Collapse of Randomly Self-Interacting Polymers

We use complete enumeration and Monte Carlo techniques to study self-avoiding walks with random nearest-neighbor interactions described by v 0 q i q j , where q i = ± 1 is a quenched sequence of "charges" on the chain. For equal numbers of positive and negative charges ( N + = N - ), the polymer with v 0 > 0 undergoes a transition from self-avoiding behavior to a compact state at a temperature θ ≈ 1.2 v 0 . The collapse temperature θ( x ) decreases with the asymmetry x = | N + - N - |/( N + + N - ) and vanishes at x ≈ 0.6. For v 0 < 0, a θ-point is present at all x .