Polyglyoxylamides with a pH-Mediated Solubility and Depolymerization Switch

• Published in: Macromolecules 2021-11, Vol.54 (22), p.10547-10556
• Main Authors: Sirianni, Quinton E. A, Liang, Xiaoli, Such, Georgina K, Gillies, Elizabeth R
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.1c01796

Self-immolative polymers (SIPs) are characterized by their ability to depolymerize in response to the cleavage of a single end-cap or backbone moiety, making them attractive for numerous applications including sensors, transient plastics, and delivery vehicles. For many applications, it would be desirable to have an SIP capable of depolymerizing selectively under mildly acidic aqueous conditions. However, the poor solubility of most SIPs in water, accompanied by the competing effects of end-cap cleavage and depolymerization mechanisms, has made this a challenge. Here, we describe the development of polyglyoxylamides (PGAms) with pendent amino groups to achieve solubility switching at mildly acidic pH, which allows access of water to the end-cap and consequently depolymerization. PGAms with varying amino groups were synthesized from trityl end-capped poly­(ethyl glyoxylate) (PEtG). While water-insoluble PEtG underwent no detectable depolymerization between pH 5 and 7.4 and water-soluble PGAms underwent rapid depolymerization regardless of pH in this range, a PGAm with N,N-diisopropylaminoethyl (DPAE) pendent groups underwent more rapid depolymerization at pH 5–6 compared to pH 7.4. PGAms were also incorporated into block copolymers with poly­(ethylene glycol) (PEG). Nanoassemblies formed from PEG-PGAm­(DPAE), swelled, disassembled, and depolymerized as the pH was lowered from 8 to 5. Copolymers lacking a solubility switch did not undergo pH-dependent disassembly or depolymerization. Overall, this work provides a new platform approach for the development of pH-sensitive SIP materials for a wide range of applications.