Structure-Determining Step in the Hierarchical Assembly of Peptoid Nanosheets

Abstract

Organic two-dimensional nanomaterials are of growing importance, yet few general synthetic methods exist to produce them in high yields and to precisely functionalize them. We previously developed an efficient hierarchical supramolecular assembly route to peptoid bilayer nanosheets, where the organization of biomimetic polymer sequences is catalyzed by an air-water interface. Here we determine at which stages of assembly the nanoscale and atomic-scale order appear. We used X-ray scattering, grazing incidence X-ray scattering at the air-water interface, electron diffraction, and a recently developed computational coarse-grained peptoid model to probe the molecular ordering at various stages of assembly. We found that lateral packing and organization of the chains occurs during the formation of a peptoid monolayer, prior to its collapse into a bilayer. Identifying the structure-determining step enables strategies to influence nanosheet order, to predict and optimize production yields, and to further engineer this class of material. More generally, our results provide a guide for using fluid interfaces to catalytically assemble 2D nanomaterials.

Implicit-Solvent Coarse-Grained Simulation with a Fluctuating Interface Reveals a Molecular Mechanism for Peptoid Monolayer Buckling

“…The direction of buckling of peptoid monolayers has not been measured in experiments, and the only structural measurements, grazing-incidence X-ray scattering, yielded isotropic scattering spectra due to the wide beams (apparently wider than the correlation length for the monolayer orientation) needed to collect data. 3 One outstanding question is why the block-28 peptoids buckle so easily in the simulations. For all surface pressures high enough to keep the monolayer in a single condensed phase (rather than opening voids), the block-28 monolayers buckle at every available row of termini.…”

Polypeptoid polymers: Synthesis, characterization, and properties

“…As a result, the global conformations of polypeptoids are strongly dependent on the N-substituent structures, giving rise to random coils or well-defined secondary structures [eg, polyproline I (PPI) helix [1][2][3][4][5][6] and R-sheets] [7][8][9][10][11][12] that are reminiscent of those of polypeptides. The polypeptoid backbone containing tertiary amide linkages is highly polar and hydrophilic.…”

“…The polypeptoid backbone containing tertiary amide linkages is highly polar and hydrophilic. The physicochemical properties of polypeptoids can be tailored by the N-substituent structures, enabling control over the hydrophilicity and lipophilicity balance (HLB), charge characteristics, [13,14] backbone conformation, [1][2][3][4][5][6][7][8][9][10][11][12] solubility, [15][16][17][18][19][20] thermal and crystallization properties of the polypeptoids. [21][22][23][24] Without extensive hydrogen bonding, polypeptoids are thermally processable similar to conventional thermoplastics, [20][21][22][23][24] whereas polypeptides undergo thermal degradation before they can be melt-processed due to the extensive hydrogen bonding interactions.…”

Nanowire Oriented On-Surface Growth of Chiral Cystine Crystalline Nanosheets

“…19-26 2D molecular crystals are important class of 2D nanomaterials due to their abundant species and adjustable architectures, which are the keys to tailor their structures and chemical functionalities. [27][28][29][30][31][32][33] The exploration of a new route to achieve the controlled growth of 2D molecular crystals is thus of scientific significance and highly desired.…”