  Based on the analogy with the quantum mechanics of a particle propagating in
a {\em complex} potential, we develop a field-theoretical description of the
statistical properties of a self-avoiding polymer chain in a random
environment. We show that the account of the non-Hermiticity of the quantum
Hamiltonian results in a qualitatively different structure of the effective
action, compared to previous studies. Applying the renormalisation group
analysis, we find a transition between the weak-disorder regime, where the
quenched randomness is irrelevant, and the strong-disorder regime, where the
polymer chain collapses. However, the fact that the renormalised interaction
constants and the chiral symmetry breaking regularisation parameter flow
towards strong coupling raises questions about the applicability of the
perturbative analysis.
