Abstract A mean field model is used to interpret the results of the spin labelling method and electron paramagnetic resonance on the conformations of polymers laying on a solid surface. Usually two different environments are detected namely trains tumbling slowly on the solid and loops and tails moving fast in solution. In evaluating these two parts it is possible to have a picture of the molecular state of the chains, flat or extended. The measured points are consistent with a cooperative character of the adsorption process. The model is modified in order to include that aspect.