Monomer Recovery from and Recycling of Biobased Polyhydroxyurethanes

Past studies have demonstrated the recyclability of polyhydroxyurethane (PHU) networks exploiting available dynamic chemistries, reverse cyclic carbonate aminolysis and transcarbamoylation. These polymers are not infinitely recyclable as they undergo small levels of thermal degradation during each melt-state reprocessing step, eventually altering their desirable mechanical properties. To mitigate these drawbacks and provide further recycling options, monomer-like compounds were recovered from PHU via base-catalyzed solvolysis with methanol. These monomer-like compounds can be repolymerized into virgin PHU by transcarbamoylation or used separately as a bifunctional methyl carbamate and bifunctional vicinal diol for upcycling via synthesis of other step-growth polymers. Purification of solvolysis products can be achieved by boronate affinity chromatography, which selectively binds the vicinal diol product to the 4-vinylphenylboronic acid – styrene copolymer stationary phase.