Synthesis of star-branched polymers by means of anionic living polymerization coupled with functional group transformation

To synthesize well-defined regular and heteroarmed star-branched polymers, we have developed a new and versatile methodology based on anionic living polymerization coupled with functional group transformation. The synthetic procedure employed in our methodology involves the following three reaction stages: The first stage is to prepare the precursory polymers with a defined number of methoxymethylphenyl groups by reacting polystyryllithium with specially designed reagents. The methoxymethylphenyl groups thus introduced are quantitatively transformed into chloromethylphenyl groups in the second stage reaction. At the third stage, anionic living polymers are reacted to couple with the chlorinated precursory polymers to afford the desired star-branched polymers. in fact, well-controlled three-, four-, and six- armed star polystyrenes were successfully synthesized by using the above-mentioned procedure. More interestingly, well-defined hetero four-armed ABC(2) and five-armed AB(4) star polymers have been readily obtained simply by changing living polymers to be reacted. The resulting star-branched polymers were isolated by SEC fractionation. Their well-defined and controlled structures were demonstrated by SEC, H-1 NMR, light scattering, and viscosity measurements.