Ultrafast Self-Assembly of Bottlebrush Statistical Copolymers: Well-Ordered Nanostructures from One-Pot Polymerizations

Abstract

We report the synthesis of a bottlebrush statistical copolymer (BSCP) architecture and its role in directing molecular packing in the bulk state. Copolymers with a statistical distribution of two chemically distinct side chains on a common polymer backbone were prepared via one-pot ring-opening metathesis polymerization (ROMP) of norbornene-capped macromonomers with similar reactivities. Kinetic studies suggest a near-random compositional profile of polystyrene (PS) and poly(dimethyl siloxane) (PDMS) side chains along the backbone. The PS-stat-PDMS BSCPs with symmetric volume fractions rapidly assembled into lamellar microstructures when cast from solution without any further thermal or solvent annealing. The domain size is controlled by the side-chain length, ranging from below 10 nm to almost 20 nm. Furthermore, the bottlebrush statistical copolymer self-assembly yielded oriented lamellar morphologies over large areas after thermal annealing for 10 min at 200 °C without external guiding via surface or topographic patterning. Such statistical architectural control of the composition enables a simple preparation route for copolymers for potential use in the directed self-assembly of device architectures and other applications that require well-defined morphologies.