Sequence randomness and polymer collapse transitions

Chain disorder with frustration can modify the universality class of scalin g at the theta transition of heteropolymers. This is shown for a model with random two-body potentials in 2D on the basis of exact enumeration and acc urate Monte Carlo results. When the average fraction of repulsive monomer-m onomer interactions grows beyond a certain finite threshold, the temperatur e below which disorder becomes relevant coincides with the theta one, and s caling exponents definitely start deviating from those valid For homopolyme rs.