Side Chain Length Research Articles

Multifaceted Aspects of HIV-1 Nucleocapsid Inhibition by TAR-Targeting Peptidyl-Anthraquinones Bearing Terminal Aromatic Moieties.

2,6-dipeptidyl-anthraquinones are polycyclic planar systems substituted at opposite ring positions by short aminoacyl side chains. Derivatives with positively charged terminal amino acids showed in vitro inhibition of HIV-1 nucleocapsid (NC) protein correlating with threading intercalation through nucleic acid substrates. We found that the variation of the terminal amino acid into an aromatic moiety has profound effects on the NC inhibition of TAR–RNA melting, granting enhanced interaction with the protein. While all compounds showed appreciable NC and TAR binding, they exhibited different strengths driven by the length of the peptidyl side chains and by the stereochemistry of the terminal tyrosine. Unexpectedly, the best inhibitors of NC-induced TAR melting, characterized by the D- configuration of tyrosine, were able to form ternary complexes without competing with TAR–NC recognition sites, as shown by native mass spectrometry experiments. Furthermore, the hydrophobicity of the terminal residue enhances membrane permeation, with positive implications for further studies on these NC–TAR-targeted compounds.

Synthesis of tetramethylpiperidine 1-oxyl-based functional ionic liquids (FTILs), volumetric properties and thermodynamics of the activation for viscous flow of (FTILs + water) binary systems

The application of tetramethylpiperidine 1‑oxyl (TEMPO)-based ionic liquids is a newly emerging area in the fields of the extraction natural compounds. Herein, TEMPO-based functional ionic liquids (FTILs) [CnTr][TEMPO-OSO3] (n = 2, 4, 6, 8, 10, 12, 14, 16) were synthesized and characterized by FT-IR, 1H NMR, 13C NMR and high-resolution mass spectrometry. The volumetric properties and thermodynamics of the activation for viscous flow of (FTILs + water) binary systems were measured. Under the experimental conditions, with the increase of hydrophobic side chain length, the interaction between FTILs and solvent decreases and the interaction between FTILs ions and FTILs ions increases. The FTILs are water-structure-making solutes. The activation process of the solutes for viscous flow of the binary systems is an isocoulomb reaction. A semi-empirical method is an effective method to predict the viscosity of the binary systems within a certain concentration range (m < 0.9 mol·kg−1).

Protein-Resistant Amphiphilic Copolymers Containing Fluorosiloxane Side Chains with Controllable Length

Molecular-scale compositional heterogeneities can slash the nonspecific interaction between proteins and surfaces, resisting surface contamination. In this work, an amphiphilic copolymer containing a soft fluorosilicone macromonomer with controllable chain length as low-surface-energy hydrophobic component and a zwitterionic monomer as hydrophilic component was prepared to establish molecular-scale compositional heterogeneities. The length of the fluorosiloxane side chains can significantly impact the surface compositional heterogeneities, thus influencing the antifouling performance of the copolymer coatings. Even under water, the coating still retains a large number of low-surface-energy fluorosilicone segments on the surface. The balance between hydrophilic and hydrophobic segments on the surface provides a better synergistic effect, which endows the copolymer coatings with excellent resistance to various proteins.

Thermoresponsive Polyphosphoester via Polycondensation Reactions: Synthesis, Characterization, and Self-Assembly.

Using a novel strategy, amphiphilic polyphosphoesters based on poly(oxyethylene H-phosphonate)s (POEHP) with different poly(ethylene glycol) segment lengths and aliphatic alcohols with various alkyl chain lengths were synthesized using polycondensation reactions. They were characterized by 1H NMR, 13C {H} NMR 31P NMR, IR, and size exclusion chromatography (SEC). The effects of the polymer structure on micelle formation and stability, micelle size, and critical micelle temperature were studied via dynamic light scattering (DLS). The hydrophilic/hydrophobic balance of these polymers can be controlled by changing the chain lengths of hydrophilic PEG and hydrophobic alcohols. A solubilizing test, using Sudan III, revealed that hydrophobic substances can be incorporated inside the hydrophobic core of polymer associates. Loading capacity depends on the length of alkyl side chains. The results obtained indicate that these structurally flexible polymers have the potential as drug carriers.

Side Chain Length and Interaction Mediated Charge Transport Networks of Non-Fullerene Acceptors for Efficient Organic Solar Cells

Side Chain Length and Interaction Mediated Charge Transport Networks of Non-Fullerene Acceptors for Efficient Organic Solar Cells

Tunable Thin Film Periodicities by Controlling the Orientation of Cylindrical Domains in Side Chain Liquid Crystalline Block Copolymers

A facile approach to block copolymer (BCP) domain orientation control in thin films has been demonstrated by employing a BCP with liquid crystalline semifluorinated side chains by tuning the composition of the copolymers of the bottom surface layer (BSL). 1H,1H,2H,2H-Perfluorodecanethiol was attached to a precursor polymer, polystyrene-block-poly(glycidyl methacrylate) (PS-b-PGMA), to obtain a novel BCP with a C8F17-containing liquid crystal (LC) side chain (PS-b-P8FMA). Anisotropic hexagonally packed cylinder domains in a bulk state were first characterized by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The observed morphology transition of BCPs with different fluorinated side chain lengths of –CF3, –C4F9, and –C6F13 suggested the decisive effects of LC side chain ordering on the anisotropic nanostructures. In the thin film study, poly(methyl methacrylate-random-2,2,2-trifluoroethyl methacrylate-random-methacrylic acid) (PMMA-ran-PTFEMA-ran-PMAA) solution was used as BSLs for tuning the desired periodicities. The surface free energy (SFE) of BSL was simply tailored by changing the composition of comonomers. In atomic force microscopy (AFM) characterization, long-range ordered perpendicularly oriented BCP domains in a hexagonally packed array or parallel oriented BCP domains as striation patterns were easily fabricated on non-preferential or preferential BSL, respectively. The study presents a novel approach to tunable thin film periodicities without changing or modifying BCPs, which is desired in next-generation BCP lithography.

Recombinant Extracellular Cholesterol Oxidase from Nocardioides simplex.

Cholesterol oxidase is a highly demanded enzyme used in medicine, pharmacy, agriculture, chemistry, and biotechnology. It catalyzes oxidation of 3β-hydroxy-5-ene- to 3-keto-4-ene- steroids with the formation of hydrogen peroxide. Here, we expressed 6xHis-tagged mature form of the extracellular cholesterol oxidase (ChO) from the actinobacterium Nocardioides simplex VKM Ac-2033D (55.6 kDa) in Escherichia coli cells. The recombinant enzyme (ChONs) was purified using affinity chromatography. ChONs proved to be functional towards cholesterol, cholestanol, phytosterol, pregnenolone, and dehydroepiandrosterone. Its activity depended on the structure and length of the aliphatic side chain at C17 atom of the steroid nucleus and was lower with pregnenolone and dehydroepiandrosterone. The enzyme was active in a pH range of 5.25÷6.5 with the pH optimum at 6.0. Kinetic assays and storage stability tests demonstrated that the characteristics of ChONs were generally comparable with or superior to those of commercial ChO from Streptomyces hygroscopicus (ChOSh). The results contribute to the knowledge on microbial ChOs and evidence that ChO from N. simplex VKM Ac-2033D is a promising agent for further applications.

Impact of Side-Chain Hydrophilicity on Packing, Swelling, and Ion Interactions in Oxy-Bithiophene Semiconductors.

Exchanging hydrophobic alkyl-based side chains to hydrophilic glycol-based side chains is a widely adopted method for improving mixed-transport device performance, despite the impact on solid-state packing and polymer-electrolyte interactions being poorly understood. Presented here is a molecular dynamics (MD) force field for modeling alkoxylated and glycolated polythiophenes. The force field is validated against known packing motifs for their monomer crystals. MD simulations, coupled with X-ray diffraction (XRD), show that alkoxylated polythiophenes will pack with a "tilted stack" and straight interdigitating side chains, whilst their glycolated counterpart will pack with a "deflected stack" and an s-bend side-chain configuration. MD simulations reveal water penetration pathways into the alkoxylated and glycolated crystals-through the π-stack and through the lamellar stack respectively. Finally, the two distinct ways triethylene glycol polymers can bind to cations are revealed, showing the formation of a metastable single bound state, or an energetically deep double bound state, both with a strong side-chain length dependence. The minimum energy pathways for the formation of the chelates are identified, showing the physical process through which cations can bind to one or two side chains of a glycolated polythiophene, with consequences for ion transport in bithiophene semiconductors.

Mechanism and Kinetics of the Reaction of Nitrate Radicals with Carboxylic Acids.

Rate constants for the reaction of nitrate radical (NO3 ⋅) with several carboxylic acids (RCO2 H) were measured in acetonitrile using laser flash photolysis, and found to be on the order of 105 -106 M-1 s-1 . No observable H/D kinetic isotope effect was observed at the carboxyl O-H group, α-C-H bond and (possibly) in the case of formic acid, the formylic C-H bond. This suggests that NO3 ⋅ does not abstract hydrogen from any of these positions despite the fact that all these processes are thermodynamically favorable. Reactivity increases with increased length and/or branching of the alkyl side chain (R), and approaches, but does not quite reach, that of an alkane towards NO3 ⋅. The relative inertness of carboxylic acids towards NO3 ⋅ can be explained by the polar effect.

Brain ethanolamine phospholipids, neuropathology and cognition: A comparative post-mortem analysis of structurally specific plasmalogen and phosphatidyl species.

Reduced cognition in the elderly is associated with low levels of plasmalogens and high levels of lipid rafts, amyloid plaques, and neurofibrillary tangles in the temporal cortex. A systematic integrative analysis of key indices of these pathologies to determine their collective and independent contributions to cognition was performed. Levels of four phosphatidylethanolamines (PE) and four ethanolamine plasmalogens (PL) of identical sn-1 carbon length and desaturation (stearic, 18:0) and identical sn-2 fatty acid compositions of varying side chain lengths and degrees of unsaturation (oleic, 18:1; linoleic, 18:2; arachidonic, 20:4; docosahexaenoic, 22:6), flotillin-1 expression and amyloid plaque and neurofibrillary tangle densities were measured in inferior temporal cortex tissue from 100 elderly subjects (Rush University Memory and Aging Project, 88.5 ± 5.8 years old). Subjects were evenly distributed with respect to gender (52/48, F/M) and cognitive status (38/24/38, no cognitive impairment/mild cognitive impairment/Alzheimer’s dementia) proximate to death. Multivariate logistic regression analyses were used to determine the relative and collective associations of the neuropathological indices with cognition. Higher levels of tangles, amyloid, or flotillin and lower levels of PL 18:0/22:6 were significantly associated with lower cognition in the base model (adjusted for age, sex, education). Multivariate analysis revealed that only PL 18:0/22:6 (β = 0.506; p < 0.00001), tangles (−0.307; p < 0.01), and flotillin (−0.2027; p < 0.05) were independently associated with reduced cognition. PL 18:0/22:6 and PE 18:0/22:6 levels were independently associated with cognition in the presence of tangles, amyloid, and flotillin, but only PL 18:0/22:6 retained its association with cognition when both PL and PE 18:0/22:6 were included in the model indicating that PE 18:0/22:6 levels were associated with PL 18:0/22:6, not cognition. Only high brain levels of PL 18:0/22:6 (>mean+1SD) was predictive of normal cognition (coef = 1.67, p < 0.05) and non-demented state (coef = −2.73, p < 0.001), whereas low levels of PL 18:0/22:6 and high levels of tangles or flotillin were predictive of dementia. The association of high brain polyunsaturated (PUFA)-PL levels with better cognition was independent of amyloid plaque, neurofibrillary tangle, PE, and flotillin-1 expression. Maintenance or augmentation of brain docosahexaenoic (DHA)-PL levels warrants further investigation as a target for preventing cognitive decline or improving cognition in the elderly, respectively.

Synthesis of fully divanillic acid-based aromatic polyamides and their thermal and mechanical properties

Fully divanillic acid (DVA)-based aromatic polyamides (R-R′-DVAPAs) having methyl or butyl side chains (R = -(CH2)n-1-CH3; n = 1 or 4) with weight-average molecular weights ranging from 49,000 to 60,000 g mol−1 were synthesized by polycondensation of alkylated DVA-based dicarboxylic acid monomers and diamine monomers. Thermogravimetric analysis of the polyamides found decomposition temperatures at approximately 380 °C and glass transition temperatures of 207 °C–262 °C, depending on the side-chain length, indicating high heat resistance and thermal stability. Differential scanning calorimetry and dynamic mechanical analysis revealed an amorphous structure for the DVAPAs. The DVAPAs showed good solubility in common polar organic solvents, although cast films prepared from dimethylformamide solution were brittle. Thermo-pressed films were prepared at temperatures higher than the glass transition temperature. The film of Bu-Bu′-DVAPA, which has butyl side chains along the fully aromatic main chain, exhibited a maximum tensile strength of approximately 40 MPa. These polyamides are promising as fully bio-based aromatic high-performance plastics.

Synthesis of Polycarboxylate Viscosity Reducer and the Effect of Different Chain Lengths of Polyether on Viscosity Reduction of Heavy Oil.

Since there are not many studies on the application of polymeric surfactants in viscosity reduction emulsification of heavy oil, a series of polyether carboxylic acid–sulfonate polymeric surfactants were synthesized. The viscosity reduction performance and the effect of different chain lengths on the viscosity reduction effect were also investigated. The viscosity reduction, emulsification, wetting, and foaming performance tests showed that the viscosity reduction performance of this series of polymeric surfactants was excellent, with the viscosity reduction rate exceeding 95%, and the viscosity was reduced to 97 mPa·s by the polymeric surfactant with a molecular weight of 600 polyethers. It was also concluded that among the three surfactants with different side chains, the polymeric surfactant with a polyether molecular weight of 600, which is the medium side-chain length, had the best viscosity reduction performance. The study showed that the polyether carboxylic acid–sulfonate polymer surfactant had a promising application in the viscosity reduction of heavy oil.

Synthesis and thermoresponsive behavior of double hydrophilic graft copolymer based on poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline)

A recent challenge in polymer self-assembly is the utilization of double hydrophilic graft copolymers (DHGC) in view of biomedical applications. Here we describe, for the first time, a platform of biocompatible DHGC fully based on poly(2-alkyl-2-oxazoline) leading to stimuli-responsive self-assemblies. This original DHGC platform was composed of backbone poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline) (P(MeOx-co-PentOx)) and poly(2-ethyl-2-oxazoline) (PEtOx) grafts. A “grafting onto” approach based on the combination of cationic ring-opening polymerization (CROP) technique and “click chemistry” CuAAc reaction, was successfully used to synthesize poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline)-g-poly(2-ethyl-2-oxazoline) (P(MeOx-co-PentOx)-g-PEtOx) copolymer conjugates of varying backbone and side chain lengths. These purely hydrophilic copolymers demonstrated self-assembling behavior in aqueous solution, showing a characteristic double hydrophilic behavior originating from building blocks immiscibilities. Self-associated structures with spherical morphologies have been evidenced by DLS and cryo-TEM. The sizes and the efficiency of self-association were mainly controlled by the concentration of the graft copolymer and by the molar ratio of the different hydrophilic compounds. In addition, thermoresponsive properties of these copolymers were studied by turbidimetry and DLS. From purely hydrophilic at low temperature, the copolymers showed amphiphilic characters at temperatures close to the cloud points (CP). Interestingly, cloud points were not controlled by the PEtOx graft length as it has been reported for PEtOx homopolymers but it depended mainly upon the PEtOx content of the copolymer, with a critical value around 75 PEtOx wt%. Addition of a kosmotropic salt (Na2SO4) allowed to trigger CPs from 80 °C till 26 °C. The self-assembling properties of this family of hydrophilic and biocompatible copolymers may offer promising prospect in the field of biomedical applications as bioreactors.

Whole-exome sequencing expands the roles of novel mutations of organic anion transporting polypeptide, ATP-binding cassette transporter, and receptor genes in intrahepatic cholestasis of pregnancy.

Background: Intrahepatic cholestasis of pregnancy (ICP) is associated with a high incidence of fetal morbidity and mortality. Therefore, revealing the mechanisms involved in ICP and its association with fetal complications is very important. Methods: Here, we used a whole-exome sequencing (WES) approach to detect novel mutations of organic anion transporting polypeptide (OTAP) genes, ATP-binding cassette transporter (ABC) genes, and receptor genes associated with ICP in 249 individuals and 1,029 local control individuals. Two available tools, SIFT and PolyPhen-2, were used to predict protein damage. Protein structuremodeling and comparison between the reference and modified protein structures were conducted by SWISS-MODEL and Chimera 1.14rc software, respectively. Results: A total of 5,583 mutations were identified in 82 genes related to bile acid transporters and receptors, of which 62 were novel mutations. These novel mutations were absent in the 1,029 control individuals and three databases, including the 1,000 Genome Project (1000G_ALL), Exome Aggregation Consortium (ExAC), and Single-Nucleotide Polymorphism Database (dbSNP). We classified the 62 novel loci into two groups (damaging and probably damaging) according to the results of SIFT and PolyPhen-2. Out of the 62 novel mutations, 24 were detected in the damaging group. Of these, five novel possibly pathogenic variants were identified that were located in known functional genes, including ABCB4 (Ile377Asn), ABCB11 (Ala588Pro), ABCC2 (Ile681Lys and Met688Thr), and NR1H4 (Tyr149Ter). Moreover, compared to the wild-type protein structure, ABCC2 Ile681Lys and Met688Thr protein structures showed a slight change in the chemical bond lengths of ATP-ligand binding amino acid side chains. The combined 32 clinical data points indicate that the mutation group had a significantly (p = 0.04) lower level of Cl ions than the wild-type group. Particularly, patients with the 24 novel mutations had higher average values of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), total bile acids (TBA), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) than patients with the 38 novel mutations in the probably damaging group and the local control individuals. Conclusion: The present study provides new insights into the genetic architecture of ICP involving these novel mutations.

On the Stability of Non‐fullerene Acceptors and Their Corresponding Organic Solar Cells: Influence of Side Chains

AbstractSide chain engineering is a widely explored strategy in the molecular design for non‐fullerene acceptors (NFAs). Although the relationship between side chain structures and optoelectronic properties of NFAs is well clarified, the effect of side chain structures on the stability of NFAs and their corresponding organic solar cells (OSCs) is rarely reported. Herein, a series of Y‐family NFAs with varying side‐chains are studied to investigate their degradation upon multiple stresses including water, oxygen from ambient, chemical environment from ZnO electron transport layer, temperature, and ultraviolet light. The results show that all of these Y‐family NFAs are highly stable against water and oxygen in ambient dark condition, while their photochemical and thermal stabilities decrease with the increasing side chain length. NFAs with shorter side chains are not only more resistant to photo‐oxidation and photocatalytic reactions, but also can hamper the formation of large phase‐separated NFA domains upon storage in both glovebox and ambient conditions. As such, the PM6:NFA OSC with short side‐chain NFA also exhibits superior operational stability, associating with a higher T80 lifetime. This study demonstrates that the side chains must be considered to obtain stable OSCs.

Disrupting Effects of Osteogenesis Imperfecta Mutations Could Be Predicted by Local Hydrogen Bonding Energy.

Osteogenesis imperfecta(OI) is a disease caused by substitution in glycine residues with different amino acids in type I collagen (Gly-Xaa-Yaa)n. Collagen model peptides can capture the thermal stability loss of the helix after Gly mutations, most of which are homotrimers. However, a majority of natural collagen exists in heterotrimers. To investigate the effects of chain specific mutations in the natural state of collagen more accurately, here we introduce various lengths of side-chain amino acids into ABC-type heterotrimers. The disruptive effects of the mutations were characterized both experimentally and computationally. We found the stability decrease in the mutants was mainly caused by the disruption of backbone hydrogen bonds. Meanwhile, we found a threshold value of local hydrogen bonding energy that could predict triple helix folding or unfolding. Val caused the unfolding of triple helices, whereas Ser with a similar side-chain length did not. Structural details suggested that the side-chain hydroxyl group in Ser forms hydrogen bonds with the backbone, thereby compensating for the mutants’ decreased stability. Our study contributes to a better understanding of how OI mutations destabilize collagen triple helices and the molecular mechanisms underlying OI.

Lipophilic phenanthroline diamide ligands in 1-octanol for separation of Am(III) from Eu(III)

Although phenanthroline diamide (DAPhen) ligands have recently shown vast opportunity in group separation of actinides, the commonly used diluents in research, such as cyclohexanone with highly aqueous intersolubility, and 1-(trifluoromethyl)− 3-nitrobenzene with strong toxicity and corrosiveness, are becoming clear demerits. Herein, several lipophilic N,N′-dialkyl-N,N′-diphenyl-2,9-diamide-1,10-phenanthroline (R-Ph-DAPhen) ligands were synthesized and employed for selective separation of Am(III) from Eu(III) in 1-octanol, a practical low-toxicity and low-corrosive solvent. The solvent extraction results confirm their separation effect toward Am(III) over Eu(III) in both 1-octanol and TBP/1-octanol (v/v, 3/7) systems. Spectroscopic analysis illustrates that the ligands simultaneously generate M:L= 1:1 and 1:2 complexes with Ln(III), depending on the molar ratio of metal ion to ligand. The steric hindrance caused by the length of the alkyl side chains greatly affects the coordination chemistry of these ligands. Density functional theory (DFT) calculations shed light that these R-Ph-DAPhen ligands have desired An(III) affinity over Ln(III), and compared with F-3 solvent, 1-octanol weakens the extraction ability of the ligands for both lanthanides and actinides. This work contributes to further understanding of the extraction behavior of phenanthroline diamide-based ligands in different solvents and pushing them forward into practical applications in real An(III) extraction.

Comb-shaped polyfluorene with variable alkyl chain length for application as anion exchange membranes

To fabricate anion exchange membranes (AEMs) with high ionic conductivity and excellent chemical stability, in this study, we develop a series of comb-shaped polyfluorene copolymers with side chains of different lengths by superacid-catalyzed Friedel-Grafts polycondensation. Direct introduction of comb-shaped alkyl side chains induce obvious micro-phase separation in these AEMs, as confirmed by atomic force microscopy. PHPFP-QA with the longest side chain has the lowest IEC and the highest ionic conductivity (24.3 mS cm−1 at 20 °C) and power density (596 mW cm−2 at 80 °C) because of its loose structure, which causes more water to be absorbed and a greater hydration number (λ). Owing to a stable piperidinium cation and ether-free backbones, these polyfluorene-based AEMs exhibit excellent alkaline stability. The conductivities of PMPFP-QA, PBPFP-QA, and PHPFP-QA decrease by approximately 23%, 21%, and 17% after immersing them in 2 M KOH at 80 °C for 30 days, respectively. Hence, polyfluorene grafting with comb-shaped side chains can be used to design alkaline electrochemical energy conversion and storage devices.

Influence of Ionic Liquids on the Aggregation and Pre-aggregation Phenomena of Asphaltenes in Model Solvent Mixtures by Molecular Dynamics Simulations and Quantum Mechanical Calculations

This work presents a systematic study of asphaltene pre-aggregation phenomena in the absence and in the presence of ionic liquids (ILs) from the family of 1-alkyl-3-methylimidazolium by molecular dynamics simulations. The effects of the alkyl chain length of the cation (studying ILs with alkyl chains between C4 and C10) and of the dimension of the anion (testing chloride and bromide) on the aggregation behavior of asphaltenes have been studied. To correlate the results obtained with the direct interaction between each additive and asphaltene, the latter was investigated both by the analysis of the radial distribution functions obtained by molecular dynamics simulations and quantum mechanical calculations. The DFT method was used to calculate the relative stability of the asphaltene-ionic liquid dimers and also the energy, shape, and spatial distribution of frontier orbitals. It was found that all the ionic liquids studied present a dispersing effect on asphaltene in model solvents, except for mixtures rich in toluene where, in most cases, the opposite effect is observed. This is accompanied by the interaction intensity as measured by radial distribution functions. The effects of the alkyl side chain length of the cation and of the anion radius are subtler, but it seems that the asphaltene dispersion effect increases with the length of the cation’s alkyl side chain and decreases with the radius of the anion; these effects are more clearly observed in the mixtures richer in n-heptane. These trends were corroborated by DFT calculations, which showed that the energetic stability of the asphaltene-additive dimer is as higher as the alkyl chain is longer and the anion is smaller. Pre-aggregation phenomena were also studied in mixtures containing CO2, which proved to be a precipitating agent as observed experimentally. The relative performances of the IL studied were not altered by the presence of CO2.

Impact of Conjugated Polymer Characteristics on the Enrichment of Single-Chirality Single-Walled Carbon Nanotubes

Polymer characteristics influence the chiral selectivity and yield in the enrichment of (7,6) from Signis SG76 in toluene by various fluorene homopolymers and copolymers. Fluorene homopolymers such as poly(9,9-di-n-dodecylfluorene) (PFDD) and copolymers with anthracene such as poly[(9,9-dihexylfluorenyl-2,7-diyl)-co-(9,10-anthracene)] (PFH-A) result in high (7,6) selectivities of up to 67 and 72%, respectively. The selectivity is calculated by optical absorption using a known extinction coefficient and also evaluated by Raman scattering and photoluminescence excitation. In contrast, poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-(9,10-anthracene)] (PFO=A), with a double-bond spacer, results in (9,5) dominant extractions with the purity of (9,5) up to 80% after ultracentrifugation, which is believed to be the first report on the successful enrichment of (9,5) by conjugated polymers. The chiral selectivity is also greatly impacted by the length of alkyl side chain of fluorene homopolymers: hexyl group has low selectivity, while octyl, dodecyl, and tetradecyl (PFTD) groups show high selectivity toward (7,6), and the octadecyl group is prone to include bigger tubes. Interestingly, a chiral selection transition from (7,6) to (8,6) occurred using PFTD after a few enrichment cycles. The chiral purity of (8,6) was greatly improved from 50 to 86% after slow filtration. Polymer molecular weight (MW, here PFDD) also plays a role in the selectivity and yield. Low MW leads to a low yield, and high MW leads to a low selectivity, with the optimal range (Mn) being ca. 20–35 kDa when the polydisperse index is ca. 2–3. Molecular dynamics simulation confirms that different lengths of side chain of polyfluorene have different wrapping stabilities toward specific chirality, where PFTD shows greater stability toward (8,6) than (7,6).