Star Block Copolymer Nanoassemblies: Block Sequence is All-Important

Star and linear block copolymers of [poly­(4-vinylpyridine)-block-polystyrene]_n [(P4VP-b-PS)_n] and [polystyrene-block-poly­(4-vinylpyridine)]_n [(PS-b-P4VP)_n] (n = 1–4) with similar chemical composition but different block sequence were synthesized by RAFT polymerization. Star (P4VP-b-PS)_n is composed of a jointed P4VP core and several outer PS arms, and (PS-b-P4VP)_n has just the opposite block sequence and different conformation. The effect of block sequence on the block copolymer nanoassemblies is explored. It is discovered that star (P4VP-b-PS)_n tends to form complicated nanoassemblies in the block selective solvent for P4VP due to the PS arms bridging, and star (PS-b-P4VP)_n acts somewhat like linear amphiphilic block copolymers. Our study demonstrates the crucial role of block sequence in star block copolymer nanoassemblies.