THETA-POINT EXPONENT FOR POLYMER-CHAIN IN RANDOM-MEDIA

Using field-theoretic arguments for self-avoiding walks on dilute lattices with site occupation concentration p, we show that the θ-point size exponent θ{symbol}p0 of polymer chains remains unchanged for small disorder concentration (p>pc). At the percolation threshold p=pc, using a Flory-type approximation, we conjecture that θ{symbol}pc0=5/(dB+7), where dB is the percolation backbone dimension. It shows that the upper critical dimensionality for the θ-point transition at p=pc shifts to a dimension dc>3. We also propose that the θ-point varies practically linearly with p for 1>p≥pc. © 1990 Plenum Publishing Corporation.