Janus Triad: Three Types of Nonspherical, Nanoscale Janus Particles from One Single Triblock Terpolymer

We report the synthesis of three different Janus topologies from one single specific triblock terpolymer, poly (tert-butoxystyrene)-block-polybutadiene-block-poly(tert-butyl methacrylate) (tSBT). By controlling the phase transitions via pretreatment and cross-linking conditions of the lamella-cylinder equilibrium bulk morphology of the polymer, we were able to obtain Janus cylinders, sheets, and previously unknown Janus ribbons. Here, a delicate balance of experimental parameters allows to manipulate the microphase morphologies as needed. The attained control even realizes the trapping of a complex intermediate phase, where every second intercylinder distance in the lamella-cylinder morphology is connected by a thin lamella. Furthermore, we also show that casting from a selective solvent can be used to access the lamella-sphere morphology and fabricate spherical Janus particles. What is more, poly(tert-butoxystyrene) can be hydrolyzed to polyhydroxystyrene, which is water-soluble at high pH and thus pH-responsive. It also represents a reaction site for further functionalizations and is thus an attractive alternative to the commonly used polystyrene. We furthermore present cryo-TEM images of water-soluble Janus cylinders that include one of the best quasi in-situ real-space proofs for the Janus character of nanosized, anisometric polymer-based particles.