Current practices in the generation and disposal of synthetic polymers are largely unsustainable, causing severe worldwide polymer pollution and enormous materials value loss. To address these dire environmental and economic issues, several research fronts aim to develop sustainable polymers with closed-loop life cycles. Current practices in the generation and disposal of synthetic polymers are largely unsustainable, causing severe worldwide polymer pollution and enormous materials value loss. To address these dire environmental and economic issues, several research fronts aim to develop sustainable polymers with closed-loop life cycles.