Description of solution

The preparation of limonene-based polycarbonate is based on several synthetic steps. In a first step, poly(limonene)carbonate (PLC) is formed from limonene oxide and carbon dioxide. The resulting polymer contains a repeating unit having a pendent double bond which is epoxidized in a second step and further converted in a cyclic carbonate in a third step, thus yielding the poly(limonene)dicarbonate. The resulting PLDC products exhibits an unusually high glass transition temperature, which makes it suitable for certain applications, such as coating applications. The method performs the synthesis of the PLDC from limonene by sequential epoxidation/carboxylation of the limonene. One advantage is that both isomers of limonene oxide are reactive in the ring-opening polymerization leading to polylimonenecarbonate (PLC), such that there is no need to upgrade or purify commercial limonene oxide to a single diasteroisomer. Noteworthy, the pendent double bond in PLC can further be functionalized through chemical modification in order to introduce functionality to the prepared polymer. The resulting ingredients may be used in the formulation of coating applications.

In a similar manner, the preparation of polyesters from limonene can be performed by ring-opening copolymerization (ROCOP) in presence of various polyaromatic anhydrides. The process uses a specific catalyst allowing the formation of a polymer with a narrow index of polydispersity than the catalysts described in the state of the art. The developed process affords high conversion of anhydride, leading to high molecular weight polymers with reasonable indexes of polydispersity. Last but not least, the prepared polyesters benefit from high glass transition temperatures.  The copolymerization reactions proceed with excellent selectivity toward fully alternating polyesters (≥98% ester bonds)

Advantages and unique selling points

• Biobased monomers: Limonene can be obtained from citrus peel. Nowadays, most limonene is produced from citrus rind, a major by-product generated during fruit processing in citrus juice industries. Global limonene production is increasing at a rapid rate and is predicted to exceed 65 kT by 2023, with a considerable untapped potential.
• Readily available reagents: CO₂ is used as a reagent: carbon dioxide is cheap, readily available in large amounts and is currently an environmental concern for its greenhouse effect. Limonene oxide is readily available from limonene obtained by extraction from citrus peel, a waste for agrofood industry.
• Functionality on-demand: PLC has a pendant double bond per repeating unit. This fact allows to change its properties using click chemistry or epoxidation chemistry. Various functionalities can thus be introduced, thus leading to the preparation of active materials useful in the formulation of performance materials.
• Recyclability: Recyclability for its monomers has been described. Chemical degradation of polymeric PLC to monomer is possible.
• Excellent selectivity: The copolymerization reactions proceed with excellent selectivity toward fully alternating polyesters (≥98% ester bonds).

Collaborators

Fundació Institut Català d’Investigació Química (ICIQ) and Institució Catalana de Recerca i Estudis Avançats (ICREA).