Self-immolative polymers (SIPs) are a class of stimuli-responsive materials that undergo controlled end-to-end depolymerization in response to stimuli. Their unique degradation and amplification properties have made them of interest for a diverse array of applications including sensors, vehicles for controlled release, and transient objects. Thus far, a limited number of SIP backbones exist, each with its own advantages and limitations. We report here the preparation and study of polyglyoxylamides (PGAms) as a new class of SIPs. PGAms were synthesized by simple postpolymerization modifications of poly(ethyl glyoxylate) (PEtG). While retaining the important stimuli-responsive depolymerization properties of polyglyoxylates, PGAms exhibited much different thermal properties, and some were even water-soluble. Furthermore, a depolymerizable PGAm analogue of poly(ethylene glycol) was prepared, demonstrating the capability to synthesize more complex PGAm graft copolymers. Overall, PGAms are a new class of SIPs with unique combinations of physical, thermal, and degradative properties that provide avenues for novel applications.

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A series of polyglyoxylamides (PGAms) have been synthesized and investigated for performance as kinetic hydrate inhibitors (KHIs) in slow constant cooling high-pressure rocking cell experiments using a structure II-forming synthetic natural gas mixture at 76 bar initial pressure. We found that the KHI performance improved as the size of the alkyl pendant group was increased. The best performing PGAm, poly(pyrrolidinyl glyoxylamide) (PPyGAm-I), gave an onset temperature of 8.2 °C at 2500 ppm. The KHI performance was improved by increasing the polymer concentration or by adding the high-flashpoint solvent n-butyl glycol ether (nBGE) as a synergist. For example, using 7500 ppm of PPyGAm-I, the onset temperature was lowered to 3.8 °C (giving a subcooling of 15.7 °C, compensating for the drop in pressure at T o ). A mixture of 2500 ppm PPyGAm-I and 7500 ppm nBGE gave an onset temperature of 5.1 °C. Combined with a high cloud point (T Cl = 79 °C), this makes PPyGAm-I a strong candidate for potential industrial use. The seawater biodegradability of the PGAms in this study was found to be low, 4−17%, according to the 28-day marine OECD306 test protocol. However, this can be improved by changing the polymer's end groups, grafting, or by utilizing the polymer's susceptibility to acid hydrolysis.

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.

Nucleic acids have immense potential for the treatment and prevention of a wide range of diseases, but delivery vehicles are needed to assist with their entry into cells. Polycations can...