ACS Macro Letters最新文献

Supramolecular polymeric nanotubes based on the self-assembling cyclic peptide–polymer conjugates are a promising class of materials, showing great potential in various biological applications. Herein, we present a novel strategy to promote nanotube assembly through effectively shielding the cyclic peptides from water, via the introduction of varying hydrophobic groups. As determined by a combination of SANS, TEM, and SLS, hydrophobic interactions, π–π stacking, and multiple hydrogen bonding interactions cooperate in the self-assembly of the cyclic peptide–polymer conjugates, allowing for the construction of supramolecular nanotubes that are longer than expected in water. This approach offers an effective pathway toward the design of organic nanotubes of hundreds of nanometers in water.

Molecular fabrics with fascinating physical characteristics, such as structural flexibility and single-layered thinness, have attracted much attention. Chemists worldwide have been working on building unique molecularly woven structures in two dimensions. However, the synthesis of two-dimensional molecular weaving remains a challenging task, especially in water. Herein, we propose a straightforward and practical method to construct 2D molecular fabrics by enzymatically covalent and noncovalent syntheses in water. In particular, aromatic helical pentamers with two-terminal tyrosine residues (Penta-Tyr) can spontaneously dimerize via π-π interactions into double-helical interlocking structure, and the two-terminal tyrosine moieties of Penta-Tyr can undergo oxidative polymerization catalyzed by horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂) for effective covalent cross-linking. The 2D monolayered molecular fabrics can be readily prepared by the catalysis of HRP and H₂O₂ under mild conditions, which exhibit concentration-dependent weaving behavior. This work not only demonstrates an enzyme-catalyzed approach for the highly efficient synthesis of 2D monolayered molecular fabrics for the first time but also will promote the controllable preparation and application of water-soluble 2D molecular fabrics.

Sequence-controlled polymerization aims to bridge the gap between biopolymers and synthetic macromolecules. In a kinetically controlled approach, the inherent reactivity differences among monomers determine the primary structure or sequence of the monomers linked within the resulting copolymer chains. This report outlines a one-pot synthesis of polypeptide-b-polypeptoid by choosing a suitable pair of N-carboxy anhydride (NCA) monomers with significant reactivity differences. We have demonstrated the preparation of well-defined block copolymers, including polyproline-b-polysarcosine (PLP-b-PSar) and poly(propargyl proline)-b-polysarcosine (PLPP-b-PSar) in a single step. ¹H NMR kinetic studies confirmed the sequence-controlled primary structures of these block copolymers. The NMR analysis indicated a striking reactivity ratio difference (r_PLP = 925 and r_PSar = 0.0014; r_PLPP = 860 and r_PSar = 0.0015) between the selected monomer pairs, which was crucial for a one-pot block copolymer synthesis. Notably, these sequence-controlled copolymers' secondary structures and stability were remarkably similar to those of block copolymers synthesized through conventional sequential addition methods. This further underscores the practicality of this kinetically controlled approach.

Understanding the dynamics of nanosheets in polymer matrices is crucial for the processing of polymer nanocomposites and their applications in drug delivery. In this work, we investigate the diffusion of thin nanosheets in unentangled polymer melts using molecular dynamics simulations. We show that for nanosheets smaller than a characteristic size l_c, which is a few times the polymer chain size, the continuum hydrodynamic theory based on macroscopic viscosity breaks down and significantly underestimates the diffusion coefficients. For nanosheets with sizes l < l_c, we derive scaling relationships for both translational and rotational diffusion coefficients as functions of l and further reveal the dynamical coupling between nanosheet motion and the modes of the polymer melt. For l > l_c, the continuum theory is recovered. Our findings reconcile the continuum and scaling theories for the diffusion of nanoparticles in polymer melts.

The oxidative coupling of amines is a useful way to prepare many diverse compounds for the pharmaceutical and chemical industries. Covalent organic frameworks (COFs), a crystalline class of porous polymers, have emerged as promising heterogeneous photocatalysts that can accomplish this transformation under metal-free conditions due to their excellent photochemical stability and tunable electronic properties. Herein, we report the optoelectronic and photocatalytic properties of an olefin-linked COF containing thienothiophene (TT) and 2,4,6-trimethyl-1,3,5-triazine (TMT) units. The TT-TMT-COF exhibited a narrow band gap with extended light absorption and excellent charge separation, making it useful for the oxidative coupling of various benzylamines. The TT-TMT-COF exhibited fast reaction times, excellent recyclability, and conversions as high as ∼99%. The reactivity of TT-TMT-COF was on par or significantly better than that of a few small molecule 2,4,6-tris((E)-2-(thieno[3,2-b]thiophen-2-yl)vinyl)-1,3,5-triazine (TT-TMT) and 2,4,6-tris((E)-2-(thiophen-2-yl)vinyl)-1,3,5-triazine (Thio-TMT) homogeneous catalytic systems containing similar functional units. This work further highlights the ability of the COF to perform useful and efficient catalytic transformations in a sustainable manner.

Achiral dynamic helical polymers, poly(quinoxaline-2,3-diyl)s (P1 and P2) bearing achiral carboxylic acid side chains, i.e., carboxymethoxymethyl (in P1) and carboxyethoxymethyl (in P2), with different polymerization degrees were synthesized. They exhibited induced circular dichroism (ICD) in the presence of chiral amines such as 1-phenylethylamine and nicotine, 1,2-amino alcohols such as valinol, leucinol, and prolinol, and the basic amino acid, arginine, in response to the induction of right- or left-handed helical conformation. The efficiency of helix induction depends on the compatibility of the structures of amines and polymers, with no clear structural correlation. The highly sensitive and formulated nature of ICD with the helical polymer-based poly(carboxylic acid)s allowed their use as CD-based sensors to detect and quantify minute imbalances of the enantiomeric excess of chiral molecules. We determined 0.2%–0.6% ee in the commercially available 1-phenylethylamine from three different suppliers, which have the label of “dl” or no indication of enantiopurity using P1 as a chemosensor.