Atomic-level engineering and imaging of polypeptoid crystal lattices

Area of Science:

• Supramolecular chemistry and materials science.
• Polymer science and nanotechnology.

Background:

• Rational design of supramolecular nanomaterials requires atomic-level structural understanding.
• Polypeptoids offer a versatile platform for creating novel nanostructures.

Purpose of the Study:

• To investigate the atomic-level structure and packing of crystalline diblock copolypeptoid nanosheets.
• To understand how chemical modifications, specifically aromatic side-chain substitutions, influence nanosheet geometry.
• To explore the chiral packing in inherently achiral peptoid sequences.

Main Methods:

• Sequence-controlled synthesis of amphiphilic polypeptoids.
• Cryogenic transmission electron microscopy (cryo-TEM) for high-resolution imaging.
• Molecular dynamics simulations to complement experimental observations.

Main Results:

• Formation of free-floating 2D monolayer polypeptoid nanosheets with directly observable polymer chains.
• Visualization of bromine atom side-chain substituents at atomic resolution using cryo-TEM.
• Nanosheet lattice geometry varied with aromatic side-chain para-substitutions, despite conserved backbone conformation.
• Observation of alternating backbone chiralities in rows of peptoid sequences with asymmetric aromatic substitution patterns.

Conclusions:

• Atomic-level insights into peptoid nanosheet crystal structure were achieved.
• Chemical modifications significantly impact nanosheet packing and emergent chirality.
• Findings provide a foundation for designing bioinspired nanomaterials with precise structural control and tunable properties.