Poly(Glyceric Acid Carbonate) Is A Degradable Analog Of Poly(Acrylic Acid)

Poly(acrylic acid)s make up a versatile class of polymers that are produced at large scales and used in many applications. But the polymers have some drawbacks. Their all-carbon backbone means that they don’t degrade easily, and their water solubility makes them difficult to recover. Mark W. Grinstaff and coworkers at Boston University have now made analogs with degradable carbonate linkages built into every repeating unit that get around these problems. The researchers synthesized poly(glyceric acid carbonate)s via the ring-opening copolymerization of a benzyl glycidate with CO₂ in the presence of bifunctional cobalt salen catalysts to yield benzyl-protected polymers (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b07911). Removal of the benzyl protecting groups via palladium-catalyzed hydrogenolysis yields the desired polymer. In deionized water, the poly(glyceric acid carbonate) degrades into glyceric acid and CO₂ with a half-life of about 12 days, whereas poly(acrylic acid) doesn’t degrade at all. Similarly, a hydrogel made by cross-linking poly(glyceric acid carbonate) with poly(ethylene glycol) and aziridine degraded more rapidly than the corresponding poly(acrylic acid) hydrogel. The new polymers could be useful for a wide range of chemical, biomedical, and pharmaceutical applications, the researchers propose.