Polyurethane (PU) is the 6th most produced polymer, with a global market size of $37.8 billion in 2020. Unlike polyolefins, polyurethanes contain reactive C-O and C-N bonds which permit facile chemical decomposition to monomeric units (polyol and isocyanate) for use in the synthesis of new PU materials. Reaction of PU materials with organic reagents such as glycols, water, or amines has shown promise in recovering polyol products; however, each has drawbacks which have thus far prevented their widespread use. Acidolysis, the reaction of PU with organic dicarboxylic acids (DCAs), offers polyol recovery under mild temperatures (< 200 °C) and atmospheric pressure, but its kinetics, mechanism, and scalability are not well understood. Here we develop quantitative relationships between DCA structure and PUF acidolysis function for ∼10 different DCA reagents. PUF acidolysis kinetics were quantified with ∼1 s time resolution using the rate of carbon dioxide (CO2) gas generation, which is shown to occur concomitantly with polyol release. Our findings demonstrate that DCA carboxyl group proximity and phase of transport are descriptors of PUF acidolysis rates, rather than expected descriptors like pKa. DCAs with closer proximity acid groups exhibited faster PUF acidolysis rate constants. Furthermore, a shrinking core mechanism effectively describes the kinetic functional form of the kinetics of PUF acidolysis by DCAs. The viability of this reaction in a real-world application is validated with kinetics of post-consumer polyurethane mattress waste. Our findings offer design rules that can guide the development of PU acidolysis processes and progress towards circularity of PU materials.
