Stretching of a polymer by an attractive wall

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Abstract
Using scaling arguments, we generalize to the excluded volume case an exact calculation that was made in a mean field calculation for the configuration of a polymer chain with one end fixed at a distance z from an adsorbing plane. In addition to the characteristic width of the adsorbed chain, there is a second distance that was ignored so far in subsequent discussions. This is the capture distance Z0 when the polymer starts being attracted by the surface: for larger distances the chain does not feel the surface. For smaller distances, if one end of the chain is fixed, a constant force has to be applied to keep it fixed and the polymer adopts a stretched configuration. We find Z0 ∼ Nδ2/3, where N is the length of the chain and δ the energy gain per monomer on the surface. We proceed by looking at the relaxation of such elongated chain when the constraint of fixed end is released. In this process, the chain relaxes the applied force by being sucked onto the surface. We find for the characteristic time for this process T ∼ N 2δ1/3. This may be relevant for extracting a chain from an adsorbed state. all our approach is based on Pincus' theory for a stretched polymer