We propose a simple friction model for isolated polymer chains on a solid s
ubstrate. The chains are pulled at constant velocity by one end, the other
end can be trapped on the solid substrate on localised sites. We focus on t
he energy dissipation due to the traps. This simple model leads to nontrivi
al friction laws, depending on the velocity and the distance between traps.
Some refinements of the model such as the effect of thermal fluctuations a
re also reported.