Sequence-controlled polymers ring-opening

Some examples of sequence-controlled polymers prepared by ring opening polymerization of cyclic esters have been reported. For instance, Thomas, Coates, and coworkers reported a very original method for the synthesis of alternating aliphatic polyesters.These authors used a stereoselective yttrium-based organometallic catalyst to control comonomer sequences. It had been previously shown that the polymerization of a racemic mixture of p-butyrolactone in the presence of this catalyst led to the formation of... 

It has been shown recently (10) that such block structures could be tailored precisely by the general method summarized hereabove. It is indeed possible to convert the hydroxyl end-group of a vinyl polymer PA (f.i. polystyrene, or polybutadiene obtained by anionic polymerization terminated with ethylene oxide),into an aluminum alcoholate structure since it is well known that CL polymerizes in a perfectly "living" manner by ring-opening insertion into the Al-0 bond (11), the following reaction sequence provides a direct access to the desired copolymers, with an accurate control of the molecular parameters of the two blocks ... 

---