POLYMER-CHAIN IN A FLOW-THROUGH A POROUS-MEDIUM - A MONTE-CARLO SIMULATION

We study conformational and dynamic properties of dilute polymer solut ions drifting through a random environment of obstacles at varying int ensity of the external field B and of the host matrix density C-ob usi ng dynamic Monte Carlo simulation of an off-lattice bead-spring model. The presence of obstacles is found to influence strongly the conforma tional properties of the drifting chains: with growing strength of the field B and C-ob=0 the chain mean size (gyration radius), R-g(2), rap idly increases while the ratio between the end-to-end distance, R-ee(2 ) and R-g(2) drops essentially below the usual value of 6, typical in the absence of drift, suggesting a hooflike shape of the chain with bo th ends directed along the external field vector. We confirm the findi ng of G. M. Foo and R. B. Pandey [Phys. Rev. E 51, 5738 (1995)] of a c ritical strength of the external field Be above which the permeability of the host matrix sharply drops. A detailed study of this phenomenon suggests that B-c may be related to a dramatic growth of a specific ' 'capture'' time, characterizing the interaction of the chains with the obstacles, so that a simple model describing the drift of chains amon g obstacles may be shown to reproduce our findings.