SANS profiles of AOT–SiC water-in-oil microemulsions in various solvents are provided.

Helicity is a fundamental structural principle that imparts order and function to biological systems, with many biological assemblies exhibiting helical architectures that often emerge and mature dynamically over time, enabling adaptive structural transformations and functional regulation. Nonetheless, examples of synthetic supramolecular polymers in which helicity arises dynamically from kinetically trapped, nonhelical structures remain rare. Here we report a chlorophyll-based supramolecular polymer that undergoes a spontaneous, sequential, multistep conversion from nonhelical fibers to helical architectures. Chlorophyll derivatives bearing barbituric acid hydrogen-bonding sites first assemble into hexameric rosettes, which then kinetically stack to yield metastable, nonhelical fibers. Over time these fibers evolve through three discrete stages into helically twisted structures, each characterized by a progressive tightening of the helical pitch. Because the rosette comprises six highly aggregative chlorophyll chromophores─each bearing multiple stereocenters and peripheral side chains─its structural complexity prevents rapid adoption of a single, globally stable stacking conformation. Instead, the assembly traverses a rugged energy landscape, proceeding in a sequential, stepwise, discontinuous manner through a series of local minima toward more stable arrangements. This multistep transformation was elucidated by UV/vis absorption, circular dichroism (CD), atomic force microscopy (AFM), and small-angle scattering (SAS) techniques. Kinetic analysis with a cooperative model further revealed that cooperative structural transitions, in which adjacent helical units promote additional helicity, play a pivotal role in this process. Strikingly, in the tightest helical state the supramolecular chirality observed by AFM is opposite to that derived from chiral chlorophyll stacking inferred from CD spectroscopy. This discrepancy is consistent with the creeper-helix model, in which an offset in the chromophore stack inverts the CD response, as suggested by spectral calculations based on an exciton model. Taken together, these results indicate that the stepwise tightening of the helical pitch is driven by an increasing translational offset between stacked rosette units. Thus, even one-dimensional supramolecular polymers can undergo cooperative, crystal-phase-transition-like structural reorganizations.

With a Gemini surfactant architecture and cationic 4-aminopyridinium headgroups, octenidine dihydrochloride (OCT) is one of the most potent antimicrobial actives. However, how its unique molecular architecture orchestrates interactions with lipopolysaccharides (LPS), a major constituent of the Gram-negative bacteria outer membrane, is not well understood. To probe OCT-LPS molecular interactions, we have studied the morphology and structure of nanoaggregates co-assembled between OCT and LPS. Furthermore, OCT was compared with Alkyl 8-10-8, an architecturally analogous Gemini surfactant with quaternary ammonium headgroups. Small-angle neutron scattering (SANS) revealed that, upon addition of 1.2 CMC OCT in the presence of 2.5 mM Ca2+, worm-like LPS-smooth micelles (of a radius ∼11.8 nm and a length ∼300 nm) transformed into longer rods with an ellipsoidal cross-section (9.4 nm × 29.3 nm) up to 3 µm in length. In contrast, co-assembly with 1.2 CMC Alkyl 8-10-8 led to a nano-aggregate mixture of lamellae and globules. Complementary cryo-TEM, dynamic light scattering, and zeta potential measurements further informed on the LPS-Gemini co-assembled nanostructures. To reconcile these observations, we suggest that the 4-aminopyridinium headgroups of OCT bind to anionic Lipid A phosphates in LPS through electrostatic, H-bonding, and π-system interactions, displacing bridging Ca2+ ions. In contrast, the dimethylammonium headgroups of Alkyl 8-10-8 would undergo dynamic exchange with the Ca2+ bridging between Lipid A phosphates, instead of binding to Ca2+, evident from disintegration of the worm-like aggregates. These findings provide mechanistic insights into the molecular interactions mediated by the OCT architecture, underpinning binding and subsequent disruption of the LPS-rich outer membrane leaflet in Gram-negative bacteria, with implications to future rational design of antimicrobial agents.

Carbon nanomaterials composite is often made with the aid of ionic surfactants to provide stable system. Despite the existing literatures, there is still lack of consensus regarding the surfactant design, aggregation structure, and corresponding dispersion quality. Here, cellulose conductive papers were prepared by combining multi-walled carbon nanotubes (MWCNTs) dispersion stabilized by ionic surfactants and/or anionic surfactant ionic liquids (SAILs) with nanofibrillated Kenaf (Hibiscus cannabinus L.) cellulose fiber. The SAILs were systematically synthesized from commercial surfactants sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS) combined with a 1-butyl-3-methyl-imidazolium (BMIM) cation. The efficiency of each compound was measured in terms of the nanocomposite papers electrical conductivities. The SAILs promoted similar to 6 orders of magnitude enhancement compared to composite papers without stabilizer. Field emission scanning electron microscopy (FESEM) revealed more individualized nanotubes when SAILs were present. The results highlight the importance of surfactant design in achieving optimal dispersion and performance in carbon nanomaterials composites.

Mixtures of the zwitterionic surfactant TDMAO and the anionic surfactant LiPFOS spontaneously self-assemble into well defined vesicles. The size of these vesicles is determined by the ratio of bending rigidity and line tension. By partially charging TDMAO, and thereby moving more to a catanionic system, the size of these vesicles can be controlled. Using stopped flow small angle neutron scattering we monitor the kinetics of vesicle formation and obtain their final size. Neutron spin echo spectroscopy allows for an independent measurement of the vesicle's bending rigidity. Combining this bending rigidity with the radius of newly formed vesicles, which is determined by the ratio of bending rigidity and line tension, we can determine the line tension. We find that it is the line tension that controls the trend in size of the vesicles. In summary, this means that here one has a surfactant mixture that delivers well-defined vesicles, whose size is controlled by the electrostatic interactions of the head groups.

Steric complementarity plays an essential role in maintaining protein architecture and recognition. In supramolecular chemistry and material science, however, it remains a major challenge to precisely control steric complementarity and associated interactions across different length scales for the construction of higher-order peptide and protein nanostructures and nanomaterials. Through coassembly of designed aromatic short peptide stereoisomers, we here incorporate specific π-π stacking interactions into facial complementarity between peptide strands within a β-sheet in a controllable manner. The high steric complementarity between aromatic side chains leads to strong coassembly capabilities of these peptide stereoisomers and dramatic changes in supramolecular morphology and size. We also unravel suprastructural handedness codes for their coassemblies and relate them to the side chain geometric complementarity and distribution on the two faces of the β-sheet. This work not only highlights the importance of steric complementarity in peptide folding but also provides a paradigm for the fabrication of intricate peptide β-sheet assemblies via steric complementarity at the subsheet level.

Earlier studies demonstrated the ability of some fluorinated surfactants to form rod-like reverse micelles with the ability to thicken water/supercritical CO2 (scCO(2)) mixtures at temperatures below 45 degree celsius [Langmuir 26 (2010) 83-88. Soft Matter 8 (2012) 7044-7055. Colloids and Surfaces B, 168 (2018), 201-210.]. Such viscosity enhancement of scCO(2) is known to increase sweep efficiency for oil recovery with CO2 flooding. However, temperatures of up to similar to 100 degree celsius in conventional reservoirs are much higher than those employed in laboratory studies, and tend to weaken inter- and intra-molecular interactions between surfactant molecules, discouraging rod-like reverse micelle formation. With the aim of designing surfactants which form rod-like reverse micelles and thicken CO2 at high temperatures, this study examined phase behavior, nanostructures of reverse micelles and thickening ability of double omega-hydroperfluorocarbon-tail anionic surfactants in W/scCO(2) mixtures at temperatures of 35 - 75 degree celsius and pressure of 80 - 400 bar with different water-to-surfactant molar ratios (W-0). The measured CO2 viscosity increased by 1.9-2.2 x for double-chain surfactants M(di-HCF6)(x) (counterion Mx+ = Ni2+ and Co2+) at 40 mM, over the experimental temperature range. On the other hand, the shorter chain H(CF2)(4)CH2 twin-tail surfactants M(di-HCF4)(x) and Na(di-HCF6) gave only 1.1-1.5 x viscosity enhancements. The maximum thickening ability of M(di-HCF6)(2) was at W-0 = 10 in the W-0 range of 5-20 75 degree celsius and 350 bar. High pressure and high temperature small-angle neutron scattering (SANS) was used determine the micellar structure in these systems, and rod micelles of aspect ratios of 4.5-6.5 were found. The results clearly suggest that omega-hydroperfluorohexyl-tails and divalent counterions induce the formation of rod-like reverse micelles in W/CO2 mixtures, even at high temperatures commensurate with in-reservoir conditions.

In this work, electrochemically exfoliated graphene oxide-based photocatalyst was synthesised with the help of single- (sodium dodecyl sulphate; SDS) and triple-chain (sodium 1,4-bis(neopentyloxy)-3-(neopentylcarbonyl)-1,4-dioxobutane-2-sulfonate; TC14) anionic surfactants. The hybrid photocatalyst is a system consisting of surfactant-assisted electrochemically exfoliated graphene oxide (sEGO) and zinc oxide (ZnO). The system was prepared by exfoliating graphite in the presence of surfactant and ZnO, and it was used for the removal of methylene blue (MB) dye. Of these different surfactants, the triple-chain TC14 exhibited 98.53% MB removal, which was significantly higher than the system with SDS surfactant (50.94%) or ZnO alone (42.33%). Observations through field-emission scanning electron microscopy suggested an enhanced exfoliation degree upon increasing the number of surfactant chains. Results from zeta potential measurement also revealed increased system stability along with a high number of surfactant chains and the addition of ZnO into the system. These findings highlight the importance of tailoring the surfactant’s chemical structure to achieve enhanced graphene oxide-based photocatalyst performance for MB dye removal and wastewater treatment.

As part of an ongoing study of the structure and properties of mixtures of ionic liquids in which one component has a hydrocarbon chain and the other a semiperfluorocarbon chain, we now report a study of the mixtures [C8MIM]1-x[C10MIM-F17]x[Tf2N], [C10MIM]1-x[C8MIM-F13]x[Tf2N] and [C10MIM]1-x[C10MIM-F17]x[Tf2N], where [C8MIM][Tf2N] is 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide, [C10MIM][Tf2N] is 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C8MIM-F13][Tf2N] is 1-(1H,1H,2H,2H-perfluorooctyl)-3-methylimidizolium bis(trifluoromethylsulfonyl)imide and [C10MIM-F17][Tf2N] is 1-(1H,1H,2H,2H-perfluorodecyl)-3-methylimidizolium bis(trifluoromethylsulfonyl)imide. The mixtures were investigated using small-angle X-ray (SAXS) and neutron (SANS) scattering complemented by molecular dynamics simulations (with viscosity and surface tension measurements also possible for the mixtures [C10MIM]1-x[C8MIM-F13]x[Tf2N]). Unlike previous studies of [C8MIM]1-x[C8MIM-F13]x[Tf2N], where no strong evidence of alkyl/fluoroalkyl chain segregation or triphilic behaviour was seen (Elstone et al., J. Phys. Chem. B, 2023, 127, 7394-7407), these new mixtures show the formation of small aggregates of varying sizes of each component, even though all were co-miscible across the full range of compositions. Thus, while a clear polar non-polar peak (PNPP) was observed at large or small values of x, at intermediate compositions the small-angle neutron scattering at low q was dominated by scattering from these small aggregates, while at other compositions, there was little or no evidence of the PNPP. The origins of this behaviour are discussed in terms of inter-chain interactions. The ionic liquids [C10MIM][Tf2N] and [C10MIM-F17][Tf2N] are miscible in all proportions, but scattering studies and MD calculations show the formation of small aggregates. These data are discussed relative to hydrocarbon/fluorocarbon miscibility.

SmallVolume 20, Issue 5 2470043 Back CoverFree Access Controlling 1D Nanostructures and Handedness by Polar Residue Chirality of Amphiphilic Peptides (Small 5/2024) Hai Xu, Hai Xu State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorKai Qi, Kai Qi State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorCheng Zong, Cheng Zong State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorJing Deng, Jing Deng National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071 ChinaSearch for more papers by this authorPeng Zhou, Peng Zhou State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 China State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Science, Beijing, 100190 ChinaSearch for more papers by this authorXuzhi Hu, Xuzhi Hu Biological Physics Group, Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL UKSearch for more papers by this authorXiaoyue Ma, Xiaoyue Ma State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorDong Wang, Dong Wang State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorMuhan Wang, Muhan Wang Department of Civil Engineering, Qingdao University of Technology, Qingdao, 266033 ChinaSearch for more papers by this authorJun Zhang, Jun Zhang School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266033 ChinaSearch for more papers by this authorStephen M. King, Stephen M. King ISIS Pulsed Neutron & Muon Source, Didcot, Oxon, OX11 0QX UKSearch for more papers by this authorSarah E. Rogers, Sarah E. Rogers ISIS Pulsed Neutron & Muon Source, Didcot, Oxon, OX11 0QX UKSearch for more papers by this authorJian Ren Lu, Jian Ren Lu Biological Physics Group, Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL UKSearch for more papers by this authorJun Yang, Jun Yang National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071 ChinaSearch for more papers by this authorJiqian Wang, Jiqian Wang State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this author Hai Xu, Hai Xu State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorKai Qi, Kai Qi State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorCheng Zong, Cheng Zong State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorJing Deng, Jing Deng National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071 ChinaSearch for more papers by this authorPeng Zhou, Peng Zhou State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 China State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Science, Beijing, 100190 ChinaSearch for more papers by this authorXuzhi Hu, Xuzhi Hu Biological Physics Group, Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL UKSearch for more papers by this authorXiaoyue Ma, Xiaoyue Ma State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorDong Wang, Dong Wang State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this authorMuhan Wang, Muhan Wang Department of Civil Engineering, Qingdao University of Technology, Qingdao, 266033 ChinaSearch for more papers by this authorJun Zhang, Jun Zhang School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266033 ChinaSearch for more papers by this authorStephen M. King, Stephen M. King ISIS Pulsed Neutron & Muon Source, Didcot, Oxon, OX11 0QX UKSearch for more papers by this authorSarah E. Rogers, Sarah E. Rogers ISIS Pulsed Neutron & Muon Source, Didcot, Oxon, OX11 0QX UKSearch for more papers by this authorJian Ren Lu, Jian Ren Lu Biological Physics Group, Department of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL UKSearch for more papers by this authorJun Yang, Jun Yang National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071 ChinaSearch for more papers by this authorJiqian Wang, Jiqian Wang State Key Laboratory of Heavy Oil Processing and Department of Biological and Energy Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580 ChinaSearch for more papers by this author First published: 01 February 2024 https://doi.org/10.1002/smll.202470043AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Peptide Supramolecular Handedness In article number 2304424, Hai Xu, Jun Yang, Jiqian Wang, and co-workers report how changing the chirality of the terminal charged residues of an amphiphilic hexapeptide sequence Ac-I4K2-NH2 gives rise to distinct nanostructures and supramolecular handedness. The formation of wide nanotubes arises from the co-assembly of right- and left-handed β-strands while thin, right-handed twisted nanofibrils are formed by the assembly of left-handed β-strands. Volume20, Issue5February 1, 20242470043 RelatedInformation

Photosynthetic bacteria have evolved highly efficient light-harvesting systems by organizing chlorophyll (Chl) pigments into circular and tubular supramolecular arrays. To construct these surapmoelcular Chl arrays from the same molecular design, we synthesized two hydrogen-bonding chlorins using natural Chl-a as the starting material: free-base chlorin functionalized with hydrogen-bonding barbituric acid and second- or third-generation alkyl dendrons (G2 and G3, respectively). The barbituric acid moiety promotes the formation of a hydrogen-bonded cyclic hexamer known as rosette. In chloroform, both the synthetic Chl-a derivatives formed rosettes; however, in methylcyclohexane as a low-polarity solvent, the G2-dendron chlorin formed columnar structures by stacking rosettes, while the G3-dendron chlorin formed disc-shaped particles. AFM revealed the formation of extended helical fibers for the former and homogeneous nanoparticles, possibly single rosettes, for the latter. These results suggest that the third-generation of the dendron can inhibit the stacking of rosettes, leading to the formation of two distinct types of chlorin aggregates: circular and tubular.

Self-sorting in functionalized dipeptide systems can be driven by the chirality of a single amino acid, both at a high pH in the micellar state and at a low pH in the gel state. The structures formed are affected to some degree by the relative concentrations of each component showing the complexity of such an approach. The structures underpinning the gel network are predefined by the micellar structures at a high pH. Here, we describe the systems prepared from two dipeptide-based gelators that differ only by the chirality of one of the amino acids. We provide firm evidence for self-sorting in the micellar and gel phases using small-angle neutron scattering and cryo-transmission electron microscopy (cryo-TEM), showing that complete self-sorting occurs across a range of relative concentrations.

Peptide assemblies are promising nanomaterials, with their properties and technological applications being highly hinged on their supramolecular architectures. Here, how changing the chirality of the terminal charged residues of an amphiphilic hexapeptide sequence Ac-I4 K2 -NH2 gives rise to distinct nanostructures and supramolecular handedness is reported. Microscopic imaging and neutron scattering measurements show thin nanofibrils, thick nanofibrils, and wide nanotubes self-assembled from four stereoisomers. Spectroscopic and solid-state nuclear magnetic resonance (NMR) analyses reveal that these isomeric peptides adopt similar anti-parallel β-sheet secondary structures. Further theoretical calculations demonstrate that the chiral alterations of the two C-terminal lysine residues cause the formation of diverse single β-strand conformations, and the final self-assembled nanostructures and handedness are determined by the twisting direction and degree of single β-strands. This work not only lays a useful foundation for the fabrication of diverse peptide nanostructures by manipulating the chirality of specific residues but also provides a framework for predicting the supramolecular structures and handedness of peptide assemblies from single molecule conformations.

The rational design of lipid nanoparticles (LNPs) for enhanced gene delivery remains challenging because of incomplete knowledge of their formulation-structure relationship that impacts their intracellular behavior and consequent function. Small-angle neutron scattering has been used in this work to investigate the structure of LNPs encapsulating plasmid DNA upon their acidification (from pH 7.4 to 4.0), as would be encountered during endocytosis. The results revealed the acidification-induced structure evolution (AISE) of the LNPs on different dimension scales, involving protonation of the ionizable lipid, volume expansion and redistribution of aqueous and lipid components. A similarity analysis using an LNP's structural feature space showed a strong positive correlation between function (measured by intracellular luciferase expression) and the extent of AISE, which was further enhanced by the fraction of unsaturated helper lipid. Our findings reveal molecular and nanoscale changes occurring during AISE that underpin the LNPs' formulation-nanostructure-function relationship, aiding the rational design of application-directed gene delivery vehicles.

By mixing ionic liquids (ILs), it is possible to fine-tune their bulk and interfacial structure. This alters their physical properties and solvation behavior and is a simple way to prepare a collection of ILs whose properties can be tuned to optimize a specific application. In this study, mixtures of perfluorinated and alkylated ILs have been prepared, and links between composition, properties, and nanostructure have been investigated. These different classes of ILs vary substantially in the flexibility and polarizability of their chains. Thus, a range of useful structural and physical property variations are accessible through mixing that will expand the library of IL mixtures available in an area that to this point has received relatively little attention. In the experiments presented herein, the physical properties and bulk structure of mixtures of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide [C8MIM][Tf2N] and 1-(1H,1H,2H,2H-perfluorooctyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C8MIM-F13][Tf2N] have been prepared. The bulk liquid structure was investigated using a combination of small-angle X-ray and neutron scattering (SAXS and SANS, respectively) experiments in combination with atomistic molecular dynamics simulations and the measurement of density and viscosity. We observed that the addition of [C8MIM-F13][Tf2N] to [C8MIM][Tf2N] causes changes in the nanostructure of the IL mixtures that are dependent on composition so that variation in the characteristic short-range correlations is observed as a function of composition. Thus, while the length scales associated with the apolar regions (polar non-polar peak─PNPP) increase with the proportion of [C8MIM-F13][Tf2N] in the mixtures, perhaps surprisingly given the greater volume of the fluorocarbon chains, the length scale of the charge-ordering peak decreases. Interestingly, consideration of the contact peak shows that its origins are both in the direct anion···cation contact length scale and the nature (and hence volume) of the chains appended to the imidazolium cation.

Understanding the evolution process including foaming, stabilization and ageing of CO2 aqueous foams in high temperature, high-pressure (HTHP) environments is crucial for their rational use. However, most studies have been conducted through macroscopic observation, leading to inadequate insight into their intrinsic mechanisms. Herein we attempt to gain a comprehensive understanding of the evolution process by a combination of HTHP visualization foam meter, HTHP small-angle neutron scattering (SANS) and HTHP rheometry. A C-22-tailed tertiary amine, N-erucamidopropyl-N,N-dimethylamine (UC(22)AMPM), was first employed to develop robust CO2 foams. It was found the volume and lifetime of UC22AMPM-CO2 foams decrease by 24.7% and 56.9%, respectively, as the temperature rises from 25 C to 100 C at 8.5 MPa. The deterioration of the foam properties at elevated temperatures is attributed to the continuous phase viscosity reduced from 70 mPa.s to 25 mPa.s, leading to faster drainage, as well as to the coarsening rate increased from 6.60 x 10(4) to 9.83 x 10(5) mu m(3) min( 1), concomitant with the change in bubbles shapes, indicting enhanced coarsening and coalescence. Likewise, the decrease in pressure from 10 MPa to 1 MPa also resulted in a 46.7% and 91.0% reduction in foam volume and lifetime at 100 C, respectively. The impairment in foam properties with decreasing pressure also comes from the decrement of continuous phase viscosity, accelerating the drainage and thereby lowering the liquid fraction in the foam. The decreasing liquid fraction entails the liquid film to thin and weak, enhancing coarsening of bubbles and their merging. Our findings improve the insights into the foam evolution and pave a new road towards more comprehensive characterization of CO2 foam under HTHP conditions.

Hypothesis: As compared to common aliphatic surfactants, increasing the number of pendant or incorporated aromatic groups in a surfactant is expected to offer significant enhancement in the affinity for graphene surfaces. The basis for enhanced graphene-philicity of aromatic surfactants is that they can develop appreciable pi - pi interactions with graphene. Furthermore, charged (anionic) surfactants are expected to confer electrostatic stabilization on surfactant-graphene composites. Hence, it is expected that anionic aromatic surfactants combine these two properties for effective stabilization of graphene dispersions in water.& nbsp;Experimental: The properties of two custom made graphene-compatible surfactants carrying two and three aromatic moieties in the hydrophobic tails, namely DC3Ph2 (sodium 1,4-dioxo-1,4-bis(3-phenylpro poxy)butane-2-sulfonate) and TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3-phenylpro poxy)carbonyl) pentane-2-sulfonate) were compared with other common ionic commercial surfactants. Air-water (a/w) surface tension measurements were used to assess the surfactant adsorption and interfacial packing in the absence and presence of graphene. The surfactant coverage index for graphene (Phi) was calculated using surfactant headgroup areas derived from a/w surface tension data, chain volumes, and molecular fragment volumes from literature.& nbsp;Findings: Increasing the number of aromatic groups and tails per surfactant was shown to increase the ability of surfactants to pack and fill space, as expressed by Phi. Comparison between the values of Phi for surfactants of different chain structure and architecture showed that the affinity for graphene increased with Phi. Hence, there is an implicit link between surfactant-graphene compatibility and the identity, chemical composition and architecture of the surfactant chains. (C)& nbsp;& nbsp;2022 Elsevier Inc. All rights reserved.

Peptide self-assembly is a hierarchical process during which secondary structures formed in the initial stages play a critical role in determining the subsequent assembling processes and final structural ordering. Unusual secondary structures hold promise as a source to develop novel supramolecular architectures with unique properties. In this work, we report the design of a new peptide self-assembly strategy based on unusual α-sheet secondary structures. In light of the strong propensity of leucine toward forming helical conformations and its high hydrophobicity, we design two short amphiphilic peptides Ac-LDLLDLK-NH2 and Ac-DLLDLLDK-NH2 with alternating l- and d-form amino acids. Microscopic imaging, neutron scattering, and spectroscopic measurements indicate that the two heterochiral peptides form highly ordered wide nanotubes and helical ribbons with monolayer thickness, in sharp contrast to twisted nanofibrils formed by the homochiral peptide Ac-LLLLK-NH2. Molecular dynamics simulations from monomers to trimers reveal that the two heteropeptides fold into α-sheets instead of β-sheets, which readily pack into tubular architectures in oligomer simulations. Simulated circular dichroism spectra based on α-sheet oligomers validate the proposed α-sheet secondary structures. These results form an important basis for the rational design of higher-order peptide assemblies with novel properties based on unusual α-sheet secondary structures.

We report the synthesis of a new conjugated polymer bearing crown ether moieties, poly[(N(1-aza-[18]crown-6)carbamido)thiophene-2,5-diyl-alt-1,4-phenylene] (BG2). In water, BG2 forms a dispersion with a slightly cloudy appearance. We have studied the effect of adding surfactants, with different polar head groups, on these polymer-polymer aggregates. Special attention is given to the system with the anionic surfactant, sodium dodecyl sulfate (SDS). The combination of photophysical techniques with electrical conductivity, NMR (1H, 13C, and 27Na), DFT calculations, molecular dynamics simulations, and small-angle neutron scattering (SANS) provides a detailed picture on the behavior of the SDS/BG2 system in aqueous solution and in thin films. NMR, electric conductivity, and DFT results suggest that hydrophilic interactions occur between the polar headgroup of the surfactant (OSO3- Na+) and the aza-[18]-crown-6 moiety. DFT calculations confirmed the capability of BG2 to form stable complexes with the Na+ cations, where the cation can be either inside the azacrown cavity or sandwiched between the cavity and the polymer chain, which seem to determine the position of the surfactant hydrocarbon chain and, therefore, be responsible for the disruption of the BG2 aggregates and subsequent increase in the photoluminescence quantum yields. SANS measurements, made with hydrogenated and deuterated SDS in D2O, clearly show how micron-sized aggregates of BG2 are broken down by SDS and then how BG2 becomes preferentially incorporated within joint colloidal particles of BG2 and SDS with increasing [SDS]/[BG2] molar ratio.

The preparation of mixtures of ionic liquids (ILs) represents an attractive strategy to tune their properties, an important aspect of which is to understand how the structure of the bulk varies with composition. In this study, small-angle neutron scattering (SANS) was used to probe mixtures of methylimidazolium-based ionic liquids [Cnmim][Tf2N] with [C2mim][Tf2N]) (n = 4, 6, 8 and 10) and of [Cmmim][Tf2N] with [C12mim][Tf2N] (m = 2, 4, 6 and 8). Mixtures were prepared in both contrasts, which is to say that one component would be fully hydrogenated while the other was fully deuterated, and vice versa. Data were fitted using a range of appropriate models, of which the Teubner-Strey model provided most useful information and the pure materials showed a nascent Polar Non-polar Peak (PNPP) for n = 6, which became more evident as n increased. In the mixtures [Cnmim]x[C2mim]1-x[Tf2N], the PNPP was evident for n = 10 and 8, nascent for n = 6 and absent for n = 4, with percolation showing a very strong dependence on the chain length of the added IL, [Cnmim][Tf2N]. In contrast, while the ability of [C12mim][Tf2N] to form percolated structures was damped when mixed with [Cmmim][Tf2N], as m increased from 2 to 6, this effect was less strong. However, data obtained for mixtures of [C12mim][Tf2N] and [C8mim][Tf2N], both of which percolate as pure materials, did not fit easily in any of the models applied to the previous systems and gave results that depended on the contrast used. Complementary small-angle X-ray scattering (SAXS) data, however, showed the expected evolution and behaviour of the PNPP, COP and CP, revealing that the unexpected observations were due to an adventitious matching out of isotopic contrasts. As well as revealing details of the structures of these IL mixtures, the results also point to complementary strategies for generating bulk percolated structures as a function of cation chain length.