## Abstract

The zero-shear-rate intrinsic viscosity of a flexible polymer confined in a slit in Couette and Poiseuille flow is investigated by Monte Carlo simulations of self-avoiding random walks on a simple cubic lattice and by analytical calculations in the free-draining limit. In the simulations an equilibrium ensemble of chains is generated and the intrinsic viscosities in Newtonian Couette and Poiseuille flows are calculated by Zimm's algorithm. The intrinsic viscosity is calculated with hydrodynamic interaction and for the free-draining limit. There is a striking difference between both flow types with respect to the influence of the slit width on the intrinsic viscosity. As shown before,7 the intrinsic viscosity in a Couette flow drops sharply from its unconfined value for distances between the plates for which the coils are squeezed. For a Poiseuille flow, on the other hand, the intrinsic viscosity starts to decrease gradually already at much larger distances. This difference is due to the fact that, due to the confinement, the polymers have a tendency to concentrate near the center of the slit, where in a Poiseuille flow the shear rate is 0. This occurs long before the real squeezing starts. In the limit of large slit widths the values coincide. These results are in agreement with analytical free-draining results and with calculations based on the Hookean dumbbell model of Goh et al.31,32

Original language | English |
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Pages (from-to) | 3695-3701 |

Number of pages | 7 |

Journal | Macromolecules |

Volume | 25 |

Issue number | 14 |

DOIs | |

Publication status | Published - 6-Jul-1992 |

## Keywords

- MOLECULARLY THIN-FILMS
- MONTE-CARLO METHOD
- NARROW CHANNEL
- SMALL PORES
- DYNAMICS
- MACROMOLECULES
- CHAINS
- SHEAR
- SLIT