Acyclic diene metathesis polymerization and heck polymer-polymer conjugation for the synthesis of star-shaped block copolymers.

Three- and four-arm star shaped polymers, as well as diblock copolymers, are synthesized via acyclic diene metathesis (ADMET) polymerization. This is accomplished by using an asymmetric α,ω-diene containing a terminal double bond and an acrylate, which is polymerized in the presence of multifunctional acrylates as selective and irreversible chain transfer agents using Hoveyda-Grubbs second generation catalyst. High cross-metathesis selectivities are achieved at low temperatures enabling good control over molecular weights. Furthermore, additional polyethyleneglycol (PEG) blocks are attached to these polymers via Heck coupling of the acrylate end-groups of these polymers with aryl iodide functionalized PEG, obtaining three- and four-arm star shaped di- and triblock copolymers with molecular weights up to 31 kDa.