2022 Annual Meeting
Towards Kinetic Modeling of Polyhydroxyurethane Solvolysis That Incorporates Polymer Topology and Morphology
Of the nearly 400 million tonnes of plastic waste generated yearly, polyurethanes (PUs) represent the largest class of polymers that is not yet commercially upcycled. Synthesis of PUs also requires the use of phosgene, an acutely toxic and increasingly regulated chemical. Polyhydroxyurethane (PHU), which is synthesized without phosgene, is a potentially safer alternative only differing from PU by an additional hydroxy group adjacent to the urethane linkage. Recycling of PU and PHU-like materials is challenging both because this class of polymers is defined by the urethane linkage rather than the specific monomer composition and because PUs are often used in a network topology, which cannot be melt-reprocessed due to these physical crosslinks. These challenges motivate the investigation of depolymerization methods, which allow the recovery of monomers that can be upcycled into new materials. Solvolysis has been identified as the most promising method of PHU depolymerization. Modeling work of this process is limited, however, and its complexity increases because monomer identity and polymer topology and morphology can influence solvolysis kinetics. While it can be difficult to capture this detail in a system of differential equations, Kinetic Monte Carlo (kMC) is a stochastic method of modeling reactions that allows tracking of structural and chain-specific detail such as weight-average molecular weight, gel point, and polymer topology and morphology. These features can then be incorporated into the kinetic model, providing predictions against which experimental data can be compared. A previous model uses a kMC approach to track PU topologies, while another tracks morphological characteristics during PET solvolysis. Here, we report our work developing a model which tracks both topology and morphology information for PHUs, building upon methods from these previous models.