Polyesteracetals via TBD Catalyzed Ring-Opening Polymerization

Polyacetals represent a novel category of degradable polymers, exhibiting remarkable potential for utilization in biomedical and pharmaceutical applications due to their controllable degradation behavior under physiological conditions. The organocatalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was used for the ring-opening polymerization (ROP) of 2-methyl-1,3-dioxane-4-one. Whereas standard reaction conditions, suitable for lactide polymerization resulted in a polyester due to loss of acetaldehyde, the amount of esteracetal repeating units could be tailored by the polymerization conditions. Performing the ROP at -35°C at a monomer concentration of 15 mol L^-1 maximized the incorporation of labile acetal groups to 50 mol%. The versatility of this polymerization system was demonstrated through the successful initiation with a wide range of alcohols, including 1-pyrenemethanol for end-group analysis via size exclusion chromatography with UV detection and matrix-assisted laser desorption-ionization mass spectrometry, as well as various macroinitiators such as mono- and bifunctional poly(ethylene glycol)s, poly(2-ethyl-2-oxazoline), poly(2-n-nonyl-2-oxazoline), and poly(2-iso-propyl-2-oxazoline), thereby facilitating the synthesis of well-defined block copolymers.