Chemistry Agnostic and Facile Method for Programming the Molecular Weight Distribution of Polymers

Many of a polymer material’s bulk properties (e.g., tensile strength, viscosity, and self-assembly) are dependent upon its molecular weight distribution. Thus, optimizing the properties of polymers requires systematic tuning of their molecular weight distributions. We developed a simple protocol for the synthesis of polymers with precisely programmed molecular weight distributions, which is applicable across all polymerizations in which molecular weight increases with time. Experimentally, the solution from an active polymerization vessel is transferred to a quenching vessel over time, building a targeted molecular weight distribution. The transfer rate is calculated using a robust and versatile mathematical model. The model includes an interpolation method that predicts the molecular weight distribution at any time during polymerization from a limited set of kinetic data. This interpolation enables the predictive capabilities of our protocol. We demonstrate the method by synthesizing polymers with square or trapezoidal molecular weight distributions using the group transfer polymerization of methyl methacrylate, the ring-opening metathesis polymerization of exo-5-norbornene-2-methylbenzoate, the atom transfer radical polymerization of methyl methacrylate, and the ring-opening polymerization of butylene oxide.