β-Sheet forming self assembling cyclic peptides offer a versatile scaffold for the construction and control of hydrogen-bonded nanotube assemblies. These structures have major advantages over other nanoscale tubular structures, including sub-nanometer control over the internal diameter, and the ability to control internal and external chemical functionality. This Tutorial Review presents an overview of nanotubes derived from this class of cyclic peptides. The design rationale for functional nanotubes based on cyclic peptide ring size and chemical functionality is discussed. Additionally, we highlight the recent expansion of the nanotube toolbox through conjugation of (macro)molecules to the cyclic peptides. These provide additional functionality and control nanotube dimensions that could potentially prove beneficial in future applications.
We describe the solution assembly of polymer-cyclic peptide conjugates into nanotubes, by direct in situ measurements. The conjugates were assembled by exploiting the b-sheet assembly of the alt(D,L) cyclic octapeptide core. The conjugated polymer permits solubilization of the peptide and the resulting nanotubes, thus allowing for the first time the direct study of the assembly mechanism of this system.The resulting materials present unique properties for a wide range of applications. We find that the polymer can act to both shield the peptide core from the solvent and to put strain on the peptide core through steric repulsions. By controlling both the solvent mixture and the length of the polymer, control over the length of the resulting nanotubes can be obtained. In addition, monitoring the assembly with temperature allows the strength of the assembly to be probed, adding evidence for a co-operative mechanism of assembly. Finally, selective deuteration of the polymer component in SANS analyses leads to the precise measurement of the nanotubes core dimensions, and by cross-linking the polymeric shell, the structure of the nanotubes in solution are confirmed by transmission electron microscopy (TEM).This study establishes the fundamentals needed for the design and control of these new materials.
Stratified coatings are used to provide properties at a surface, such as hardness or refractive index, which are different from underlying layers. Although time-savings are offered by self-assembly approaches, there have been no methods yet reported to offer stratification on demand. Here, we demonstrate a strategy to create self-assembled stratified coatings, which can be switched to homogenous structures when required. We use blends of large and small colloidal polymer particle dispersions in water that self-assemble during drying because of an osmotic pressure gradient that leads to a downward velocity of larger particles. Our confocal fluorescent microscopy images reveal a distinct surface layer created by the small particles. When the pH of the initial dispersion is raised, the hydrophilic shells of the small particles swell substantially, and the stratification is switched off. Brownian dynamics simulations explain the suppression of stratifi-cation when the small particles are swollen as a result of reduced particle mobility, a drop in the pressure gradient, and less time available before particle jamming. Our strategy paves the way for applications in antireflection films and pro-tective coatings in which the required surface composition can be achieved on demand, simply by adjusting the pH prior to deposition
This work reports on a facile approach to the synthesis of highly branched polymers by the homopolymerization of commercially available divinyl benzene (DVB) via reversible additionÀ fragmentation chain transfer (RAFT) polymerization. The presence of RAFT agents allows conversions as high as 68% before crosslinking, instead of 15% for conventional free radical polymerization (FRP). The study extends this new approach by synthesizing starlike block copolymers of methyl acrylate (MA) and DVB by exploiting the living characteristic offered by RAFT polymerization. The resulting highly branched DVB polymers are used to produce in situ cross-linked polymeric particles following thermal stimuli. In addition, we exploit the large number of residual double bonds in the highly branched p(DVB) to further functionalize the polymer via thiolÀene click chemistry.
Nanoparticles of cerium dioxide (or nanoceria) are of interest because of their oxygen buffering, photocatalytic ability, and high UV absorption. For applications, the nanoceria can be incorporated in a polymer binder, but questions remain about the link between the nanoparticle distribution and the resulting nanocomposite properties. Here, the thermal, mechanical and optical properties of polymer/ceria nanocomposites are correlated with their nanostructures. Specifically, nanocomposites made from waterborne Pickering particles with nanoceria shells are compared to nanocomposites made from blending the equivalent surfactant-free copolymer particles with nanoceria. Two types of nanoceria (protonated or citric acid-coated) are compared in the Pickering particles. A higher surface coverage is obtained with the protonated ceria, which results in a distinct cellular structure with nanoceria walls within the nanocomposite. In the blend of particles, a strong attraction between the protonated nanoceria and the acrylic acid groups of the copolymer likewise leads to a cellular structure.This structure offers transparency in the visible region combined with strong UV absorption, which is desired for UV blocking coating applications. Not having an attraction to the polymer, the citric acidcoated nanoceria forms agglomerates that lead to undesirable light scattering in the nanocomposite and yellowing. This latter type of nanocomposite coating is less effective in protecting substrates from UV Published in ACS Applied Nano Materials (2018) 2 damage but provides a better barrier to water. This work shows how the nanoparticle chemical functionalization can be used to manipulate the structure and to tailor the properties of UV-absorbing barrier coatings.
Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. AbstractWe present a fundamental study into the self-assembly of (cyclic peptide)-polymer conjugates as a versatile supramolecular motif to engineer nanotubes with defined structure and dimensions, as characterised in solution using small angle neutron scattering (SANS).This work demonstrates the ability of the grafted polymer to stabilise and/or promote the formation of unaggregated nanotubes by the direct comparison to the unconjugated cyclic peptide precursor. This ideal case permitted a further study into the growth mechanism of self-assembling cyclic peptides, allowing an estimation of the cooperativity. Furthermore we show the dependency of the nanostructure on the polymer and peptide chemical functionality in solvent mixtures that vary in the ability to compete with the intermolecular associations between cyclic peptides and ability to solvate the polymer shell.
This article provides an overview of the outcomes of a European-funded project called BarrierPlus. A new type of water-based barrier coating was developed for structural steel applications. Advantages of this coating include enhanced moisture resistance, low volatile organic compounds (VOCs), and one-component self-crosslinking free of isocyanates. To enable this performance, a latex polymer binder was uniquely designed without using soaplike molecules, known as surfactants, to form the dispersion. By minimizing surfactants in the coating, the barrier properties were significantly enhanced. The latex was successfully scaled up to 15 kg quantities by an SME, coatings formulations were scaled to pilot quantities, and a variety of characterization and coatings performance tests were completed. A life cycle assessment found that the BarrierPlus coating has a better environmental profile than an Manuscript submitted to Steel Construction industry benchmark solvent-borne coating and showed promising results relative to commercial waterborne benchmarks.
We report the synthesis and assembly of (N-methylated cyclic peptide)-polymer conjugates for which the cyclic peptide is attached to either the α- or both α- and ω- end groups of a polymer. A combination of chromatographic, spectroscopic, and scattering techniques reveals that the assembly of the conjugates follows a two-level hierarchy, initially driven by H-bond formation between two N-methylated cyclic peptides, followed by unspecific, noncovalent aggregation of this peptide into small domains that behave as branching points and lead to the formation of branched supramolecular polymers.
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