Polyester-Based Diblock Copolymers

Considerable effort has been carried out by different groups in the preparation of amphiphihc block copolymers based on polyfethylene oxide) PEO and an ahphatic polyester. A common approach relies upon the use of preformed co- hydroxy PEO as macroinitiator precursors [51, 70]. Actually, the anionic ROP of ethylene oxide is readily initiated by alcohol molecules activated by potassium hydroxide in catalytic amounts. The equimolar reaction of the PEO hydroxy end group (s) with triethyl aluminum yields a macroinitiator that, according to the coordination-insertion mechanism previously discussed (see Sect. 2.1), is highly active in the eCL and LA polymerization. This strategy allows one to prepare di- or triblock copolymers depending on the functionality of the PEO macroinitiator (Scheme 13a,b). Diblock copolymers have also been successfully prepared by sequential addition of the cyclic ether (EO) and lactone monomers using tetraphenylporphynato aluminum alkoxides or chloride as the initiator [69]. 

PLA PLA-based block copolymers include diblock, triblock, and multiblock copolymers Jeon et al. (20(B), Chen et al. (2003), Pospiech et al. (2005) Blend with starch, other polyesters, and low molecular weight plasticizers such as glyc ol, sorbitol, and triethyl citrate Cargill (2007)... 

---