An integral equation study of percolation in systems of flexible and rigidmacromolecules

An earlier integral equation approach to percolation in macromolecular flui ds is extended to include attractive interactions between the sites represe nting flexible polymers. An analytic treatment based on the threadlike chai n model shows that the percolation threshold near the theta temperature is closely related to the usual semidilute overlap concentration, and is signi ficantly below the value found under athermal conditions. These results are consistent with the findings of numerical calculations on tangent-bead cha in models. The location of the static percolation threshold in the density- concentration plane with relation to the liquid-vapor spinodal boundary is investigated. Numerically obtained results for the percolation thresholds f or both flexible and rigid athermal, finite thickness, macromolecules are p resented, which are consistent with prior findings based on the analyticall y tractable threadlike chain model. (C) 2001 American Institute of Physics.