EFFECT OF SOLVENT QUALITY ON THE RHEOLOGICAL AND RHEOOPTICAL PROPERTIES OF FLEXIBLE POLYMER-SOLUTIONS

The dynamics of dilute solutions of flexible polymer molecules with in tramolecular excluded volume interactions are modeled using nonequilib rium Brownian dynamics (NEBD) and configuration-biased Monte Carlo (CB MC) simulations. The mathematical model consists of beads interacting through stretching and excluded volume forces under both shear and ext ensional flow. Various conformational and rheological quantities, such as birefringence, mean squared end-to-end distance, and viscosities, are calculated for steady-state and transient flows, with the primary independent variable being the solvent quality e. The model predicts coil-stretch transitions in extensional flow. The molecular weight sca ling of the critical extension rate is found to vary as M-1.6 under po or solvent conditions and M-2 in a good solvent, in qualitative agreem ent with experiments reported in the literature. Model calculations al so qualitatively capture a number of other observed features, most not ably higher elongational viscosities under good solvent conditions and faster relaxation behavior under poor solvent conditions.