rigid polyelectrolyte and soft neutral polymer. Their excellent mechanical properties cannot be explained by the standard fracture theories. In this paper, we discuss about the toughening mechanism of DN gels in accordance with their characteristic behavior, such as large hysteresis and necking phenomenon. We also describe the results on tissue engineering application of DN gels.     

Fascicularones H–K,Four New Sesquiterpenoids from the Cultured Mycelia of the Fungus Hypholoma fasciculare

The AcOEt extract of Hypholoma fasciculare yielded four new congeners, fascicularones H ( 4 ), I ( 5 ), J ( 6 ), and K ( 7 ). All structures were unambiguously established by 1D and 2D NMR and MS data. In a lettuce seedling assay, compounds 4 – 7 showed radicle elongation.     

Explosion hazards of ion exchange resin mixed with perchloric acid

On January 21, 2003, an explosion occurred while ion exchange resin (IER) was being used to separate impurities from uranium solution. To clarify the cause of the accident and go/no-go criteria of the explosion, elemental analysis of the IER, DSC analysis, and SIKAREX analysis (a screening tool for runaway reactions) were performed. Finally, experiments on the same scale as the accident were conducted in an explosion chamber. When HClO₄ was added to IER-NO₃, the IER violently exploded without any heating nor metal ions such as uranium. It was confirmed that the accident was caused by an incorrect procedure in the chemical process. From the standpoint of explosion safety, IER-NO₃ in particular should be kept away from perchloric acid in the laboratory.     

Theoretical study of the mechanism of valence tautomerism in cobalt complexes

Valence tautomerism is studied in the [Co(II-HS)(sq)(2)(bpy)]/[Co(III-LS)(sq)(cat)(bpy)] mononuclear cobalt complex by using DFT methods (HS, high spin; LS, low spin; cat, catecholate; sq, semiquinone; bpy, 2,2'-bipyridine). Calculations at the B3LYP* level of theory reproduce well the energy gap between the Co(II-HS) and Co(III-LS) forms giving an energy gap of 4.4 kcal/mol, which is comparable to the experimental value of 8.9 kcal/mol. Potential energy surfaces and crossing seams of the electronic states of the doublet, quartet, and sextet spin states are calculated along minimum energy paths connecting the energy minima corresponding to the different spin states. The calculated minimum energy crossing points (MECPs) are located at 8.8 kcal/mol in the doublet/sextet surfaces, at 10.2 kcal/mol in the doublet/quartet surfaces, and at 8.4 kcal/mol in the quartet/sextet surfaces relative to the doublet ground state. Considering the energy of the three spin states and the crossing points, the one-step relaxation mechanism between the Co(II-HS) and Co(III-LS) forms is the most probable. This research shows that mapping MECPs can be a useful strategy to analyze the potential energy surfaces of systems with complex deformation modes.     

水溶性导电高分子聚噻吩及其水凝胶的掺杂行为研究

用碘和高氯酸作掺杂剂对水溶性导电高分子聚（3-羧甲基噻吩）及其水凝胶的掺杂行为进行了系统研究。结果发现水溶胀聚（3-羧甲基噻吩）凝胶及其高分子很容易被高氯酸或碘的水溶液进行掺杂，且其掺杂能力强烈依赖于掺杂剂溶液浓度。对碘掺杂的高分子溶液，其掺杂过程不很稳定同时伴随着脱掺杂过程的发生，而对于聚噻吩凝胶，高氯酸极易使其掺杂，而且一旦掺杂则在掺杂状态下具有相对的稳定性。     

Deformation and molecular orientation in films of metallocene polypropylene,ethylene–butylene rubber,and their 80/20 (w/w) blend revealed by the simultaneous kinetic measurement of microscopic infrared dichroism,macroscopic stress,and mesoscale strain

Simultaneous kinetic measurement of microscopic infrared dichroism, macroscopic stress, and mesoscale strain was used to study the deformation mechanisms of metallocene polypropylene (MPP), ethylene–butylene rubber (EBR), and their blend (MPP/EBR = 80/20 w/w). As with pure MPP, the molecular orientation in the blend is dominated by the necking of the isotactic polypropylene matrix. During the necking passage through the mesoscale sampling area, the molecular orientation of the polypropylene matrix in the blend is smaller than that in the pure polypropylene film at the same level of mesoscale strain. However, the orientation of the EBR dispersed phase in the blend is larger than that in the pure EBR film. This may result from the partial miscibility of the two ingredients in the amorphous phases and their resultant strong interfacial interaction. The large stress supported by the MPP matrix extends to the island of the EBR domain and leads to its large deformation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1520–1531, 2005     

Free-vibration acoustic resonance of a nonlinear elastic bar

Free-vibration acoustic resonance of a one-dimensional nonlinear elastic bar was investigated by direct analysis in the calculus of variations. The Lagrangian density of the bar includes a cubic term of the deformation gradient, which is responsible for both geometric and constitutive nonlinearities. By expanding the deformation function into a complex Fourier series, we derived the action integral in an analytic form and evaluated its stationary conditions numerically with the Ritz method for the first three resonant vibration modes. This revealed that the bar shows the following prominent nonlinear features: (i) amplitude dependence of the resonance frequency; (ii) symmetry breaking in the vibration pattern; and (iii) excitation of the high-frequency mode around nodal-like points. Stability of the resonant vibrations was also addressed in terms of a convex condition on the strain energy density.