Fundamental Research on New Type of Molecular Assemblies, "High-Density" Polymer Brushes

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Recent successful application of living radical polymerization made it possible to graft various low-polydispersity polymers with exceptionally high graft densities. In this study, the structure and properties of such obtained concentrated polymer brushes were systematically investigated in a swollen and dry state. The most striking result concerns their tribological properties in a good solvent : the frictional coefficient (μ) between concentrated PMMA brushes was dramatically lower than that between the semi-dilute brushes, which was reasonably ascribed to little interpenetration of swollen concentrated polymer brushes due to the large osmotic pressure and highly stretched conformation (entropic interaction). The obtained μ value is one of the lowest values comparable to that achieved for polyelectrolyte semi-dilute brushes with the help of a charge effect. This study would provide a new concept toward precision surface modification for "super" lubrication.