Self-Assembly of Coil-Bottlebrush Block Polymers

Diblock copolymers self-assemble into a variety of periodic nanostructures, such as spherical micelles, cylinders, lamellae, and 3D networks. Network structures consist of reoccurring interpenetrating nanodomains. The bicontinuous nature of the network domains provides the opportunity to design materials with several combined properties. However, access to applications has been limited because self-assembly of linear diblocks into network phases tends to occur only over narrow compositions. Moreover, the slow self-assembly kinetics at high molecular weight places upper limits the accessible pore size of the network structures. Polymers with a bottlebrush architecture are expected to provide access to larger domains due to an extended backbone chain conformation and faster ordering kinetics. We have synthesized diblock copolymers with a coil-brush architecture through ring-opening metathesis polymerization. By combining the coil and the brush architectures in one diblock, we change the overall shape of the molecule, and affect the polymer packing into network phases. By a combination of molecular and structural characterization methods, we show that the shape of the polymer and the identity of the coil block give significant control over the compositions, compositional window size, and molecular weights available for network formation.