Thin Film Crystallization of Molecular Bottlebrushes

Thin film crystallization of molecular bottlebrushes bearing semicrystalline poly(ethylene oxide) (PEO) chains has been investigated. The unique bottlebrush architecture results in rich crystalline morphologies in ultrathin films, including flat-on single crystals and fiber-like structures, with the fiber-like crystals being the predominant phase. This observed morphology sharply contrasts with the behavior of linear PEO, where flat-on crystals dominate in ultrathin films, and relatively thicker films typically exhibit edge-on crystals. The growth of these fiber-like crystals was monitored using in situ atomic force microscopy (AFM) and optical microscopy, which revealed anisotropic growth rates. A detailed chain packing mechanism will be discussed. Our findings underscore the significant influence of both the solid substrate's confinement and the tethering chain effect associated with the mBB architecture on the pathways of polymer crystallization.