Comparison of salicylate-based poly(anhydride-esters) formed via melt-condensation versus solution polymerization.

Salicylate-based poly(anhydride-esters) were synthesized via two different methods, melt-condensation and solution polymerization, and the resulting polymers were compared. Acetylsalicylic acid was used as a model compound to mimic the active polymer chain-ends during melt-condensation, and formed a low-molecular-weight (<1500) polymer when subjected to melt-condensation polymerization conditions. The polymers and model compounds were analyzed by NMR ((1)H and (13)C) and IR spectroscopies to elucidate the structures. Spectroscopic analysis revealed the formation of a thermodynamically stable salicylate ester via salicylate-anhydride rearrangement during melt-condensation polymerization, which did not occur during solution polymerization. The salicylate-based poly(anhydride-esters) undergo a thermodynamic rearrangement during melt-condensation polymerization that is not observed for solution polymerization.