POLY(2-VINYLPYRIDINE)-BASED STAR-SHAPED POLYMERS - SYNTHESIS OF HETEROARM STAR (A(N)B(N)) AND STAR-BLOCK (AB)(N) COPOLYMERS

Heteroarm star copolymers bearing poly(2-vinylpyridine) and polystyren e arms (A(n)B(n) type) were synthesized by a three-step anionic polyme rization method. Polystyrene arms are synthesized first, and they are used to initiate the polymerization of a small amount of divinylbenzen e, yielding polystyrene star molecules bearing a number of active site s within its cores. In a subsequent step poly(2-vinylpyridine) arms ar e growing from the cores. Poly(2-vinylpyridine)-block-poly(tert-butyl acrylate) star block copolymers [(AB)(n) type] were also prepared usin g the same synthetic route. In this case, short poly-styryllithium is used to build grafted poly(DVB) cores. These living plurifunctional in itiators can easily polymerize 2-vinylpyridine and subsequently tert-b utyl acrylate, yielding star molecules bearing diblock copolymers as a rms. The short polystyrene grafts of the core can be neglected and the star molecules are considered of the (AB)(n) type. These star polymer s have been characterized adequately and shown to exhibit rather well- defined structures. The advantages and the drawbacks of the method are discussed.