Shaken, Not Stirred: Collapsing a Peptoid Monolayer To Produce Free-Floating, Stable Nanosheets

Abstract

Two-dimensional nanomaterials play a critical role in biology (e.g., lipid bilayers) and electronics (e.g., graphene) but are difficult to directly synthesize with a high level of precision. Peptoid nanosheet bilayers are a versatile synthetic platform for constructing multifunctional, precisely ordered two-dimensional nanostructures. Here we show that nanosheet formation occurs through an unusual monolayer intermediate at the air-water interface. Lateral compression of a self-assembled peptoid monolayer beyond a critical collapse pressure results in the irreversible production of nanosheets. An unusual thermodynamic cycle is employed on a preparative scale, where mechanical energy is used to buckle an intermediate monolayer into a more stable nanosheet. Detailed physical studies of the monolayer-compression mechanism revealed a simple preparative technique to produce nanosheets in 95% overall yield by cyclical monolayer compressions in a rotating closed vial. Compression of monolayers into stable, free-floating products may be a general and preparative approach to access 2D nanomaterials.

Polypeptoid polymers: Synthesis, characterization, and properties

“…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.…”

“…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.…”

Improved chemical and mechanical stability of peptoid nanosheets by photo-crosslinking the hydrophobic core

“…1d and e). 19,20 In particular, the chloro substituted monomer was selected over the more labile Ar-halides (e.g. Ar-Br or Ar-I) due to its smaller size and lower hydrophobicity.…”

“…17,27 Nanosheets were then formed in aqueous solution (at 20 mm peptoid concentration) via the vial rocking method. 20,27 Nanosheet crosslinking was achieved by exposing a 4 mL glass open vial containing 500 mL (5 mm deep solution) of 20 mM peptoid nanosheet solution to 254 nm UV light for up to 3 hours (see ESI † for details). The extent of nanosheet crosslinking reaction was monitored both by polyacrylamide gel electrophoresis (PAGE) analysis (typically used for proteins), to follow the increase in molecular weight of the peptoid chains, as well as by Raman spectroscopy to follow the conversion of functional groups, from chlorophenyl to biphenyl.…”

Free‐Standing Gold‐Nanoparticle Monolayer Film Fabricated by Protein Self‐Assembly of α‐Synuclein

“…Concerning the preparation of two-dimensional (2D) nanomembranes, various substances other than NPs, such as carbon, [6] surfactant of dodecylphosphocholine, [7] organic-inorganic composite, [8] and peptoid [9] have also been employed to fabricate the functional membranes valuable for the development of optical and electronic devices and membrane systems. [10] Herein, a bio-based strategy is introduced to produce a free-floating ultrathin AuNP sheet where AuNPs are tightly packed in a monolayer by employing a self-associative protein of a-synuclein (aS) as a binding agent.…”