Alkali metal-biphenyl complexes

ABA triblock copolymers cannot be produced by monofiinctional initiation when the A anion is not sufficiently basic to initiate polymerization of B monomers. In such cases the bifunctional initiators like alkali metal complexes of polycyclic aromatic compounds (e.g., naphthalene and biphenyl) can be used to produce ABA triblock copolymers. In these cases polymerization would be started with monomer B to produce a polymeric dianion which would initiate polymerization of the A monomer that is added later. The process is illustrated below for the commercially important styrene-butadiene-styrene (SBS) triblock copolymer ... 

The technique of forming n complexes in a metal atom generator is useful for arene-metal complexes , and is outlined in 5.8.2.9.3. Related in mechanism is a solution-phase technique for reducing metal halides to lower valent states with alkali metals in the presence of arenes. By this method bis( j -biphenyl)Cr(I) cation is obtained in 60% yield ... 

Bifunctional Initiators Bifunctional initiators like alkali metal complexes of polycyclic aromatic compounds (e.g., naphthalene and biphenyl) can be used to produce ABA triblock copolymers. In... 

---