Tape-like Structures Research Articles

Multiscale Characterisation of Staple Carbon Fibre-Reinforced Polymers

The aim of this study was to characterise the microstructural organisation of staple carbon fibre-reinforced polymer composites and to investigate their mechanical properties. Conventionally, fibre-reinforced materials are manufactured using continuous fibres. However, discontinuous fibres are crucial for developing sustainable structural second-life applications. Specifically, aligning staple fibres into yarn or tape-like structures enables similar usage to continuous fibre-based products. Understanding the effects of fibre orientation, fibre length, and compaction on mechanical performance can facilitate the fibres’ use as standard engineering materials. This study employed methods ranging from microscale to macroscale, such as image analysis, X-ray computed tomography, and mechanical testing, to quantify the microstructural organisations resulting from different alignment processing methods. These results were compared with the results of mechanical tests to validate and comprehend the relationship between fibre alignment and strength. The results show a significant influence of alignment on fibre orientation distribution, fibre volume fraction, tortuosity, and mechanical properties. Furthermore, different characteristics of the staple fibre tapes were identified and attributed to kinematic effects during movement of the sliver alignment unit, resulting in varying tape thicknesses and fuzzy surfaces.

Fluorescence microscope observation of the structure of a calcium alginate hydrogel

Abstract Calcium alginate hydrogels are used in a wide range of applications in the food, medical, pharmaceutical, and cosmetic industries. I have studied a calcium alginate hydrogel as an ultrasound phantom material. This hydrogel is formed using sodium alginate, calcium sulfate dihydrate, trisodium phosphate 12-hydrate, glycerol, and water, and mimics the ultrasound properties of human soft tissue. In this study, the structure of the calcium alginate hydrogel was observed with a fluorescence microscope after staining with the calcium indicator calcein. Two types of hydrogel structures, tape-like and thread-like, were observed by this method. The thread-like structures were rare in the hydrogel, which made them more difficult to find than the tape-like structures. These structures were several micrometers in diameter and longer than the tape-like structures, which were several micrometers to several tens of micrometers wide. The thread-like structures spread out in three dimensions, and existed singly or in aggregates. The outer shape of the aggregated thread-like structures resembled the shape of the tape-like structures, which suggested that the tape-like structures were made up of thread-like structures. The tape-like and thread-like structures are thought to contribute to retention of water, which is the main component of a hydrogel, by surrounding it.

The coordination chemistry of benzhydrazide with lanthanide(iii) ions: hydrothermal in situ ligand formation, structures, magnetic and photoluminescence sensing properties.

The influence of synthetic conditions on the solid-state structural formation of lanthanide(iii) complexes based on a hydrazide ligand have been investigated and reported. Depending on the solvents and reaction temperatures, the reactions of hydrated Ln(NO3)3 with a benzohydrazide (bzz) ligand afforded three classes of lanthanide(iii) coordination complexes viz. [Ln(bzz)(NO3)](NO3)2 (1Ln; Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), [Ln(bzz)(ben)3(H2O)]·H2O (2Ln; Ln = Pr (6), Nd (7), Sm (8), Eu (9), Gd (10), Tb (11), Dy (12), Er (13)), and [Ln3(ben)3] (3Ln; Ln = Eu (14), Gd (15), Tb (16), Dy (17), Er (18), Tm (19), Yb (20), Lu (21)). Complexes 1–5 in series 1Ln were isolated by slow evaporation of their isopropanol solutions at ambient temperature, and the complexes display similar discrete structures bearing distinct intermolecular N–H⋯O hydrogen bonds to generate a three-dimensional (3D) supramolecular architecture. Complexes 6–13 in series 2Ln were obtained under hydrothermal conditions at 110 °C where the in situ generated benzoate (ben) ligands participated in the formation of one-dimensional (1D) coordination polymers (CPs) with the bzz ligands. At a temperature of 145 °C the hydrothermal conditions result in the formation of the thermodynamically more stable products of 14–21 in series 3Ln, in which the bzz ligand underwent complete in situ hydrolysis to create the ben ligand. These coordination assemblies feature 1D zigzag chains that are formed by unusual low coordination numbers of the six- and seven-fold coordinated Ln3+ centers bridged by the ben ligands in μ2- and μ3-coordination modes. Notably, the chain structures of 2Ln can be transformed into the zigzag tape-like structures of 3Ln upon heating the crystalline samples to 400 °C in air. In the solid state at room temperature, the Eu- (2, 9, 14) and Tb- (4, 11, 16) containing complexes emit red and green light, respectively. The luminescence investigations show that the Eu- (9, 14) and Tb-(11, 16) based CPs could be used as fluorescent probes for acetone and Co2+ ions via an energy competition mechanism. Meanwhile, the Gd- (10, 15) and Dy- (12, 17) based CPs show typical antiferromagnetic interactions.

Solvent Molding of Organic Morphologies Made of Supramolecular Chiral Polymers

The self-assembly and self-organization behavior of uracil-conjugated enantiopure (R)- or (S)-1,1'-binaphthyl-2,2'-diol (BINOL) and a hydrophobic oligo(p-phenylene ethynylene) (OPE) chromophore exposing 2,6-di(acetylamino)pyridine termini are reported. Systematic spectroscopic (UV-vis, CD, fluorescence, NMR, and SAXS) and microscopic studies (TEM and AFM) showed that BINOL and OPE compounds undergo triple H-bonding recognition, generating different organic nanostructures in solution. Depending on the solvophobic properties of the liquid media (toluene, CHCl3, CHCl3/CHX, and CHX/THF), spherical, rod-like, fibrous, and helical morphologies were obtained, with the latter being the only nanostructures expressing chirality at the microscopic level. SAXS analysis combined with molecular modeling simulations showed that the helical superstructures are composed of dimeric double-cable tape-like structures that, in turn, are supercoiled at the microscale. This behavior is interpreted as a consequence of an interplay among the degree of association of the H-bonded recognition, the vapor pressure of the solvent, and the solvophobic/solvophilic character of the supramolecular adducts in the different solutions under static and dynamic conditions, namely solvent evaporation conditions at room temperature.

Alkaline earth metal (Mg, Sr, Ba)-organic frameworks based on 2,2',6,6'-tetracarboxybiphenyl for proton conduction.

Three new alkaline earth metal based metal-organic frameworks (MOFs), namely M-BPTC (M = Mg, Sr, Ba), have been synthesized by using BPTC (2,2',6,6'-tetracarboxybiphenyl) as ligand under hydrothermal conditions. These MOFs exhibit interesting structural diversity, variable chemical and thermal stability, as well as proton conductivity. Mg-BPTC with the formula {[Mg(BPTC)0.5(H2O)3]·5H2O}n consists of BPTC(4-) extended metal layers, and novel highly ordered infinite tape-like structures of cyclic water octamers reside interlayer. Three-dimensional porous {[Sr2(BPTC)(H2O)6]·H2O}n (Sr-BPTC) features inorganic Sr-O chains (I(1)O(2)) and open hydrophilic channels where water heptamers and carboxyl oxygen atoms conspire to form H-bond networks, whereas 3D {[Ba6(BPTC)3(H2O)6]·11H2O}n (Ba-BPTC) shows Ba-O inorganic layer (I(2)O(1)) and 1D channels incorporating large water 14-mers and 18-mers. M-BPTC (M = Mg, Sr) species exhibit excellent water stability and proton conductivity due to their respective appropriate pathways for proton transporting. M-BPTC (M = Sr, Ba) structures are highly thermally stable due to the presence of the inorganic connectivity. The present results suggest that M-BPTC (M = Mg, Sr) are promising materials for proton conduction and provide insight into the hydrogen bonding motif.

Application of solubility parameters in a D-sorbitol-based organogel in binary organic mixtures.

The gelation behaviour of a low molecular weight gelator 2,4-(3,4-dichlorobenzylidene)-D-sorbitol (DCBS) in a binary solvent system has been studied. DCBS was soluble in pure ethanol and insoluble in pure methylcyclohexane. However, DCBS formed opaque gels in ethanol-methylcyclohexane mixtures when the methylcyclohexane content varied from 50% to 80%. Within this range, an increase in the amount of methylcyclohexane reduced the gelation time and also caused the minimum gelation concentration to decrease. Scanning electron microscopy showed that the three-dimensional network structures of the xerogels became denser (from tape-like structures to uniform fibres) when the methylcyclohexane content increased from 40% to 80%. The precipitates that formed in 90% and 100% methylcyclohexane had rod-like structures. X-ray diffraction of the xerogels showed that in the gel state, the DCBS gelator had lamellar packing, which was different from the structure of the precipitate. Fourier transform infrared spectroscopy of the xerogels showed that H-bonding was a driving force for the self-aggregation of the DCBS and it was enhanced as the methylcyclohexane content increased. To estimate the gelator-solvent interactions, the Flory-Huggins parameter was calculated for the DCBS gelator in the binary mixed solvent systems. Based on the values of the Flory-Huggins parameter, the gelation behaviours could be grouped into four domains (solution, partial gel, gel and precipitation). This is a simple method to predict the gelation behaviour of DCBS in some mixed solvents.

The effect of pH on the self-assembly of a collagen derived peptide amphiphile

Transitions in nanostructure driven by pH are observed for a self-assembling peptide amphiphile (PA) with a cationic pentapeptide headgroup. At pH 3, the PA forms flat tape-like structures, while at pH 4 the PA assembles into twisted right handed structures. These twisted structures transform again to flat tape-like structures at pH 7. In complete contrast, spherical micelles are observed at pH 2. These changes in response to pH may be relevant to biological and pharmaceutical applications of this PA in skincare.

Hydrogen-bond-assisted supramolecular 1-D tape-like structures of mesogenic bis-pyrazoles

Two new series of isomeric bis-pyrazoles 1a–b are prepared, characterized, and their mesomorphic properties investigated. These pyrazoyl derivatives were obtained from the condensation of α,β-diketones 2a–b with hydrazine monohydrate in refluxing THF. Two single crystallographic structures of compounds mesogenic 1a (n=14) and nonmesogenic 1b (n=8) were determined by X-ray analysis. Both 1a–14 and 1b–8 crystallize in a triclinic space group P−1 and monoclinic C2/c group, respectively. An extended H-bonded structure was formed in both crystal lattices, giving a pseudo 1D-polymeric tape-like structure. Derivatives 1a exhibited smectic A/C mesophases, in contrast, derivatives 1b were all nonmesogenic. The difference in mesomorphic behavior was attributed to the between linear conformation and the coplanarity of the five rings over than in 1a. The correlation between the molecular structures and the mesomorphic properties is discussed.

RETRACTED: Soft Nanotubes Acting as a Light-Harvesting Antenna System

Amphiphilic monomers, which were quantitatively synthesized from a dehydration reaction between a glycolipid and naphthalene-boronic acids, self-assembled in organic solvents to selectively form tape-like structures (nanotape) and tubular structures (nanotube) depending on the bond position of the boron atom in the naphthalene ring. The nanotube has a strong narrow fluorescence band attributable to the monomer species of the naphthalene group, whereas the nanotape has a weak broad fluorescence band at a relative longer wavelength region based on the excimer species of the naphthalene group. Light energy adsorbed by the naphthalene groups densely and regularly organized in the bilayer membrane wall of the nanotube was transferred, with high quantum efficiency, into anthracene as an acceptor encapsulated in the nanochannel. The supramolecular nanotube proved to be able to act as a light-harvesting antenna.

Overlapping Double Turn Conformations Adopted by Tetrapeptides Containing Non-Coded α-Amino Isobutyric Acid (AIB) and Formation of Tape-Like Structures Through Supramolecular Helix Mediated Self-Assembly

Single crystal X-ray diffraction studies and solvent dependent (1)H NMR titrations reveal that a set of four tetrapeptides with general formula Boc-Xx(1)-Aib(2)-Yy(3)-Zz(4)-OMe, where Xx, Yy and Zz are coded L-amino acids, adopt equivalent conformations that can be described as overlapping double turn conformations stabilized by two 4-->1 intramolecular hydrogen bonds between Yy(3)-NH and Boc C=O and Zz(4)-NH and Xx(1)C=O. In the crystalline state, the double turn structures are packed in head-to-tail fashion through intermolecular hydrogen bonds to create supramolecular helical structures. Field emission scanning electron microscopic (FE-SEM) images of the tetrapeptides in the solid state reveal that they can form flat tape-like structures. The results establish that synthetic Aib containing supramolecular helices can form highly ordered self-aggregated amyloid plaque like human amylin.

Switch-Peptides to Trigger the Peptide Guided Assembly of Poly(ethylene oxide)−Peptide Conjugates into Tape Structures

A strong beta-sheet forming peptide was conjugated to PEO and utilized to guide the structure formation process toward well-defined, tape-like structures with millimeters in length, about 2 mum width, and approximately 50 nm height. The aggregation tendency of the peptide was temporarily suppressed for ease of synthesis by the integration of multiple switch-peptide defect segments into the peptide backbone. A subsequent rearrangement in the defects re-establishes the native peptide backbone and triggers the assembly by switching the aggregation properties on.

Substituent Effects Control the Self-Association of Molecular Clips in the Crystalline State

We report the X-ray crystal structure of 11 molecular clips and analyze the influence of substituents (e.g., OMe, Me, and NO2) and their location on the observed crystal packing. Molecular clips 3a and 3b form tapelike structures in the crystal due to pi-pi interactions between the aromatic walls. Compounds 3d, 3eC, and 3fC form dimers driven by critical C-H...O interactions and then form tapes driven by pi-pi interactions in the crystal. These two building motifs, pi-pi and C-H...O interactions, can be used to rationalize the enantio- and diastereoselectivity observed in the X-ray crystal structures of the remaining five molecular clips. For example, the C-H...O interactions are found to dictate the formation of homochiral dimers in the structures of (+/-)-3eT and (+/-)-3fT and to control the diastereoselective formation of 6a2-6c2 dimeric motifs with internal p-dimethoxy-o-xylylene walls. Overall, the results suggest that substituent effects that induce even weak intermolecular interactions (e.g., C-H...O) can be used to reliably control crystal packing within glycoluril-based systems.

Glycoluril diamide dihydrate

The crystal structure of the title compound, cis-N,N′-bis(2-hydroxy­ethyl)-4,8-dioxo-2,6-dioxa-3a,4a,7a,8a-tetra­aza­cyclo­penta­[def]­fluorene-8b,8c-dicarbox­amide dihydrate, C14H20N6O8·2H2O, is reported. The compound forms tape-like structures comprising 14- and 10-membered hydrogen-bonded rings. These hydrogen-bonded tapes form hydrogen-bonded sheets and stacks of sheets by hydrogen-bonding interactions with the solvent water mol­ecules.

Maxillae and mandibles of male mosquitoes and female autogenous mosquitoes (Diptera: Culicidae).

Maxillae and mandibles of males of 44 species of 12 mosquito genera and females of three autogenous genera and two partially autogenous species were examined under light microscopy and scanning electron microscopy. The maxillae and mandibles of male mosquitoes are delicate, tape-like structures with lengths characterizing genera or higher level classification units. Five patterns are recognized: (A) long maxillae and mandibles with mandibles longer than maxillae in Anopheles; (B) long maxillae and mandibles with maxillae longer than mandibles in Toxorhynchites; (C) short or intermediate lengths of maxillae with short mandibles in Aedes, Armigeres, Culex, Ochlerotatus, Orthopodomyia, and Uranotaenia; (D) short or intermediate length of maxillae with no mandibles in Mimomyia and Tripteroides; and (E) no maxillae and mandibles in Malaya and Topomyia. Maxillary and mandibular lengths of male mosquitoes show a positive correlation. Length of maxillae and mandibles of autogenous females are reduced to the same level as conspecific males. In contrast, females of partially autogenous species have complete maxillae and mandibles as in females of anautogenous species.

Thermodynamic stabilities of linear and crinkled tapes and cyclic rosettes in melamine--cyanurate assemblies: a model description.

In this paper we describe model calculations for the self-assembly of N,N-disubstituted melamines 1 and N-substituted cyanuric acid or 5,5-disubstituted barbituric acid derivatives 2 into linear or crinkled tapes and cyclic rosettes via cooperative hydrogen bond formation. The model description considers all possible stereoisomeric tape structures consisting of two to eight different components (270 different species in total) and one cyclic hexameric rosette structure. Furthermore, eight steric parameters (R(12)-R(28)) are included that represent the different types of steric interactions within the assemblies. Most importantly, the model calculations clearly show that the tape/rosette ratio is very sensitive to changes in parameters that directly affect the internal energy of the rosette structure. In this respect, three parameters have been characterized, i.e., the basic equilibrium constant K(0) for the bimolecular association of a melamine and cyanurate, the equilibrium constant K(r)/K(0) for the cyclization of a linear hexamer, and the parameter R(12)-a(Z)b, representing attractive or repulsive interactions between adjacent melamine and cyanurate moieties. For example, an increase in K(0) from 100 to 10,000 M(-1) ([A](0) = [B](0) = 10 mM, K(r) = 0.01 M) or in K(r) from 0.001 to 0.1 M ([A](0) = [B](0) = 10 mM, K(0) = 1000 M(-1)) raises the concentration of the rosette from <5 to approximately 90% or from approximately 10 to approximately 85%, respectively. Similarly, a change in R(12)-a(Z)b from 1.0 (no repulsive or attractive interactions) to 1.5 (slight attractive interaction) raises the rosette fraction of the mixture from 25% to 45%. In sharp contrast to this, the model calculations show that parameters that only affect the internal energy of the tapes (R(13)--R(28)) hardly change the tape/rosette ratio. For example, by changing R(13)-a(EE)a from 1.0 (no repulsive or attractive interactions) to 0.001 (maximum repulsion), the rosette fraction in the mixture changes by no more than 8%. Including all possible sterics that occur only in tapes (i.e., R(13)--R(28)), the maximum change in rosette fraction is no more than 16%. These predictions can be rationalized by considering that any change in the stability of the tapes only affects the rosette concentration by means of shifting the equilibrium between free 1 and 2 and the rosette. Since there are 270 different tapelike structures in equilibrium, this mixture represents the best buffer solution in the world. These model calculations seem to conflict with the concept of peripheral crowding as put forward by Whitesides et al., which states that bulky substituents on the periphery of the melamine (and cyanurate) components can be used to shift the tape/rosette equilibrium completely toward the rosette structure. Computer simulations (CHARMm 24.0) show that linear tapes with bulky substituents are severely distorted from planarity, while the corresponding rosette remains planar. Therefore, tapelike structures with bulky substituents are expected to have a much higher solubility than the corresponding rosettes, which can explain the observed crystal data.

A study of supramolecular hydrogen bonded complexes formed by aliphatic dicarboxylic acids with azaaromatic donors

Crystal structures of the hydrogen bonded, 1:1 molecular complexes of malonic, glutaric, adipic, thiodiglycolic and thiodipropionic acids with 4,4′-bipyridyl have been investigated in detail. All the dicarboxylic acids form molecular tape-like structures, but thiodiglycolic acid gives a cyclic structure, favoured by intermolecular π- π interaction between the heteroatom-rings. The cyclic structure is indeed unique, in the sense that it represents a noncovalent synthesis of a rectangle. Crystal structures of hydrogen bonded molecular complexes of malonic, succinic, glutaric, adipic and thiodipropionic acids with 2,4,6-triaminopyrimidine have been studied. By and large, only tape-like structures are formed, the crossed ribbon network being favoured in the complexes of malonic and glutaric acids with an odd number carbon atoms. In all the complexes of 2,4,6-triaminopyrimidine, proton transfer occurs from the carboxyl group to the heteroatom nitrogen, giving rise to a strong hydrogen bonded cyclic system.

Assembly and local structure of MoS2 colloidal platelets on quartz and muscovite Mica surfaces

Aqueous suspensions of MoS2 colloidal platelets and their assembly after casting on quartz and cleaved muscovite mica (001) surfaces have been investigated by optical spectroscopy and atomic force microscopy (AFM). Optical spectra are consistent with the presence of non-metallic distorted pseudo-octahedral (MoS2)n-based moieties. Features observed between 800–1300 nm in single layers, at low platelet stacking order and when traces of Li+ remain (but not in either 2H-MoS2 or 1T-MoS2) are assigned to transitions from a split dx2,yz,xzOh MoS2 band to other d levels in a complex (rather than band) formulation. Differences in optical spectra of platelets on (001) mica and on quartz, both as-cast and after annealing at > 120 °C (when the films undergo a phase transition) are ascribed to differences in platelet assembly involving water bilayers (H2O vibrational combination bands are observed in mica but not in quartz). AFM micro-imaging shows MoS2 colloidal platelets assemble randomly, including as almost vertical packets (as on γ-alumina) on quartz over a wide concentration range. Instead, on mica (001) surfaces the cast assembly orders as a network of laterally developed tapelike structures (albeit with stacking faults). Single tapes are 200–300 nm wide, ca. 4 nm high and > 3 µm long and probably arise via side-on platelet fixture involving a complex platelet parking mechanism. It is suggested that horizontal dispersion and re-stacking of the platelets is directed by the charged mica surface. After annealing at 200 °C, MoS2 platelets on mica give single layers of minimum thickness 6.2 ± 0.2 A, having a0= 3.2 A(by AFM) as expected for a 2H-MoS2 structure. [MoS2 films prepared by reaction of MoO3 or MoCl5+ H2S via hard methods (CVD, sputtering, etc.) give vertically-oriented MoS2 platelets.] Colloidal MoS2 cast on GaAs(111) and Si(111) surfaces gives rise to a micro-crystalline environment via platelet scission and surface reactions. At the limit, annealing MoS2 plates on both surfaces at 200 °C leads to complete disappearance of MoS2 islands due to reaction of S2– with the surface.