Direct evidence of star structure from nuclear magnetic resonance spectroscopy

Until now the characterization of a star‐like structure has been based on an indirect method, i.e. the comparison of the molecular weight of the star polymer and its linear precursor. By preparing well‐defined and narrow‐molecular‐weight‐distribution polybutadiene and polyisoprene stars with up to four arms — using anionic polymerization techniques and the appropriate chlorosilane — and by characterising them by means of ¹H and ¹³C NMR spectroscopy, the key point of the star, which is the core next to the silicon atom, was observed.