New Polymers from Sustainable Feedstocks
The renewed focus on the environmental footprint of polymer science is something that is very much welcomed – but also needs to be put in context of a persistent effort in pushing the boundaries of sustainable polymer science. The key is to understand the hierarchy of materials and optimal solutions. Especially where plastic waste is invisible, multi-lamellar or hard to capture, biodegradables offer a powerful improvement to sustainability. Our group has been focusing on exploring new methodologies to synthesize biodegradable aliphatic polyesters from sustainable feedstocks, especially for invisible waste applications. This project sits at the interface between extensive monomer and catalyst design and in-depth mechanistic investigations. Driven by industrial demand, we develop economical routes towards degradable polymers, with a particular focus on clean biodegradation / compostability and chemical depolymerisation. In particular, DOX monomers (1,3-dioxolan-4-ones) provide facile access to a range of novel monomers from renewable α-hydroxy acids and can be polymerized to give structurally divergent aliphatic polyesters with complete retention of stereochemistry. With a comprehensive understanding on the polymerization mechanism of DOX monomers, we have built a systematic approach to synthesizing biodegradable mimics of commercial non-degradable polystyrene from renewable mandelic acid. The resultant poly(mandelic acid)s have competitive thermal properties with polystyrene, highlighting the promising industrial applications of our research.
Cairns, S. A.; Schultheissa, A.; Shaver, M. P. “A broad scope of aliphatic polyesters prepared by elimination of small molecules from sustainable 1,3-dioxolan-4-ones” Polym. Chem. 2017, 8, 557
Xu, Y.; Perry, M. R.; Shaver, M. P. “Understanding the ring-opening polymerisation of dioxolanones” Polym. Chem. 2019
Olefin-Metathesis on Polymers
Olefin-metathesis offers a versatile methodology for introducing new functionality and generating new structures. We use olefin cross-metathesis in both pre- and post- polymerisation modification of biodegradable lactones to introduce an array of functional groups to tune the thermal properties of the polymers. We also use ring-closing metathesis as an efficient method to control the conformation of cyclopolymers. Further modification of the aforementioned rings can generate novel biometric polymeric materials.
Sinclair, F.; Chen, L.; Greenland, B. W.; Shaver, M. P. “Installing Multiple Functional Groups on Biodegradable Polyesters via Post-Polymerization Olefin Cross-Metathesis” Macromolecules 2016, 49, 6826