  The elastic response is studied of a single flexible chain grafted on a rigid
plane and an ensemble of non-interacting tethered chains. It is demonstrated
that the entropic theory of rubber elasticity leads to conclusions that
disagree with experimental data. A modification of the conventional approach is
proposed, where the end-to-end distribution function (treated as the governing
parameter) is replaced by the average energy of a chain. It is revealed that
this refinement ensures an adequate description of the mechanical behavior of
flexible chains. Results of numerical simulation are compared with observations
on uniaxial compression of a layer of grafted chains, and an acceptable
agreement is shown between the model predictions and the experimental data.
Based on the analysis of combined compression and shear, a novel
micro-mechanism is proposed for the reduction of friction of polymer melts at
rigid walls.
