Polymers with acid-labile linkages along the backbone are of great interest because of their ability to degrade rapidly into small molecules under acidic conditions, even at the early stage of the degradation. This presentation will focus on the development of advanced synthetic methodologies to afford well-defined polyphosphoramidates (PPAs) containing acid-labile backbone linkages (phosphoramidate bonds). Highly water-soluble PPAs with acid-labile backbone linkages were prepared readily under via organobase-catalyzed ring-opening polymerization (ROP) of a five-membered-ring monomer. The ROP kinetics were explored, demonstrating that these polymerizations proceeded in a controlled manner under basic conditions via the selective cleavage of P−O bonds during the ROP. Degradation studies indicated that these PPAs underwent rapid backbone degradation under acidic conditions through the cleavage of P−N bonds, yielding oligomers within several days at pH 5 (17.5% P−N bond cleavage after 3 d, DPn = 90). PPAs exhibited significantly faster degradation under acidic conditions, compared to months being required for their polyphosphoester analogs, which share the same structures except for the P-N linkages. α-Amino acids, based on their wide bioavailability and inherent biocompatibility are attractive starting materials for the development of novel synthetic biodegradable polymers. In addition, the introduction of α-amino acids may endow the polymer with additional advantages, such as desirable biological properties and enhanced thermal properties. The synthesis towards α-amino acid-based PPAs (APPA) via ROP was carefully evaluated. The hydrolytic degradation of the resulting highly water-soluble APPAs was studied, which revealed a faster degradation rate compared to its analog PPAs. Furthermore, the introduction of methyl carboxylate groups endowed the APPAs with intumescence, which makes it a potential candidate for advanced coatings applications.

Construction of polyphosphoramidates with acid-triggered backbone degradation

2019 Fall National Meeting

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