Photocontrolled Degradation of Stimuli-Responsive Poly(ethyl glyoxylate): Differentiating Features and Traceless Ambient Depolymerization

Abstract

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.

Poly(ethyl glyoxylate)-Poly(ethylene oxide) Nanoparticles: Stimuli-Responsive Drug Release via End-to-End Polyglyoxylate Depolymerization

“…[19][20][21] This provides the potential for signal amplification at low stimulus concentrations. End-caps responsive to stimuli such as light [22][23][24] , H 2 O 2 25,26 , thiols 24,27 , and mildly acidic conditions 28 have been reported and have been used in applications such as sensors 25,29,30 and responsive coatings or plastics [31][32][33] . The incorporation of a second polymer block has provided amphiphilic copolymers that self-assembled to form nanoparticles such as micelles and vesicles.…”

Reflections on the Evolution of Smart Polymers

“…[128][129] SIPs can also be depolymerized back to monomers for reprocessing using preprogrammed triggers. [130][131] Ultimately, smart polymer approaches have potential to enable polymers to retain stability as desired during their use, but degrade on command. In addition, while some of the first synthetic polymers were developed to replace natural biopolymers, ironically there is now great interest in replacing synthetic polymers with biobased polymers.…”

Sunlight photodepolymerization of transient polymers

“…Photolabile protecting end groups have been used to initiate photo‐depolymerization of aliphatic polyglyoxylates . However, the depolymerization occurs over several days and the wavelength of activation is difficult to control.…”