Efficient Synthesis of Asymmetric Miktoarm Star Polymers

• Published in: Macromolecules Vol. 53; no. 2; pp. 702 - 710
• Main Authors: Levi, Adam E, Fu, Liangbing, Lequieu, Joshua, Horne, Jacob D, Blankenship, Jacob, Mukherjee, Sanjoy, Zhang, Tianqi, Fredrickson, Glenn H, Gutekunst, Will R, Bates, Christopher M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28.01.2020
• Subjects: asymmetric star; grafting-through polymerization; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; macromonomer; miktoarm star; polymer architecture; ring-opening metathesis polymerization; ROMP; miktoarm star; asymmetric star; polymer architecture; ROMP; macromonomer; ring-opening metathesis polymerization; grafting-through polymerization
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.9b02380

Asymmetric miktoarm star polymers produce unique material properties, yet existing synthetic strategies are beleaguered by complicated reaction schemes restricted in both the monomer scope and yield. Here, we introduce a new synthetic approach coined “μSTAR”, miktoarm synthesis by termination after ring-opening metathesis polymerization, that circumvents these traditional synthetic limitations by constructing the block–block junction in a scalable one-pot process involving (1) grafting-through polymerization of a macromonomer followed by (2) in situ enyne-mediated termination to install a single mikto-arm with exceptional efficiency. This modular μSTAR platform cleanly generates AB n and A­(BA′) n miktoarm star polymers with unprecedented versatility in the selection of A and B chemistries as demonstrated using many common polymer building blocks. The average number of B or BA′ arms (n) is easily controlled by the equivalents of Grubbs catalyst. While these materials are characterized by dispersity in n that arises from the statistics of polymerization, they self-assemble into mesophases that are identical to those predicted for precise miktoarm stars. In summary, the μSTAR technique provides a significant boost in design flexibility and synthetic simplicity while retaining the salient phase behavior of precise miktoarm star materials.