Facile Synthesis and Visualization of Janus Double-Brush Copolymers.

Well-defined double-brush copolymers with each graft site carrying a polystyrene (PSt) graft and a polylactide (PLA) graft were synthesized by simultaneous reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerization (ROP) processes, followed by ring-opening metathesis polymerization (ROMP) "grafting through" of the resulting diblock macromonomer (MM). Their Janus-type morphologies were detected by transmission electron microscopy (TEM) imaging after thermal annealing to facilitate the intramolecular self-assembly of PSt and PLA grafts. This finding provides critical evidence to verify double-brush copolymers as Janus nanomaterials.