Efficient Synthesis of Asymmetric Miktoarm Star Polymers.

ABSTRACT: Asymmetric miktoarm star polymers comprising an unequal number of chemically-distinct blocks connected at a common junction produce unique material properties, yet existing synthetic strategies are beleaguered by complicated reaction schemes that are restricted in both monomer scope and yield. Here, we introduce a new synthetic approach coined "?STAR" - 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 ?STAR 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: poly(siloxane), poly(acrylate), poly(methacrylate), poly(ether), poly(ester), and poly(styrene). The average number of B or BA' arms (n) is easily controlled by the molar equivalents of macromonomer relative to Grubbs catalyst in the initial ring-opening metathesis polymerization step. While these materials are characterized by dispersity in n that arises from polymerization statistics, they self-assemble into mesophases that are identical to those predicted for precise miktoarm stars as evidenced by small-angle X-ray scattering experiments and self-consistent field theory simulations. In summary, the ?STAR technique provides a significant boost in design flexibility and synthetic simplicity while retaining the salient phase behavior of precise miktoarm star materials.

SUBMITTER: Levi AE 

PROVIDER: S-EPMC7266137 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature