Hydrophilicity-Mediated Three-Dimensional Confined Assembly of Chiral Block Copolymers

Confined assembly of chiral block copolymers (BCPs*) affords an effective approach to preparing controllable chiral nanostructures, yet the interplay among molecular hydrophilicity, assembled morphology, and chiroptical properties remains unclear. In this study, we reported hydrophilicity-mediated three-dimensional (3D) confined assembly of poly(2-vinylpyridine)-block-poly(L-lactide) (P2VP-b-PLLA) and P2VP-block-poly(D-lactide) (P2VP-b-PDLA) in evaporative emulsion droplets. The assembled morphology and the chiral transfer from a molecular configuration to a microphase-separated structure was found strongly dependent on the molecular mass (Mn) and the PLA volume fraction (fPLA) due to the amphiphilic feature of the P2VP block. Specifically, BCPs* with Mn ≥ 17.7 kDa and fPLA between 17 and 28% possessed relatively high hydrophobicity and formed solid spheres with an internal helical structure. In contrast, BCPs* with lower Mn and hence higher hydrophilicity gave rise to hollow assemblies lacking an evident chiral morphology. Moreover, the addition of protonic species such as H+ further enhanced the hydrophilicity of BCP* chains via the protonation of P2VP, thus modulating the assembly behavior of BCPs*. Similar manipulation could be achieved by the addition of Lewis acidic species, such as Cu2+ and Fe3+, which hydrolyzed and released H+. Chiroptical measurements revealed that the dissymmetry factor (g-factor) strongly depended on the assembled morphology: solid spheres with an internal helical structure exhibited significantly stronger circular dichroism responses than hollow morphologies. This work demonstrated hydrophilicity as a governing parameter for confined chiral assembly and chiroptical modulation and provided new insights into the development of functional chiral materials via hydrophilicity-mediated self-assembly.