Hydrophilic Janus Micelles from an ABC Triblock Copolymer

Abstract

We describe the creation of an amphiphilic triblock copolymer that drives lateral phase separation within micelle coronas. The design combines a hydrophobic poly(lactide) (PLA) core ‑forming block with two distinct hydrophilic segments: poly(ethylene glycol) (PEG) and poly( N ‑vinylpyrrolidone) (PVP). In water, the copolymer assembles into spherical micelles, confirmed by cryogenic TEM and multi ‑angle light scattering. Selective end ‑labelling of PVP with an electron ‑dense iridium complex enabled unstained TEM imaging, revealing clear contrast asymmetry that locates PVP to a single hemisphere of the corona. Complementary 2D1 H-Nuclear Overhauser Effect Spectroscopy (1 H ‑NOESY) NMR confirmed this Janus ‑type segregation of PEG and PVP. These results demonstrate how molecular architecture can encode asymmetry into soft nanostructures, offering a versatile route to polymer ‑based Janus nanoparticles with dual surface functionality and broad technological potential.