Simple Approach to Synthesize Carbohydrate-based Janus-Type Bottlebrush Copolymers and Their Self-Assemblies in Sub-5 nm Features in Thin Films

We demonstrate an original and simple route to synthesize oligosaccharides-based Janus-type bottlebrush block copolymers (BBCPs) with the combination of anionic polymerization, ring-opening metathesis polymerization, and click chemistry techniques following grafting-through and grafting-to approach. These Janus-type BBCPs having different molecular weights of side chains and backbone lengths undergo phase-segregation under conventional solvent vapor annealing (SVA) for 14–60 h or high temperature solvent vapor annealing (HTSVA) using μ-wave energy for 1 min, into long-range order sub-5 nm (half-pitch) periodic nanodomains in their thin films. This simple strategy could be used for large-scale production of Janus-type BBCPs, and side chains on either side of BBCPs could be replaced by a variety of other polymer systems. By replacing the oligosaccharides branches by other polymer systems like polylactide, polycaprolactone, or poly(ethylene oxide), we could further simplify this approach and reduce the number of steps (2 or 3) to reach the final product, i.e., from synthesis of macromonomer to final Janus-type BBCPs. It is noteworthy that it is the first report on achieving sub-5 nm nanofeatures in thin films using Janus-type BBCPs.