Accessing block copolymers with independently modulated tacticities using sequential cationic–anionic polymerization of vinyl ethers and thiiranes

Abstract

Tacticity can have profound effects on the physical properties of polymers, such as self-assembly of block copolymers (BCPs). Despite its promise, previous reports on changing tacticity of BCPs have primarily focused on changing a single block or comparing fully isotactic to fully atactic copolymers. Herein, we report a platform to easily access fully atactic, fully isotactic, and mixed tacticity poly(vinyl ether)-block-poly(thiirane) BCPs. Isotacticity was independently accessed via stereoselective polymerization of vinyl ethers and by using enantiopure thiirane monomers, respectively. Thermal analyses of these materials were performed and semi-crystallinity was observed in aryl-containing isotactic blocks. For BCPs with alkyl side chains or atactic aryl side chains, fractionation on the basis of composition was performed to accelerate self-assembly studies. These fractionated BCPs were characterized via small-angle X-ray scattering (SAXS), where we observed hexagonally-packed cylinder or lamellar morphologies for some fractions. The development of this framework of selective tacticity modulation opens up facile access to diverse BCPs with varying thermal, solution-state, and bulk properties.