Polylactide (PLA) is a biodegradable and renewable polymer, but it is not mechanically tough. Cellulose is an extremely abundant renewable feedstock, but it is difficult to process and also not mechanically tough. Thus, applications of these polymers are limited to those in which little stress is involved. PLA can be toughened by making it into a thermoplastic elastomer. They typical strategy involved adding PLA blocks both chain ends of a soft polymer block (e.g., polybuadiene) to form an ABA triblock copolymer. The core polybuadiene block is, however, not degradable. We describe here a method to incorporate a photodegradable component into the polybutadiene core block. This material is both tough and fully degradable, with light-triggered degradation of the core block and biodegradation of the PLA blocks. We apply a similar strategy to make cellulose copolymers, including thermoplastic elastomers, that are photo- and bio-degradable.