(691h) Understanding the Transition between Nanosheets, Nanotubes, and Nanohelices in Peptoid Assembly System

A long-standing challenge in bioinspired materials is to design and synthesize materials that mimic natural biomaterials' sophisticated structures and functions, such as helical protein assemblies that are important in biological systems. However, understanding the forces and dynamics that drive the process to control the material synthesis is challenging due to the various non-covalent forces involved, including ionic effects, hydrophobic effects, hydrogen bonds, and backbone chirality. Therefore, developing sequence-defined synthetic polymers with simplified molecular interactions to mimic biomolecular self-assembly becomes an excellent approach to understanding the self-assembly mechanism and controlling the process. Peptoid (N-substituted glycine) is a peptidomimetic molecule that exhibits high tunability in molecular interactions through side-chain chemistry and provides a simplified system with no backbone chirality and backbone hydrogen bonds for mechanistic understanding. Here, we report a series of short-sequence amphiphilic peptoids with an anisotropic hydrophobic domain that can self-assemble into flexible lipid-like bilayers. The system adopts rich morphological versatility via subtle solution pH change. Upon annealing, the bilayer 2D sheet structure can be further controlled to stack and twist into 3D helical structures. We combine the molecular dynamics simulation and experimental results to understand the molecular packing and driving forces for the helix-sheet transition. Our system will provide a facile platform to translate peptoid sequences and chemistries into molecular interactions, self-assembly dynamics, and morphologies.