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Surface-tethered polymers have been shown to be an efficient lubrication strategy for boundary and mixed lubrication by providing a solvated film between solid surfaces. We have assessed the performance of various graft copolymers as friction modifier additives in oil and revealed important structure-property relationships for this application. The polymers consisted of an oil-soluble, grafted poly(lauryl acrylate) segment and a polar, linear poly(4-acryloylmorpholine) anchor group. Reversible addition-fragmentation chain transfer polymerization was used to access various architectures with control of the grafting density and position of the anchor group. Macrotribological studies displayed promising results with ≈50% reduction in friction coefficient at low polymer treatment rates. QCM-D experiments, neutron reflectometry, small-angle neutron scattering, and atomic force microscopy were used to gather detailed information on these polymers' surface adsorption characteristics, film structure, and solution behavior.

The present study examines the behavior of cyclic peptide polymer conjugates that have been designed to combine their self-assembling ability via H-bonding with the properties of amphiphilic diblock copolymers. Using a combination of asymmetric flow-field flow fractionation (AF 4 ) and small-angle neutron scattering (SANS), we have uncovered unique insight based on the population of structures established at a 24 h equilibrium profile. Our results determine that by introducing a small quantity of hydrophobicity into the conjugated polymer corona, the resulting nanotube structures exhibit low unimer dissociation which signifies enhanced stability. Furthermore, as the hydrophobicity of the polymer corona is increased, the elongation of the nanotubes is observed due to an increase in the association of unimers. This encompasses not only the H-bonding of unimers into nanotubes but also the self-assembly of single nanotubes into segmented-nanotube structures with high aspect ratios. However, this influence relies on a subtle balance between the hydrophobicity and hydrophilicity of the polymer corona. This balance is proposed to determine the solvent entropic penalty of hydrating the system, whereby the cost scales with the hydrophobic quantity. Consequently, it has been suggested that at a critical hydrophobic quantity, the solvation penalty becomes high enough such that the self-assembly of the system deviates from ordered hydrogen bonding. The association behavior is instead dominated by the hydrophobic effect which results in the undesirable formation of disordered aggregates., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

This Review focuses on the establishment and development of self-assemblies governed by the supramolecular interactions between cyclic peptides. The Review first describes the type of cyclic peptides able to assemble into tubular structures to form supramolecular cyclic peptide nanotubes. A range of cyclic peptides have been identified to have such properties, including α-peptides, β-peptides, α,γ-peptides, and peptides based on δ- and ε-amino acids. The Review covers the design and functionalization of these cyclic peptides and expands to a recent advance in the design and application of these materials through their conjugation to polymer chains to generate cyclic peptide-polymer conjugates nanostructures. The Review, then, concentrates on the challenges in characterizing these systems and presents an overview of the various analytical and characterization techniques used to date. This overview concludes with a critical survey of the various applications of the nanomaterials obtained from supramolecular cyclic peptide nanotubes, with a focus on biological and medical applications, ranging from ion channels and membrane insertion to antibacterial materials, anticancer drug delivery, gene delivery, and antiviral applications.

Artificial light-harvesting systems in aqueous media which mimic nature are of significant importance; however, they are often restrained by the solubility and the undesired aggregation-caused quenching effect of the hydrophobic chromophores. Here, we report a generalized strategy toward the construction of efficient artificial light-harvesting systems based on supramolecular peptide nanotubes in water. By molecularly aligning the hydrophobic chromophores along the nanotubes in a slipped manner, an artificial light-harvesting system with a two-step sequential Förster resonance energy transfer process is successfully fabricated, showing an energy transfer efficiency up to 95% and a remarkably high fluorescence quantum yield of 30%, along with high stability. Furthermore, the spectral emission could be continuously tuned from blue through green to orange, as well as outputted as a white light continuum with a fluorescence quantum yield of 29.9%. Our findings provide a versatile approach of designing efficient artificial light-harvesting systems and constructing highly emissive organic materials in aqueous media.

Cyclic peptide-polymer conjugates are capable of self-assembling into supramolecular polymeric nanotubes driven by the strong multiple hydrogen bonding interactions between the cyclic peptides. In this study, we have engineered responsive nanotubes by introducing a cleavable bond that responds to a reductant utilizing pyridyl disulfide reaction chemistry. Reactions between a cysteine containing cyclic peptide (CP-SH) and pyridyl disulfide containing polymers were initially studied, leading to the quantitative formation of cyclic peptide-polymer conjugates. An asymmetric cyclic peptide-polymer conjugate (PEG-CP-S-S- p PEGA) was then synthesized via orthogonal pyridyl disulfide reaction chemistry and NHS coupling chemistry. The disulfide linker formed by the pyridyl disulfide reaction chemistry was then selectively reduced to thiols in the presence of a reductant, enabling the transition of the conjugates from nonassembling unimers to self-assembled supramolecular polymeric nanotubes. It is anticipated that the pyridyl disulfide reaction chemistry will not only enrich the methodology toward the synthesis of cyclic peptide-polymer conjugates, but also lead to the construction of a new family of redox-responsive cyclic peptide-polymer conjugates and supramolecular polymeric nanotubes with tailored structures and functionalities.

Polymer stabilized nanodiscs are self-assembled structures composed of a polymer belt that wraps around a segment of lipid bilayer, and as such are capable of encapsulating membrane proteins directly from the cell membrane. To date, most studies on these nanodiscs have used poly(styrene- co-maleic acid) (SMA) with the term SMA-lipid particles (SMALPs) coined to describe them. In this study, we have determined the physical and thermodynamic properties of such nanodiscs made with two different SMA copolymers. These include a widely used and commercially available statistical poly(styrene- co-maleic acid) copolymer (coSMA) and a reversible addition-fragmentation chain transfer synthesized copolymer with narrow molecular weight distribution and alternating styrene and maleic acid groups with a polystyrene tail, (altSMA). We define phase diagrams for each polymer, and show that, regardless of polymer topological structure, self-assembly is driven by the free energy change associated with the polymers. We also show that nanodisc size is polymer dependent, but can be modified by varying polymer concentration. The thermal stability of each nanodisc type is similar, and both can effectively solubilize proteins from the E. coli membrane. These data show the potential for the development of different SMA polymers with controllable properties to produce nanodiscs that can be optimized for specific applications and will enable more optimized and widespread use of the SMA-based nanodiscs in membrane protein research.