Key aspects to yield low dispersity of PEO-b-PCL diblock copolymers and their mesoscale self-assembly

Poly(ethylene oxide)-block-polycaprolactone (PEO-b-PCL) is one of the widely used biocompatible amphiphilic block copolymers which is able to self-assemble into a variety of 3D structures, including polymersomes. Controlled self-assembly into a 3D structure with a certain size and morphology might require uniform PEO-b-PCL (ĐM < 1.1), which has not been possible to synthesize so far. In this work, we optimized the well-known synthesis of PEO-b-PCL, catalyzed by SnOct2, leading to a low molecular-weight dispersity (< 1.1), and discussed the aging effects of SnOct2 on the overall kinetics of the synthesis. To understand the effect of the dispersity of PEO-b-PCL on its self-assembly, we compared self-assembled structures formed by uniform PEO-b-PCL (ĐM < 1.1) with the ones formed by non-uniform analogues (ĐM > 1.1). Furthermore, we demonstrated the benefits of uniform PEO-b-PCL when a high degree of end-group activation is required through ω-tosylation.