%0 Journal Article %T Heteropolymers in a Solvent at an Interface %A A. Maritan %A M. P. Riva %A A. Trovato %J Physics %D 1999 %I arXiv %X Exact bounds are obtained for the quenched free energy of a polymer with random hydrophobicities in the presence of an interface separating a polar from a non polar solvent. The polymer may be ideal or have steric self-interactions. The bounds allow to prove that a ``neutral'' random polymer is localized near the interface at any temperature, whereas a ``non-neutral'' chain is shown to undergo a delocalization transition at a finite temperature. These results are valid for a quite general a priori probability distribution for both independent and correlated hydrophobic charges. As a particular case we consider random AB-copolymers and confirm recent numerical studies. %U http://arxiv.org/abs/cond-mat/9901292v1