Unique Base-Initiated Depolymerization of Limonene-Derived Polycarbonates

Abstract

The depolymerization of poly(limonene carbonate) (PLC) initiated by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was investigated. The strong organic base TBD was capable of deprotonating the OH-terminated PLC, leading to fast degradation via backbiting reactions at high temperature. An interesting feature of the base-initiated breakdown of PLC lies in the quantitative depolymerization into the corresponding initial limonene oxide monomer. This result implies the complete back-to-monomer recyclability of the fully biobased PLC, which accordingly can be considered as a really sustainable material. Additionally, the stability of PLC when exposed to TBD was enhanced by an end-capping reaction, which further supported the proposed degradation pathway.

Polymers of Limonene Oxide and Carbon Dioxide: Polycarbonates of the Solar Economy

“…These biobased polymers hold great potential for practical utilization, given both their excellent sustainability profile (with complete back-to-monomer recyclability) 19 and a vast scope of potential applications, which include protecting coatings, 20 breathing-glass windows, 10 and the addition of permanent antibacterial activity and hydrophilization. 11…”

Organocatalysis for depolymerisation

“…With the same objective of building a sustainable polymer cycle, another recent example involved the depolymerisation of an innovative limonene-based polycarbonate into a limonenederivative epoxide, using TBD as catalyst. 84 In this study, Li et al demonstrated that the scission of the polymer chain was initiated by the deprotonation of the hydroxyl chain ends of the polymer before a chain transfer process released one molecule of monomer (Scheme 12b). This mechanism selec-Scheme 10 Depolymerisation of PHB into TBL.…”

From terpenes to sustainable and functional polymers

“…8) through a back-biting mechanism. 117 Such controlled depolymerisation can set the basis for efficient recycling of PLC and developing sustainable material solutions based on a renewable building block. 118…”