Photocontrolled degradation of stimuli-responsive poly(ethyl glyoxylate): Differentiating features and traceless ambient depolymerization
The depolymerization of coatings prepared from a 6-nitroveratryl carbonate end-capped poly(ethyl glyoxylate) (PEtG) self-immolative polymer was studied. This polymer undergoes end-to-end depolymerization following cleavage of the end-cap by UV light. Several important fundamental differences between this class of polymers and conventional degradable polymers were revealed. For example, polymer backbone cleavage and depolymerization exhibited different dependencies on pH, emphasizing the decoupling of these processes. Probing of the coating erosion mechanism illustrated an interesting combination of features from surface erosion and bulk degradation mechanisms that arise from the end-to-end depolymerization mechanism and further differentiate these polymers from convention degradable polymers. It was also demonstrated that, unlike backbone cleavage, PEtG depolymerization did not exhibit a dependence on water and that PEtG could depolymerize back to the volatile monomer ethyl glyoxylate at ambient temperature and pressure. This unusual feature was utilized to perform facile polymer reprogramming/recycling via an irradiation-trapping-repolymerization sequence as well as polymer patterning by a simple irradiation-evaporation sequence.