Characterization and ammonolysis behavior of poly(isosorbide carbonate)-based copolymers

The development of recyclable polymers has attracted considerable attention for realizing the development of a sustainable society. Polycarbonates (PCs) are engineering plastics with high thermal stability and transparency. We focused on poly(isosorbide carbonate) (PIC), a bio-based PC synthesized from isosorbide (ISB) derived from glucose. PIC is expected to function as an alternative to conventional PCs because of its outstanding transparency and thermal and physical properties. This study prepared PIC copolymers with several types of diol comonomers to clarify the effect of copolymerization on the decomposition reaction with ammonia, i.e., ammonolysis for converting PIC copolymers into monomers and urea. The thermal and physical properties of the resulting copolymers were also investigated. The thermal stability of the PIC copolymers remained stable after copolymerization, and the glass transition temperature was affected mainly by the flexibility of the structure of the introduced comonomer. A drastic change in mechanical properties was observed for the copolymer synthesized with 1,4-butanediol, which provides guidelines for toughening PIC with a small comonomer ratio. Finally, we investigated the decomposition behavior of the copolymers by treatment with aqueous ammonia. The PIC copolymers were decomposed into ISB, comonomers, and urea, and the ammonolysis rate was affected by the introduced structure. This study promotes the effective use of ISB as a biomass resource through ammonolysis, which is an effective chemical recycling process for polycarbonate. To functionalize a poly(isosorbide carbonate) (PIC)-based polymer and evaluate its recyclability, several types of diol comonomers were copolymerized with isosorbide. The thermal and mechanical properties and decomposition behavior of the PIC copolymers were investigated. The thermal stability of PIC was retained, and its glass transition temperature was systematically controlled by copolymerization. The decomposition of the PIC copolymers upon treatment with aqueous ammonia yielded monomers and urea, and the decomposition rate was governed by the structure of the comonomer.