Disorder induced adsorption of polymers

The competition between adsorption and entropic repulsion of a single self-avoiding polymer trapped in quenched media consisting of parallel, adsorbing rods distributed at random in the perpendicular plane are studied by simulations and analytical arguments. The chain undergoes an adsorption transition at finite temperature which is not observed in a regular medium. Below and above the transition temperature, the chain is essentially stretched parallel to the rods and shrunk in lateral directions with exponents ν ⊥ =0, v ∥ =1 for the corresponding components of the radius of gyration. These phenomena are based on two different mechanisms, localization by adsorption at low temperatures and localization by entropic repulsion at high temperatures. The present model is the first where the entropic localization occurs at arbitrary strength of self-avoidance. Analytical arguments suggest, in agreement with our data, that the chain obeys approximately conventional self-avoiding behavior at the critical adsorption temperature. We expect that both phenomena, disorder induced adsorption and entropic localization, can be tested experimentally