Molecular Dynamics Simulations for Triblock Oligomers with 1-Nm Self-Assembled Domains

Self-assembly of block polymers that contain chemically distinct segments can form a wide variety of nanostructures with sub-10 nm feature sizes, for applications ranging from templates for nanopatterning to ion transport membranes for batteries. However, reducing the self-assembled feature size below 5 nm can be challenging. Miniaturization of the feature sizes can be achieved by block oligomers or block molecules with rigid-flexible motifs and short-range intermolecular interactions. In this study, we used molecular dynamics simulation to investigate the solvent-free phase behavior of a series of triblock oligomers composed of polyalcohol and hydrocarbon blocks. Depending on the molecular architectures, they exhibit thermotropic liquid crystallinity and self-assemble into ordered nanostructures include lamellae, perforated lamellae, and hexagonally-perforated lamellae with periodic domain pitches as small as 1.2 nm. Above the order-disorder transition temperature, the long-range order of these structures is lost while the local segregation is still preserved. Cluster analysis of the hydrogen-bonded and the nonpolar networks reveals the bicontinuous nature of the observed disordered structures, with even smaller characteristic dimensions as compared to their ordered states. The detailed molecular-level insights provided by simulation facilitates the understanding of structure-property relationships for the formation of mesophases on the 1-nm length scale.