Steady uniaxial elongational flows: Roles of intramolecular potentials

We examine the roles of several types of intramolecular interactions in the behavior of the steady elongational flow properties of infinitely dilute polymer solutions. In particular, bond stretching bond bending, bond torsion, and nonbonded intramolecular interactions are included. Geometric and rheological properties are calculated using Monte Carlo integration. We observe that bond bending and nonbonded interactions result in significant changes over the traditional bond stretching predictions, but bond torsion plays only a minor role. Bond bending results in more abrupt chain expansion with increasing elongation rate, and the corresponding increase in the elongational viscosity is also more steep. Nonbonded interactions cause the chain to be more spheroidal at lower elongation rates, and they result in a minimum in the elongational viscosity at an intermediate elongation rate-presumably as a result of excluded-volume effects causing the chain to be slightly more expanded.