AB 2 Functional Polyesters via Ring Opening Polymerization: Synthesis and Characterization

Aliphatic AB 2 functional polyesters were conveniently prepared by the ring opening polymerization of ε ‐caprolactone and L ‐lactide in the presence of the AB 2 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 AB 2 ‐functional PLLA and PCL polymers were comparable to linear polymers with a $\overline {DP}$ equal to the $\overline {DP}$ per arm in the polymer.