Side Chain Length Research Articles

Synthesis of aglycones, structure-activity relationships, and mode of action of lycosides as inhibitors of the asexual reproduction of Phytophthora.

Phytophthora are plant pathogens that damage agricultural products. Lycosides (1a-d), found in vegetable juice, have the potential to curb the rapid outbreak and crop damage caused by the asexual reproduction of Phytophthora. Here, aglycones 2a, b with slightly higher activity than lycosides were synthesized as a diastereomeric mixture (mix-2) possessing activity (IC50=4.1 µm) comparable with that of lycosides. The importance of the cyclohexanone structure and side-chain length was demonstrated via structure-activity relationship analysis using synthetic intermediates. In addition, the action mechanism of lycosides was investigated using transcriptome analysis, which revealed a contribution to proline biosynthesis inhibition, a process crucial for the asexual reproduction of Phytophthora. These findings indicate that lycosides (and aglycone) are environmentally benign agents that can be used for protecting agricultural products from Phytophthora pathogens.

On the Binding Mechanisms of Calcium Ions to Polycarboxylates: Effects of Molecular Weight, Side Chain, and Backbone Chemistry.

We experimentally determined the characteristics and Langmuir parameters of the binding of calcium ions to different polycarboxylates. By using potentiometric titrations and isothermal titration calorimetry, the effects of side chain chemistry, pH value, and chain length were systematically investigated using the linear polymers poly(aspartic acid), poly(glutamic acid), and poly(acrylic acid). We demonstrate that for polymers with high polymerization degrees, the binding process is governed by higher-order effects, such as the change of apparent pKa of carboxyl groups, and contributions arising from the whole polymer chain while the chemistry of the monomer unit constituting the polymer plays a subordinate role. In addition, primary binding sites need to be present in the polymer, thus rendering the abundance and sequential arrangement of protonated and deprotonated groups important. The detection of higher-order effects contradicts the assumptions posed by the Langmuir model of noninteracting binding sites and puts a question mark on whether ion binding to polycarboxylates can be described using solely a Langmuir binding model. No single uniform mechanism fits all investigated systems, and the whole polymer chain, including terminal groups, needs to be considered for the interpretation of binding data. Therefore, one needs to be careful when explaining ion binding to polymers solely based on studies on monomers or oligomers.

Analyzing the Mechanical Properties of Free-Standing PACA Thin Films Using Microindentation Technique.

Assessing the mechanical properties of materials is of fundamental relevance for their rational usage, but can be challenging with standard tensile testing for highly brittle polymers used, e.g., as coatings. Here, a procedure for the mechanical analysis of free-standing poly(alkyl cyanoacrylate) (PACA) films using microindentation has been explored. Rigid and transparent films from PACA with various side chain compositions were formed on top of square polymer frames by in situ polymerization. Under microscopic control, the free-standing films were analyzed using a microelectromechanical sensing system. By this procedure, decreasing Young's moduli E for increasing PACA side chain length and flexibility were determined with strain at break εB between 0.36% for poly(ethyl cyanoacrylate) and 4.6% for poly(methoxyethyl cyanoacrylate). Based on this successful application, the applied methodology may be relevant for characterizing various coating materials, which are otherwise hard to form as thin free-standing films, and using the data, e.g., in computationally assisted design and evaluation of hybrid material devices.

Succinate‐based plasticizers: Effect of plasticizer structure on the mechanical and thermal performance of poly(vinyl chloride) plastic formulations

AbstractA new family of succinate‐based plasticizers, consisting of molecules with a linear alkyl chain capped with n‐alkyl succinates on both ends, was evaluated as potential bio‐based plasticizers for stiff polymers. The influence of the central and side alkyl chain lengths on the mechanical and thermal properties as well as the migration behavior of poly(vinyl chloride) (PVC)/plasticizer blends was evaluated. The central chain length had the greatest influence on plasticizer performance, with shorter chains leading to blends with higher stress at break and surface hardness, whereas long chains produced softer blends. An optimum chain central length of five carbon atoms was observed, with longer chains leading to reduced compatibility and exudation of the plasticizer at higher plasticizer concentrations. The entire family of plasticizers performed comparably or better than the commercial plasticizer di(2‐ethylhexyl) phthalate (DEHP) when incorporated into the blend at concentrations of 20–60 parts per hundred resin (phr). Overall, the succinate‐based plasticizers/PVC blends all exhibited equal or improved tensile properties (by up to 77%), surface hardness (reduced by up to 43%), glass transition temperature (reduced by up to 11°C), and migration into organic media (reduced by up to 38%) when compared with blends with DEHP at 40 phr.

Understanding the Molecular Features Controlling the Solubility Differences of R-134a, R-1234ze(E), and R-1234yf in 1-Alkyl-3-methylimidazolium Tricyanomethanide Ionic Liquids

This work reports a study of the absorption of fluorinated refrigerant gases in ionic liquids (ILs) from a combined experimental and computational approach to gain insights into the solvation of these greenhouse gases. The results allow the selection of solvents for fluorinated gas recovery, based on molecular characteristics, and improve the recyclability of these high-value-added compounds. The solubility of R-134a, R-1234yf, and R-1234ze(E) was measured experimentally in 1-alkyl-3-methylimidazolium tricyanomethanide ILs at 283.15–323.15 K and up to 5 bar to investigate the influence of the alkyl side chain length of the cations in the ILs. Molecular dynamics was used to study solvation environments around refrigerant molecules in terms of radial distribution functions, coordination numbers, and spatial distribution functions. Simulations were carried out with the recent CL&Pol polarizable force field for ILs, which includes polarization effects explicitly. The force field was validated against experimental solubility through free-energy perturbation calculations. The main effects influencing the solubility of fluorinated refrigerants in ILs result from interactions with the anions and with the cation head group alkyl chain, setting a basis for a rational selection and design of ILs for processes to recover and recycle refrigerants in a circular economy model.

Geochemical distortion on shale oil maturity caused by oil migration: Insights from the non-hydrocarbons revealed by FT-ICR MS

Oil migration may influence the reliability of molecular maturity parameters. Sample extracts from a shaly sequence subjected to intrasource migration, were characterized using FT-ICR MS and GC–MS techniques. The hydrocarbon maturity parameters including sterane isomer ratios and methylphenanthrene indices (MPI) are relatively higher in siltstones than in shales. In contrast, the non-hydrocarbons indicate a lower maturity in siltstones as revealed by the smaller size of molecular cores, the larger length of alkyl side chains, and the more enrichment of Ox species. It is concluded that this discrepancy is attributable to petroleum migration. The thermal-stable isomers of hydrocarbons, used as numerators in the ratios, have stronger mobility consequently leading to a faster migration into siltstones. In contrast, the molecules of non-hydrocarbons with low aromatization and molecular size, and higher alkylation degrees, easily migrate into the siltstones due to relatively lower polarity, precipitability, and absorptivity. Additionally, the hydrophilic matrix surface and high porosity of the strata also facilitate the accumulation of non-hydrocarbons in the siltstones during the early diagenesis. Such findings contribute to a better understanding of oil molecular migration behavior, and suggest a caution for using geochemical indices as maturity parameters when involving petroleum migration.

Intrachain and interchain complexation of polyacrylic acids bottlebrush chains with Ca2+ in aqueous solutions

In this work, by combing static light scattering (SLS), dynamic light scattering (DLS) and atomic force microscopy (AFM), we have explored how the topological effect influences the intrachain and interchain complexation of polyelectrolytes and divalent ions. First, by a combination of atom transfer radical polymerization (ATRP) and click reaction, two polyacrylic acid (PAA) bottlebrush samples, i.e. PPA 1210 - g -PAA 20 and PPA 2570 - g -PAA 20 , with nearly identical graft density and PAA sidechain length but different backbone lengths, have been prepared. Second, for comparison, a linear sample l -PAA 7710 , with a similar chain size compared to PPA 1210 - g -PAA 20 , has been also prepared. Third, we have systematically investigated the intrachain and interchain complexation between NaPAA topological chains and divalent calcium ions. It is revealed that the intrachain interaction for linear l -PPA 7710 is much stronger than that for bottlebrush samples due to the flexibility feature, while the interchain interaction displays the opposite trend. It is also found that the addition of Ca 2+ results in the change of conformation from loose random coils to dense sphere for l -PAA 7710 , while the overall conformations of PPA 1210 - g -PAA 20 and PPA 2570 - g -PAA 20 almost remain unchange, which can be ascribed to the unique branched structure and enhanced structural rigidity. • Two bottlebrush samples with nearly identical graft density, sidechain length but different backbone lengths were prepared. • The intrachain and interchain complexation between NaPAA topological chains and Ca 2+ were systematically investigated. • The addition of Ca 2+ results in the change of conformation for linear sample while the bottlebrush samples remain unchanged.

The effect of extended alkyl length on molecular orientation of nonfullerene acceptor: A case study in as-cast polymer solar cells

In this work, the effective electronic coupling on the indacenodithiophene (IDT)-based nonfullerene core was investigated by changing the length of the linear alkyl side chain. Extended linear alkyl side chain reduces the extinction coefficient in thin films and promotes the tendency of nonfullerene molecules to edge-on orientation. The theoretical calculation illustrates that the enhanced electronic coupling stem from short alkyl side chain could be beneficial for face-on orientation and charge transport. For the as-cast solar cells, the devices based on IDIC with the short alkyl side chain possessed the best efficiency. Our result manifests that the linear alkyl chain on the core of nonfullerene acceptor dominates molecular packing mode, light absorption, bulk heterojunction size, charge carrier transport and recombination dynamics.

Influence of the Alkyl Side Chain Length on the Assembly and Thermochromic Solid-State Properties in Symmetric and Asymmetric Monoalkoxynaphthalene–Naphthalimide Donor–Acceptor Dyads

We have been investigating monoalkoxynaphthalene–naphthalimide (MAN–NI) donor–acceptor dyads that undergo a unique and dramatic orange-to-yellow thermochromic transition in the solid state. This study reports a new series of these stimuli-responsive solids, based on dyads with symmetric and relatively long alkyl side chains, as well as asymmetric derivatives. The length of the alkyl side chains influenced the structures, properties, and dynamic behavior of the resulting solids. All of the symmetric alkyl side chain derivatives can crystallize with identical packing (allowing for alkyl chain length differences) in a lasagna-like fashion with alternating alkyl and stacked aromatic layers. The fully extended alkyl side chains are aligned in an interdigitated, “cork and bottle” fashion. The aromatic layers feature head-to-head stacking geometries of the aromatic dyad cores. The crystalline solids derived from each of these derivatives undergo dramatic thermochromic orange-to-yellow transition in the solid state. Crystal structures were obtained for three of the four asymmetric dyad derivatives. In each case, layered structures were observed, although the mismatch in alkyl side chain lengths results in a unique hybrid alkyl/aromatic layer. Two of the asymmetric derivatives exhibit almost identical head-to-head dyad core stacking geometries, while one exhibits a head-to-tail dyad core stacking geometry. Of the four asymmetric dyads studied, only two asymmetric derivatives with the longer alkyl side chains exhibit dynamic solid-state behavior. Overall, our results demonstrate the relatively general nature of the thermochromic orange-to-yellow color-changing mechanism of the MAN–NI dyads and verify the link between the alkyl side chain interactions and this interesting stimuli-responsive behavior in the solid-state.

Targeting Parallel Topology of G-Quadruplex Structures by Indole- Fused Quindoline Scaffolds.

Preferential stabilization of G-quadruplex (G4) structures using small-molecule ligands has emerged as an effective approach to develop anticancer drugs. Herein, we report the synthesis of three indole-fused quindoline derivatives with varying lengths of side chains (InqEt1, InqEt2, and InqPr2) as selective ligands for promoter G4 structures. The ligands stabilize the parallel topology of c-MYC and c-KIT1 promoter G4 DNAs over telomeric and duplex DNAs, as evident from the circular dichroism melting and polymerase stop-assay experiments. The lead ligand, InqPr2, downregulates the gene expression of c-MYC and c-KIT in HeLa and HepG2 cells, respectively, leading to apoptotic cell death. Molecular modeling and dynamics studies support the 2:1 binding stoichiometry revealed from the Job plot analysis and show the ligand's structural features that enable the preferential binding to the parallel G4 structures over other topologies. Our studies show that indole-fused quindoline derivatives can be harnessed as new molecular scaffolds for selective targeting of parallel G4 topologies.

Side‐Chain Control of Topochemical Polymer Single Crystals with Tunable Elastic Modulus

AbstractTopochemical polymerizations hold the promise of producing high molecular weight and stereoregular single crystalline polymers by first aligning monomers before polymerization. However, monomer modifications often alter the crystal packing and result in non‐reactive polymorphs. Here, we report a systematic study on the side chain functionalization of the bis(indandione) derivative system that can be polymerized under visible light. Precisely engineered side chains help organize the monomer crystals in a one‐dimensional fashion to maintain the topochemical reactivity. By optimizing the side chain length and end group of monomers, the elastic modulus of the resulting polymer single crystals can also be greatly enhanced. Lastly, using ultrasonication, insoluble polymer single crystals can be processed into free‐standing and robust polymer thin films. This work provides new insights on the molecular design of topochemical reactions and paves the way for future applications of this fascinating family of materials.

Side-Chain Control of Topochemical Polymer Single Crystals with Tunable Elastic Modulus.

Topochemical polymerizations hold the promise of producing high molecular weight and stereoregular single crystalline polymers by first aligning monomers before polymerization. However, monomer modifications often alter the crystal packing and result in non-reactive polymorphs. Here, we report a systematic study on the side chain functionalization of the bis(indandione) derivative system that can be polymerized under visible light. Precisely engineered side chains help organize the monomer crystals in a one-dimensional fashion to maintain the topochemical reactivity. By optimizing the side chain length and end group of monomers, the elastic modulus of the resulting polymer single crystals can also be greatly enhanced. Lastly, using ultrasonication, insoluble polymer single crystals can be processed into free-standing and robust polymer thin films. This work provides new insights on the molecular design of topochemical reactions and paves the way for future applications of this fascinating family of materials.

Phase behaviors, properties and potential application of temperature-responsive microemulsions based on tropine ionic liquids

Compared with traditional microemulsion, stimulating stimulus-responsive microemulsion is more challenging to achieve. A temperature-responsive microemulsion was formulated and optimized by using the mixture of a series of tropine-based ionic liquids (TILs) and water as a polar phase, different aliphatic oils as a nonpolar phase, and an optimal mixture of nonionic surfactant Triton X-100 (TX-100) and different short-chain aliphatic alcohols as a cosurfactant. The results revealed that cyclohexane (as the nonpolar phase) had the better ability to combine with TX-100/1-octanol (mass ratio of 7:3) to form the TILs-based microemulsion, and that the range of monophasic region increased with the length of alkyl chain attached to the TILs cation group. The classic oil-in-water (O/W), liquid crystal (L), mixture of liquid crystal and bicontinuous (B.C.), B.C. and inverse water-in-oil (W/O) subregions were clarified by the conductivity method and rheological measurements. Adding the TILs helps the microemulsion form. The microemulsion was temperature-responsive, and with the increase of mass ratio m(TILs to H2O) and the side chain length of TILs, the sensitivity of the microemulsion to temperature decreased. Dynamic light scattering and electron electron microscopy revealed the formation of spherical droplets of approximately 2 to 5 nm in size in the W/O subregions with droplet size increasing with the increase of molar ratio R (TILs + H2O to mixed surfactant), mass ratio m(TILs to H2O) and TILs side chain length. Measurements of polarity and particle size showed that the TILs were dissolved into the core of the aqueous phase and, along with water, became the polar phase of the microemulsion. The microemulsion formation was driven by the hydrogen bonding between TX-100 and the polar phase. The TILs-based microemulsion could be used to prepare nanoparticles of silica with dimensions of 50–73 nm. This comprehensive study provides useful information for the development of analogous TILs-based microemulsions, and these temperature-responsive microemulsions have promising applications simply by treating the mass ratio m(TILs to H2O) and side chain length of TILs.

Self-assembly and complex formation of amphiphilic star and bottle-brush block copolymers.

We use molecular dynamics computer simulations to investigate complexation and clustering of branched polymers. In this study, we focus on star and bottle-brush polymers. In our investigation, we identify key factors governing cluster formation of branched amphiphilic polymers and provide guidance for designing and preparing various types of polymer clusters for applications, e.g., in drug delivery or materials science. We observe different kinds of clustering in the polymer systems. Our star polymers consist of several arms of hydrophilic core particles with hydrophobic particles attached to the end of each star arm. We observe that amphiphilic star polymers generally tend to form spherical complexes. In contrast to this, bottle-brush polymers exhibit a larger variety of complex structures. With large grafting density and large side arms, we also observe spherical polymer clusters; however, for low grafting density and shorter side chains, distinct clusters connected by bridging particles are formed. Furthermore, we observe membrane-like clustering of bottle-brush polymers. We employ two different clustering algorithms for further analysis of the obtained structures with respect to shape factors, pair correlation functions, and radii of gyration. We find that the hydrophobic parts of polymers play a crucial role in the formation of the resulting structures during self-assembly. The hydrophilic core parts in star polymers along with steric hindrance lead to a screening effect for the hydrophobic parts of the polymers. With bottle-brush copolymers, the hydrophilic parts of the polymers exhibit a screening effect that is sensitive to the grafting density and side chain lengths along the backbone.

Ionic liquid assisted nanocellulose production from microcrystalline cellulose: Correlation between cellulose solubility and nanocellulose yield via COSMO-RS prediction

The use of ionic liquids (ILs) in nanocellulose (NC) production from cellulosic materials has gained significant interest due to the intrinsic physical solubility of cellulosic materials in many ILs. However, given the numerous possible cation–anion combinations, selecting potential candidates from thousands of ILs for NC production is rather difficult. In addition, NC yield depends on the types of ILs and their capability in dissolution of cellulosic materials. In this study, we investigate NC production from microcrystalline cellulose (MCC) using various ILs as a reaction medium. Firstly, the prediction of MCC solubility in 300 ILs (15 cations and 20 anions) was obtained by deploying the conductor-like screening model for real solvents (COSMO-RS) which has emerged as a reliable and promising tool for solvents screening based on the dominant interactions of H-bonds, misfits, and Van der Waals energies of the fluid mixture. Experimental measurement of NC production from MCC in six ILs, namely [Emim][OAc], [Bmim][OAc], [Bmim][Cl], [Emim][HSO4], [Bmim][HSO4], and [Hmim][HSO4], was conducted. Based on the logarithmic activity coefficient prediction at infinite dilution, there was a negative correlation between cellulose solubility and experimental NC yield obtained. [Hmim][HSO4] IL showed the highest nanocellulose yield (65%) due to a relatively weaker H-bonding ability with cellulose. Moreover, the multiparameter scale of the Kamlet-Taft of six ILs revealed that the increase in alkyl side chain length of the IL cation resulted in a decrease of hydrogen bonding acidity, which contributed to higher NC yield. The quantitative prediction of COSMO-RS, coupled with the experimental study, can therefore be utilized to screen, and classify the potential ILs to prepare nanocellulose.

Dynamics of Bottlebrush Polymers in Solution by Neutron Spin Echo Spectroscopy

We present dynamical and morphological studies on poly(dimethylsiloxane) (PDMS)-based bottlebrush polymers in solution. A combination of small-angle neutron scattering (SANS), pulsed field gradient nuclear magnetic resonance (PFG NMR), and neutron spin echo (NSE) spectroscopy was used to identify structural changes inherent in changing the side-chain length while keeping the backbone constant. These morphological changes are mirrored in the diffusion coefficient determined by PFG NMR, resulting in two coefficients for the elongated and one for the more spherical sample. Faster motions are tracked by NSE using the advantage of time- and length-scale resolutions with the diffusion coefficient predetermined by PFG NMR. Hereby, the sample with short side chains relaxes like wormlike micelles considering the longitudinal direction, whereas the dynamics along the radial extension shows a much stronger Q-dependence as known from any theory. The dynamical behavior within the blob region, covered with the more spherical sample, follows the predictions of Zimm as well as of Zilman and Granek (ZG).

Functional characterization of maltodextrin glucosidase for maltodextrin and glycogen metabolism in Vibrio vulnificus MO6-24/O.

Glycogen is important for transmission of V. vulnificus undergoing disparate environments of nutrient-rich host and nutrient-limited marine environment. The malZ gene of V. vulnificus encoding a maltodextrin glucosidase was cloned and over-expressed in E. coli to investigate its roles in glycogen/maltodextrin metabolism in the pathogen. The malZ gene encoded a protein with a predicted molecular mass of 70kDa. The optimal pH and temperature of MalZ was 7.0 and 37°C, respectively. MalZ hydrolyzed maltodextrin to glucose and maltose most efficiently, while hydrolyzed other substrates such as starch, maltose, β-cyclomaltodextrin, and glycogen less efficiently. The activity was enhanced greatly by Mn2+. It also exhibited transglycosylation activity toward excessive maltotriose. The malZ knock-out mutant accumulated 2.3-5.6-fold less glycogen than the wild type when excessive maltodextrin or glucose was added to LB medium, while it accumulated more glycogen than the wild type (3.5-fold) in the presence of excessive maltose. Growth and glycogen accumulation of the mutant were retarded most significantly in the M63 minimal medium supplemented with 0.5% maltodextrin. Side chain length distributions of glycogen molecules were varied by the malZ mutation and types of the excessive carbon source. Based on the results, MalZ of V. vulnificus was likely to be involved in maltose/maltodextrin metabolism, thereby balancing synthesis of glycogen and energy generation in the cell. The bacterium seemed to have multiple and unique pathways for glycogen metabolism according to carbon sources.

Multi-spectroscopic characterization of bitumen and its polarity-based fractions

• Insights on H/C-ratio, aromatic systems and average molecular sizes are obtained. • NMR reveals varying chain lengths of aliphatic substituents throughout the fractions. • Characteristic NMR shifts in the resins suggest presence of some esters or amides. • 31 P NMR after derivatization, shows minor amounts of alcohols and carboxylic acids. Bitumen contains a complex mixture of molecules, ranging from simple linear alkanes to complex polyaromatic systems. Used in road construction, those structures are permanently influenced by atmospheric processes, which result in oxidation, degradation, loss of volatiles and structural rearrangements. In order to understand those molecular changes, a profound description of the unaltered system is needed. In this study, structural and chemical peculiarities of bitumen and its polarity-based fractions were analysed using nuclear magnetic resonance (NMR) techniques in combination with infrared/fluorescence spectroscopy and elemental analysis. The bitumen sample was separated into saturates, aromatics, resins and asphaltenes. Elemental analysis provided insights into variations of heteroatom content and hydrogen-carbon ratio among the fractions. Fluorescence spectroscopy showed an increase in the aromatic condensation degree with rising polarity. The combination of heteronuclear single quantum coherence (HSQC) and elemental analysis facilitated the assessment of length and branching extent of aliphatic side chains, throughout the fractions. Another 2D NMR technique, heteronuclear multiple bond coherence (HMBC) found evidence for minor contributions of carboxylic esters or amides within the resins. Hydroxyl and amino groups were analysed by 31 P NMR after derivatization, revealing minor amounts of alcohols, amides and carboxylic acids in the most polar fractions. Additionally, diffusion ordered spectroscopy was carried out to obtain estimations on average molecular sizes and weights. Applying in-depth NMR analysis to bitumen and combining it with complementary analytical techniques, this study provides a unique basis for future ageing studies and demonstrates how multi-spectroscopy can give new insights into bitumen structure and chemistry.

The Effects of Lengths of Flavin Surfactant N-10-Alkyl Side Chains on Promoting Dispersion of a High-Purity and Diameter-Selective Single-Walled Nanotube.

Flavin with defined helical self-assembly helps to understand chemical designs for obtaining high-purity semiconducting (s)-single-walled carbon nanotubes (SWNT) in a diameter (dt)-selective manner for high-end applications. In this study, flavins containing 8, 12, 16, and 20 n-alkyl chains were synthesized, and their single/tandem effects on dt-selective s-SWNT dispersibility were investigated at isomolarity. Flavins with n-dodecyl and longer chain lengths (FC12, FC16, and FC20) act as good surfactants for stable SWNT dispersions whereas n-octyl flavin (FC8) exhibits poor dispersibility owing to the lack of SWNT buoyancy. When used with small-dt SWNT, FC8 displays chirality-selective SWNT dispersion. This behavior, along with various flavin helical motifs, prompts the development of criteria for ‘side chain length (lS)’ required for stable and dt-selective SWNT dispersion, which also explains lS-dependent dt-enrichment behavior. Moreover, SWNT dispersions with flavins with dodecyl and longer lS exhibit increased metallic (m)-SWNT, background absorption-contributing carbonaceous impurities (CIs) and preferential selectivity of s-SWNT with slightly larger dt. The increased CIs that affect the SWNT quantum yield were attributed to a solubility parameter. Furthermore, the effects of flavin lS, sonication bath temperature, centrifugal speed, and surfactant concentration on SWNT purity and s-/m-SWNT ratio were investigated. A tandem FC8/FC12 provides fine-tuning of dt-selective SWNT dispersion, wherein the FC8 ratio governs the tendency towards smaller dt. Kinetic and thermodynamic assemblies of tandem flavins result in different sorting behaviors in which wide dt-tunability was demonstrated using kinetic assembly. This study highlights the importance of appropriate side chain length and other extrinsic parameters to obtain dt-selective or high-purity s-SWNT.

Thermal simulation experimental study on the difference of molecular structure evolution between vitrinite and inertinite in low-rank coal

In order to carry out an in-depth study of the differences in the molecular structure evolution of the vitrinite and the inertinite during coalification, the chemical structure of 13 groups of vitrinite and inertinite with different coal ranks were comprehensively characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and13C nuclear magnetic resonance (13C NMR). The correlation of structure parameters and vitrinite random reflectance (Ro, ran) were analyzed. The results show that three evolution stages of vitrinite were observed withRo, ranat 0.35%–0.90%, 1.20%–2.67%, and 3.03%–4.20%, and two evolution stages of inertinite were marked withRo, ranat 0.35%–2.07% and 2.07%–4.20%. Thefa, DOC, I,fa',faH,faN,faB, Xb, La, Lc, and Naveof inertinite are always larger than vitrinite, whereas the A(CH2)/(CH3),fal,fal*,falH, d002of inertinite are always smaller than vitrinite. WhenRo, ran= 0.35%–0.90%, the oxygen-containing functional groups and aliphatic structure of vitrinite fall off rapidly, the condensation degrees of the aromatic ring, La, Lc, and Naveincrease, whereas the lengths of side chains and d002decrease. WhenRo, ran= 1.20%–2.67%, the vitrinite structure variation follows the same trend as the first stage, but the evolution rate is significantly lower. WhenRo, ran= 0.35%–2.07%, the oxygen-containing functional groups, methyl groups, and methylene groups of inertinite fall off at a slower rate than those of vitrinite. The aromaticity, condensation degree, aromatic carbon content, and order degree of microcrystalline structure also increase at a rate less than that of vitrinite. The vitrinite and inertinite structure variation becomes flat, and the structures of both macerals are similar in the high metamorphic stage. The content of oxygen-containing functional groups and aliphatic chain length decrease to the lowest, whereas the aromaticity increases to the maximum. This study contributes to a comprehensive understanding of the chemical structure differences between vitrinite and inertinite, which can provide a theoretical reference for the clean utilization of coal and coalbed methane (CBM) exploration and development.