Star block copolymers and hexafullerene stars via derivatization of star-shaped polystyrenes

The end-functionalization of hexaarm star-shaped polystyrene (PS), prepared via "living" cationic polymerization, by organosilicon compounds was inves tigated. The presence of a sec-chlorine atom at each branch end was first c onfirmed by H-1 NMR. After activation of these chain ends by TiCl4, both al lylic and azido groups were introduced through the use of their trimethylsi lyl derivatives (allyltrimethylsilane and trimethylsilyl azide, respectivel y), particularly taking advantage of the high affinity of silicon compounds toward electrophilic reagents. These end-standing allyl and azide function s on the hexaarm PS stars were then transformed into hydroxyl and amino gro ups with use of classical organic chemistry reactions. PS stars carrying si x fullerenes on their periphery were also generated from hexaazido star sam ples. The presence of these six C-60 entities was confirmed by miscellaneou s characterization methods, including H-1 NMR, size-exclusion chromatograph y, thermal gravimetry, and cyclic voltammetry. Besides the synthesis of the se omega-functionalized stars, PS6-b-PEO6 star block copolymers were also p repared with use of the hexahydroxy samples as macroinitiators of ethylene oxide polymerization.