Chemistry Agnostic\nand Facile Method for Programming\nthe Molecular Weight Distribution of Polymers

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