Crystallization-driven solution self-assembly of block copolymers with a photocleavable junction.

Light-responsive block copolymers have been prepared with a crystallizable core-forming poly(ferrocenyldimethylsilane) (PFS) block, a corona-forming segment of poly(2-vinylpyridine) (P2VP), and a photocleavable o-nitrobenzyl (ONB) junction. These PFS-ONB-P2VP materials form monodisperse cylindrical micelles by living crystallization-driven self-assembly in a selective solvent for P2VP. The P2VP coronas were readily removed by photocleavage at the ONB linker, leading to PFS cylinders with a residual percentage of corona chains dependent on the photoirradiation time. Addition of PFS block copolymer unimers to a solution of the cylinders with ca. 10% residual coronal chains led to the formation of branched rather than linear micelles. The synthetic utility of the PFS-ONB-P2VP materials was further demonstrated by the preparation of nearly monodisperse P2VP nanotubes of tunable length using a strategy that also involved corona cross-linking.