Synthesis and properties of couplable ABCDE star copolymers by orthogonal CuAAC and Diels-Alder click reactions

The exploration on robust methods to construct star copolymers has attracted much attention. Owing to the great challenge in synthesis, the examples of miktoarm stars with chemical compositions up to five or more are very scarce. This study aims at developing a modular and orthogonal approach to synthesize multicomponent stars via a one-pot strategy using distinct building blocks. Tandem CuAAC and Diels-Alder reactions were utilized to generate an ABCDE star comprising poly(epsilon-caprolactone) (PCL, A), poly (tert-butyl acrylate) (PtBA, B), poly(L-lactide) (PLLA, C), poly(N-isopropylacrylamide) (PNIPAM, D) and poly (5-methyl-5-allyloxycarbonyl-1,3-dioxane-2-one) (PMAC, E) arms, and a subsequent hydrolysis afforded an AB'CDE (B' = poly(acrylic acid)) star with clickable and dual-sensitive segments. The star copolymers were liable to self-assemble into intriguing morphologies involving vesicles, spherical micelles and large compound micelles which could be tuned by adopting thermal and pH stimuli. The modular synthesis using orthogonal chemistry allows us to prepare ABCDE-type stars with well-controlled molecular weight, tunable composition, and versatile functions. The success of this study further paves the way for facile synthesis of multifunctional star quintopolymers and their derivatives with multipurpose applications.