Living organisms can move pliant and smoothly with extremely low frictional coefficients despite of that they have no bearing system. If the mechanism of low friction in the living organism is clarified, one can build up biomimetic machine systems. We have found that the frictional behaviors of hydrogel are totally different from those of soled materials exhibiting frictional coefficient as low as 10^-3.

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Stepwise assembly of structurally regulated synthetic polymers on the basis of stereocomplex formation was reviewed. Isotatic (it) poly (methyl methacrylate) (PMMA) and syndiotactic (st) PMMA were assembled by the stepwise immersion of a 9-MHz quartz-crystal microbalance (QCM) as a substrate into organic solutions at ambient temperature. Quantitative QCM analysis revealed that acetonitrile was the best solvent for assembly. The analysis also showed linear growth of the assembly, indicating that the amount of assembly can be easily regulated at each step. The ratios of st-/it-PMMA assembled, the static contact angle of the assembly at each step, and its reflection absorption spectrum (RAS) strongly implied the stepwise formation of a stereocomplex between it-and st-PMMAs in the assembly. Atomic force microscopic (AFM) observation of the assembly revealed a smooth surface. The assembly was formed at the step from the physically adsorbed it-PMMA to st-PMMA. A possible assembling mechanism was proposed. St-poly (ethyl methacrylate) and st-poly (propyl methacrylate) were also assembled with it-PMMA by stereocomplex formation from the same solvent system. St-poly (methacrylic acid) was assembled with it-PMMA from acetonitrile-mixed aqueous solvents. On the other hand, enantiomeric poly (lactide) s were similarly assembled on a QCM substrate, following immersion of QCM into alternating acetonitrile solutions. A quantitative QCM analysis at each step and a differential scanning calorimetric study of the assembly showed racemic crystal (stereocomplex) formation on the substrate surface. Atomic force microscopic observation showed a dotted nano-structure of the assembly.

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Amphiphilic polypeptides, poly (γ-methyl L-glutamate) containing β-cyclodextrin as active end group (PMG_n-CyD ; n=19, 24, 34) were prepared. The spectra of circular dichroism spectroscopy showed a-helical conformation of the PMG moiety. At the n-hexane/water interface, molecules of PMGn-CyD formed a stable monolayer. Interfacial pressure-area (π-A) isotherms suggested molecules of PMG_n-CyD to be oriented almost normal to the n-hexane/water interface. When α-helical rods were oriented almost normal to the interface, 2-P-tolidilnyl-naphtalene-6-sulfonate (TNS) added as a guest molecule for CyD to the water phase under the monolayer caused fluctuation in interfacial pressure. Periodic movement of the PMG_n-CyD monolayer due to the binding and release of guest molecules across the n-hexane/water interface was considered the reason for this.

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