Instantaneous distributions are a convenient method to describe the microstructure of polymers in great detail and at low computational effort. They represent molecular architectural details such as the distribution of chain length or molecular weight, chemical composition, and long chain branching with elegant analytical expressions. As the name indicates, these distributions provide a “snapshot’” of the polymer microstructure at a given instant in time.
João B. P. Soares (University of Alberta) in his Feature Article shows how the method of instantaneous distributions can be used to model the microstructures of polymers made under different polymerization conditions. The three main distributions investigated are the distributions of chain length (CLD), chemical or comonomer composition (CCD), and long chain branching (LCBD). It is also explained how the method of instantaneous distributions can be combined with reactor models to calculate the cumulative distribution of polymers made in reactors having different residence time distributions, spatial and time gradients.
Finally, the usefulness of this mathematical modeling technique is illustrated in several case studies involving olefin polymerization. Extensions for free-radical polymerization are also covered.