Molecular dynamics simulations of reactive compatibilization of polymer blends are performed for a wide range of chain lengths and densities of reactive groups ρo. We directly observe the predicted diffusive growth as well as the saturation at later times. The crossover to the saturation regime is consistent with theoretical predictions. There is also a separate transition from second to first-order reaction kinetics. However, the crossover to first-order kinetics does not agree with predictions. Although a depletion layer builds up on a time scale ∝ ρo-2, we find that, for times less than the Rouse time τg, the copolymer per area is a function only of tρo3 for a wide range of ρo implying an additional crossover time scale which scales as ρo-3. The interface is unstable at later times for sufficiently large ρo. The surface tension vanishes before the interface roughens showing that the instability is initiated mainly by the vanishing surface tension. The time required for the surface tension to vanish scales as ρo-3. A dilute limit model is introduced to study the behavior for small ρo. In this limit, ∑(t) grows linearly with time asymptotically and the reaction rate is a slowly decreasing function of Z in agreement with theoretical predictions. For times less than τg there is a logarithmic correction to the linear growth.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry