Hierarchical assembly of peptoids on MoS2

Bio-macromolecular assembly forms intricate scaffolds in living systems that allow them to biomineralize bone, enamel, and shell. Such bioinspired approaches have also been widely used in biohybrid materials synthesis. Recently, researchers have demonstrated functional bioelectronic structures by assembling biopolymers, including proteins and peptides, on van der Waals (VdW) materials for sensors and energy storage and harvesting. However, the hierarchical assembly of biopolymers on VdW materials has yet to be fully documented, because modulating the assembly architectures by controlling the energy landscape along with environmental stimuli, in which various assembly phases occur, remains challenging. In this study, we focused on peptoids, biomimetic polymers with properties similar to peptides but offering advantages such as greater side chain diversity, lower complexity due to elimination of backbone-backbone hydrogen binding, lower synthesis costs, and improved stability. Specifically, we designed two short peptoid sequences capable of assembling on MoS2. Our findings reveal diverse self-assembled phases, including monolayer hybrid films with high crystallinity, vesicle-like nanoparticles, lamellae, and multi-layer ribbons. We elucidated the assembly processes of these states and confirmed the occurrence of phase transitions between them by using in situ atomic force microscopy (AFM). The results highlight the critical roles of peptoid-peptoid, peptoid-solvent, and peptoid-MoS2 interactions. These insights significantly advance the understanding needed to design hierarchical biopolymer architectures at VdW material-solvent interfaces with potential implications for enhancing the performance of bioelectronic devices based on 2D vdW materials.