Dynamic nanofishing of single polymer chains

Single molecule force spectroscopy (SMFS) realized by atomic force microscope (AFM) on a single polymer chain (static nanofishing), where a polymer chain is picked up and pulled at its chemically modified terminals, only gives structural information such as persistence length and contour length. Beyond this technique, dynamic nanofishing, where an AFM cantilever is imposed on the forced oscillation at its resonant frequency (∼l10 kHz), enables us to investigate more fruitful information. The method gave extension-dependent changes of entropic elasticity and frictional coefficient with solvent molecules for mono-disperse living-polymerized polystyrene (PS). The solvent temperature dependence revealed that the frictional coefficient could be correlated with macroscopic "intrinsic viscosity." Another novel technique, nanofishing at fast pulling rate (fast nanofishing), exhibited internal entanglement of a single PS chain and its subsequent relaxation.