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. Thisis accomplished byusing an asymmetric ,-diene containing a terminal double bond and an acrylate, whichis polymerized in the presence of multifunctional acrylates as selective and irreversible chain transfer agents using Hoveyda-Grubbs second generation catalyst. High cross-metathesis selectivitiesare achieved at low temperatures enabling good control over molecular weights. Furthermore, additional polyethyleneglycol (PEG) blocksare attached to these polymersvia 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.