Novel amphiphilic ABC 3-miktoarm star azo-copolymer with polypeptide chain: Synthesis, self-assembly and photo-responsive behavior

Well-defined amphiphilic ABC 3-miktoarm star terpolymer containing hydrophilic methoxy poly(ethylene glycol) (MPEG), hydrophobic poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PAzoMA) and poly(γ-benzyl-L-glutamic acid) (PBLG) was synthesized by a combination of copper-mediated atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP). MPEG was modified to bear two different functional groups, which were further modified to the initiator of ATRP and ROP for the preparation of the amphiphilic ABC-type 3-miktoarm star terpolymers (MPEG) (PAzoMA) (PBLG). The spindle-like micelles were formed from the amphiphilic 3-miktoarm star terpolymer through a solution self-assembly due to the rigid ɑ-helical conformation of PBLG block and the π-π interaction between PBLG block with PAzoMA block in the star terpolymer. The investigation of the photo-isomerization behavior of (MPEG) (PAzoMA) (PBLG) in solution and in micellar solution showed that trans–cis isomerization in solution was quicker than that in micellar solution, and H- or J-aggregates of the azobenzene groups in the aggregates did not be observed. On the basis of the experimental results, the formation mechanisms of the spindle-like micelles were suggested and the obtained results may expand the self-assembly research field.