Formation of biobased-polycarbonates via amorphous solid-state polymerization of isosorbide/isomannide with fluorinated carbonate

Abstract Polycarbonates (PC) derived from bio-derived diol monomers, isosorbide (ISB) and isomannide (IMN), are attractive alternatives to bisphenol A (BPA) PCs owing to their fused-bicyclic main chain structures. However, conventional solid-state polymerization (SSP) of amorphous polycarbonates requires crystallization of the monomers or oligomeric prepolymers. Previously, we disclosed the amorphous SSP of BPA with bis(1,1,1,3,3,3-hexafluoro-2-propyl) carbonate (BHFC), which efficiently synthesizes high-molecular-weight PCs. Here, we present the first synthesis of biobased PCs via amorphous SSP of a prepolymer prepared from ISB/IMN with BHFC. During the SSP, the reaction temperature was increased stepwise to 170°C, affording moderate- to high-molecular-weight poly(ISB carbonate)s and poly(ISB/IMN carbonate)s. Increasing the feed ratio decreased the molecular weight of the poly(ISB/IMN carbonate) copolymer. We also combined IMN with the bis(hexafluoroisopropyl carbonate) of IMN (IMNBFC) to obtain poly(IMN carbonate). Furthermore, ISB combined with IMNBFC afforded a copolymer consisting of alternating ISB and IMN units. No crystalline structures were observed during any SSP process or the resulting PCs. The PCs achieved satisfactorily high thermal stabilities, high glass transition temperatures, and low discoloration because the SSP was performed at lower temperatures than conventional melt polymerization.