Single polymer chain rubber elasticity investigated by atomic force microscopy

A method, which is called as 'nanofishing', enabled us to stretch a single polymer chain adsorbed on an Au(111) substrate with picking it at its two thiol-modified termini using atomic force microscope equipped with a gold-coated probe. A force-extension curve obtained for a single polystyrene chain in a Θ solvent (cyclohexane) showed a good agreement with a so-called worm-like chain model, and thus gave microscopic information about entropic elasticity. Solvent effects on the statistical properties of single polymer chains were also investigated. For example, the second virial coefficient in cyclohexane was determined at a single polymer basis, which was almost comparable with a simple Flory's lattice model.