Janus [3:5] Polystyrene–Polydimethylsiloxane Star Polymers with a Cubic Core

We describe the precision synthesis and self-assembly of a series of Janus star polymers with mixed [3:5] heteroarms of polystyrene (PS) and polydimethylsiloxane (PDMS) precisely arranged on a cubic scaffold of T8 polyhedral oligomeric silsesquioxane (POSS) in a spatially segregated fashion. The synthesis begins with a Janus POSS compound with three 2-hydroxylethyl groups on one face and five vinyl pendant groups on the rest vertexes. Facilitated by esterification and a “click” adaptor, two types of polymer arms are attached efficiently by sequential “click” reactions, which constitutes a general approach for modular synthesis of such Janus star polymers. The Janus feature is thoroughly characterized using NMR, FT-IR, SEC, and MALDI-TOF mass spectrometry, and the self-assembled structures are studied by small-angle X-ray scattering (SAXS) experiments. With increasing molecular weight of PS arm, the self-assembled phase transits from lamellae (LAM) to hexagonally packed cylinder (HEX) and further to invers...