The Detachment of a Polymer Chain from a Weakly Adsorbing Surface Using an AFM Tip

Atomic force microscopy has been used to investigate the detachment of single polymer chains from surfaces and to measure the picoNewton forces required to extend the chain orthogonal to the surface. Such recent experiments show that the force−extension profiles provide interesting signatures which might be related to the progressive detachment of the chain from a surface. Using equilibrium scaling analysis, activation kinetics, and exactly solvable partition functions we predict force versus extension profiles for various extension rates. We also show how variation in the extension rate can distinguish heterogeneous monomer−surface contacts. The qualitative features that we predict, such as sawtooth force profiles with detachment forces which decrease with extension, maximal yielding forces at high extension rates, and featureless force profiles at large extension, are also seen in experiment.