Aliphatic AB2 functional polyesters were conveniently prepared by the ring opening polymerization of ε-caprolactone and L-lactide in the presence of the AB2 functional initiator 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and Sn(Oct)2 as the catalyst. In L-lactide polymerization, both bis-MPA hydroxyl groups initiated the polymerization reaction, but for ε-caprolactone polymerization this depended on the monomer to initiator to catalyst ratio. Initiation at two hydroxyl groups occurred at high monomer to initiator ([M]/[I]) ratio and at high Sn(Oct)2 to monomer ratio. The melting temperatures of the AB2-functional PLLA and PCL polymers were comparable to linear polymers with a DP equal to the DP per arm in the polymer.
- Ring-opening polymerization