Multi-objective synthesis optimization and kinetics of a sustainable terpolymer

Jin Da Tan, Balamurugan Ramalingam, Kedar Hippalgaonkar

Abstract:

The properties of polymers are primarily influenced by their monomer constituents, functional groups, and
their mode of linkages. Copolymers, synthesized from multiple monomers, offer unique material properties
compared to their homopolymers. Optimizing the synthesis of terpolymers is a complex and laborintensive task due to variations in monomer reactivity and their compositional shifts throughout the
polymerization process. The present work focuses on synthesizing a new terpolymer from styrene,
myrcene, and dibutyl itaconate (DBI) monomers with the goal of achieving a high glass transition
temperature (Tg) in the resulting terpolymer. While the copolymerization of pairwise combinations of
styrene, myrcene, and DBI have been previously investigated, the terpolymerization of all three at once
remains unexplored. Terpolymers with monomers like styrene would provide high glass transition
temperatures as the resultant polymers exhibit a rigid glassy state at ambient temperatures. Conversely,
minimizing styrene incorporation also reduces reliance on petrochemical-derived monomer sources for
terpolymer synthesis, thus enhancing the sustainability of terpolymer usage. To balance the objectives of
maximizing Tg while minimizing styrene incorporation, we employ multi-objective Bayesian optimization
to efficiently sample in a design space comprising 5 experimental parameters. We perform two iterations
of optimization for a total of 89 terpolymers, reporting terpolymers with a Tg above ambient
temperature while retaining less than 50% styrene incorporation. This underscores the potential for
exploring and utilizing renewable monomers such as myrcene and DBI, to foster sustainability in polymer
synthesis. Additionally, the dataset enables the calculation of ternary reactivity ratios using a system of
ordinary differential equations based on the terminal model, providing valuable insights into the reactivity
of monomers in complex ternary systems compared to binary copolymer systems. This approach reveals
the nuanced kinetics of terpolymerization, further informing the synthesis of polymers with desired
properties