High-χ alternating copolymers for accessing sub-5 nm domains via simulations.

The ever-growing semiconductor industry has encouraged the feature dimensions of nanolithography to reach the sub-10 nm length scale. It is highly necessary to find nanolithographic materials with high performance but ultra-small domains. We have designed a series of high-χ alternating copolymers (ACPs), in which the polar and apolar repeating units are four hydroxyl groups and alkyl chains, respectively. Careful coarse-grained molecular dynamics (CG-MD) simulations demonstrate that these ACPs can form a variety of mesophases, including lamellae, perforated lamellae, and hexagonally packed cylinders. All the domain periods of these mesophases are smaller than 5 nm, and the smallest domain is close to 1 nm. Most importantly, both the phase morphologies and domain periods are independent of the molecular weight (MW) and molecular weight distribution (MWD) when the degree of polymerization (N) exceeds the threshold value. Thus, using high-χ ACPs, ultranarrow domains can be realized with high MW for sufficient material performance, while the MWD-independence can ensure the uniformity of the domain sizes. We believe that these "high χ-high N" alternating copolymers are promising alternatives as new nanolithographic materials.