Branched Alkyl Chains Research Articles

Optimal extent of fluorination enabling strong temperature-dependent aggregation, favorable blend morphology and high-efficiency polymer solar cells

Temperature-dependent aggregation is a key property for some donor polymers to realize favorable bulk-heterojunction (BHJ) morphologies and high-efficiency (>10%) polymer solar cells. Previous studies find that an important structural feature that enables such temperature-dependent aggregation property is the 2nd position branched alkyl chains sitting between two thiophene units. In this report, we demonstrate that an optimal extent of fluorination on the polymer backbone is a second essential structural feature that enables the strong temperature-dependent aggregation property. We compare the properties of three structurally similar polymers with 0, 2 or 4 fluorine substitutions in each repeating unit through an in-depth morphological study. We show that the non-fluorinated polymer does not aggregate in solution (0.02 mg mL−1 in chlorobenzene) at room temperature, which results in poor polymer crystallinity and extremely large polymer domains. On the other hand, the polymer with four fluorine atoms in each repeating unit exhibits an excessively strong tendency to aggregate, which makes it difficult to process and causes a large domain. Only the polymer with two fluorine atoms in each repeating unit exhibits a suitable extent of temperature-dependent aggregation property. As a result, its blend film achieves a favorable morphology and high power conversion efficiency. This provides another key design rationale for developing donor polymers with suitable temperature-dependent aggregation properties and thus high performance.

Influence of Substituent Chain Branching on the Transfection Efficacy of Cyclopropenium-Based Polymers.

The realization of gene therapy relies on the development of delivery vectors with high efficiency and biocompatibility. With a multitude of structures accessible, the core challenge is precisely tuning vector structure to probe and optimize structure–property relationships. Employing a modular strategy, two pairs of cationic polymers based on the trisaminocyclopropenium (TAC) ion were synthesized where the substituents differ in the degree of alkyl chain branching. All TAC-based polymers exhibited higher transfection efficiencies than the untreated controls, with variable in vitro toxicities. Considering both cytotoxicity and transfection efficacy, an optimal nonviral vector was identified. Our studies highlight the importance of exercising precise control over polymer structure, both in terms of backbone identity and substituent nature, and the necessity of a robust, modular platform from which to study them.

The impact of ion-pairing reagents on the selectivity and sensitivity in the analysis of modified oligonucleotides in serum samples by liquid chromatography coupled with tandem mass spectrometry

Present study highlights the usage of various ion-pairing agents and their impact on the process of separation and ionization of oligonucleotides in the fortified human serum samples. What is more, retention studies involved different stationary phases, including: octadecyl, phenyl, pentafluorophenyl groups and ligands with embedded polar groups. It was proved that retention of oligonucleotides strongly depends on the alkyl chain branching in the structure of ion pairing reagent. Furthermore ion-pairing agents build of straight alkyl chain are more easily adsorbed on the stationary phase modified with octadecyl groups, while branching of alkyl chain caused more effective adsorption of studied compounds at phenyl groups compared to octadecyl ones. The lowest limit of quantification values were obtained for 5mMN,N-dimethylbutylamine, while the highest values are characteristic for hexylamine. Moreover it was shown that a 2-fold increase of ion-pairing agent concentration results in higher LOQ. The greatest sensitivity was obtained for 2.5mMN,N-dimethylbutylamine/150mM hexafluoroisopropanol. On the other hand Hypersil GOLD aQ column was the most appropriate in terms of time and separation effectiveness. The developed method was successfully used for the determination of studied oligonucleotides and their metabolites in human serum samples. The compounds were separated in just 3.5min with high sensitivity (0.09–0.16ng).

Effect of inorganic alkalis on interfacial tensions of novel betaine solutions against crude oil

The effects of inorganic alkalis on the dynamic interfacial tensions (IFTs) of three betaine surfactants with different structures against daqing crude oil and model oils containing crude oil fractions, such as saturate, aromatic, resin, asphaltene and acidic fractions, have been studied by spinning drop tensiometer. The influences of pH value (alkali concentration and types) have been investigated. On the basis of the experimental results, one can find that it is difficult to reach the ultralow IFT value for all betaine solutions because of the mismatching of the hydrophilic head and hydrophobic tail. The unsaturated and branched alkyl chain can enlarge the size of hydrophobic part and reduce the equilibrium IFTs. By adding alkali, the IFTs are controlled by the mixed adsorptions of the petroleum acids, produced soaps and betaine molecules. For betaines with small hydrophobic part, 18C and 22C, the mixed adsorption films are compact than those of pure betaine films, which results in the decrease of IFT. On the other hand, the petroleum acids and soaps adsorb competitively with betaine molecules, due to the tighter packing of 26C molecules at the interface, the equilibrium IFT values of 26C increase with an increase in pH value. The stronger the alkali is, the better the synergism or antagonism is. The effects of pH on the IFTs of betaine solutions against model oils containing crude oil fractions agree with those against crude oil. For all betaines, the order of the ability of affecting IFT is acidic fractions > resin > asphaltene > aromatic > saturate in general.

Charge mobility enhancement for diketopyrrolopyrrole-based conjugated polymers by partial replacement of branching alkyl chains with linear ones

Side-chain engineering of three new conjugated D–A terpolymers by varying the number of branching and linear alkyl chains is presented for OFET studies.

Liquefaction-induced emission enhancement of tetraphenylethene derivatives.

A typical AIE dye, TPE, was liquefied by attaching long and branched alkyl chains. The obtained liquid dye showed intense emission compared to the solid dye or TPE. The linkage between TPE and the alkyl chain led to significant difference in their photoluminescent and thermal properties.

Comparative study of the intermolecular dynamics of imidazolium-based ionic liquids with linear and branched alkyl chains: OHD-RIKES measurements.

This article describes a comparative study of the low-frequency (0-450 cm-1) Kerr spectra of the branched 1-(iso-alkyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([(N - 2)mCN-1C1im][NTf2] with N = 3-7) ionic liquids (ILs) and that of the linear 1-(n-alkyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([CNC1im][NTf2] with N = 2-7) ILs. The spectra were obtained by use of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The intermolecular spectrum of a branched IL is similar to that of a linear IL that is of the same alkyl chain length rather than of the same number of carbon atoms in the alkyl chain. This similarity and the lack of a correlation of the first spectral moments and widths of the intermolecular spectra with chain length is mainly attributed to the increase in the dispersion contribution to the total molar cohesive energy being compensated by stretching of the ionic network due to the increasing size of the nonpolar domains, which is dependent only on the length of the alkyl chain.

The influence of branched alkyl side chains in A–D–A oligothiophenes on the photovoltaic performance and morphology of solution-processed bulk-heterojunction solar cells

Besides providing sufficient solubility, branched alkyl chains also affect the film-forming and packing properties of organic semiconductors.

Selective Cross-Coupling of (Hetero)aryl Halides with Ammonia To Produce Primary Arylamines using Pd-NHC Complexes

Herein we report the first example of (hetero)arylation of ammonia using a monoligated palladium-NHC complex. The new, rationally designed, precatalyst (DiMeIHeptCl)Pd(allyl)Cl featuring highly branched alkyl chains has been shown to be effective in selective aminations across a range of challenging substrates, including nitrogen-containing heterocycles and those featuring base-sensitive functionality. The less bulky Pd-PEPPSI-IPentCl precatalyst performs well for ortho-substituted aryl halides, giving monoarylated products in high yield with good selectivity.

Chemical and Radiation Stability of Ionic Liquids: A Computational Screening Study

Using a variety of density functional theory (DFT) methods, we present a systematic computational screening effort to analyze the chemical and radiation stability for a large number of anions and cations that constitute room-temperature ionic liquids (RTILs). We compute various electronic properties such as the HOMO–LUMO gap, the ionization potential, and the electron affinities for a large library of ions (42 cations and 42 anions). The theoretical analysis provides the most comprehensive characterization of the chemical and radiation stability of individual ions in RTILs to date. Our calculations reveal that cation stability is closely related to constituent alkyl chain length and branching, whereas the anion stability is mostly dictated by ion size and electronegativity. Furthermore, these calculations show that the ωB97XD functional is the most internally consistent for predicting the chemical and radiation stability. These calculations establish a chemical stability database and a theoretical procedu...

Effect of C9H12 alkylbenzenes on particle formation in diffusion flames: An experimental study

The sooting tendency of three C9H12 isomers, specifically n-propylbenzene, iso-propylbenzene and 1,3,5-trimethylbenzene (also known as mesitylene), was studied in atmospheric pressure, counter-flow diffusion flames of ethylene, whose fuel stream was doped with C9H12 isomers, added such that 10%, 20% and 30% of the total carbon was fed as aromatic carbon. In-situ spectroscopy, namely broadband UV-laser induced fluorescence, was used as diagnostic tool to detect combustion-formed nanoparticles whereas laser induced incandescence was used to detect soot particles. Experimental results were compared to those obtained in an ethylene/toluene flame operated in the same conditions in order to highlight the effect of the alkyl chain length and chain branching on particulate formation.The experimental results show that the longer and branched is the side alkyl chain (iso-propylbenzene with respect to n-propylbenzene) the higher is particle formation enhancement. Moreover, increasing the number of methyl groups attached to the aromatic ring (mesitylene compared with xylenes and toluene) does not result in enhanced sooting tendency in the analyzed combustion conditions.

Which Molecular Features Affect the Intrinsic Hepatic Clearance Rate of Ionizable Organic Chemicals in Fish?

Greater knowledge of biotransformation rates for ionizable organic compounds (IOCs) in fish is required to properly assess the bioaccumulation potential of many environmentally relevant contaminants. In this study, we measured in vitro hepatic clearance rates for 50 IOCs using a pooled batch of liver S9 fractions isolated from rainbow trout (Oncorhynchus mykiss). The IOCs included four types of strongly ionized acids (carboxylates, phenolates, sulfonates, and sulfates), three types of strongly ionized bases (primary, secondary, tertiary amines), and a pair of quaternary ammonium compounds (QACs). Included in this test set were several surfactants and a series of beta-blockers. For linear alkyl chain IOC analogues, biotransformation enzymes appeared to act directly on the charged terminal group, with the highest clearance rates for tertiary amines and sulfates and no clearance of QACs. Clearance rates for C12-IOCs were higher than those for C8-IOC analogues. Several analogue series with multiple alkyl chains, branched alkyl chains, aromatic rings, and nonaromatic rings were evaluated. The likelihood of multiple reaction pathways made it difficult to relate all differences in clearance to specific molecular features the tested IOCs. Future analysis of primary metabolites in the S9 assay is recommended to further elucidate biotransformation pathways for IOCs in fish.

Conjugated Donor–Acceptor Polymers Entailing Pechmann Dye-Derived Acceptor with Siloxane-Terminated Side Chains Exhibiting Balanced Ambipolar Semiconducting Behavior

We present four conjugated donor–acceptor (D–A) polymers PBPDT-Si, PBPDSe-Si, PBPDT, and PBPDSe entailing a new electron acceptor Pechmann dye framework, i.e., bipyrrolylidene-2,2′(1H,1′H)-dione (BPD), and thiophene and selenophene as the respective electron donors. PBPDT-Si and PBPDSe-Si contain siloxane-terminated side chains, while PBPDT and PBPDSe bear branching alkyl chains. The respective HOMO energies of PBPDT-Si and PBPDSe-Si are slightly higher than those of PBPDT and PBPDSe, whereas the respective LUMO energies of PBPDT-Si and PBPDSe-Si are slightly lower than those of PBPDT and PBPDSe. The results reveal that (i) thin films of all four polymers show ambipolar semiconducting performances under a nitrogen atmosphere, (ii) hole and electron mobilities are more balanced for PBPDT-Si and PBPDSe-Si, and (iii) the employment of siloxane-terminated side chains is beneficial for improving charge transporting compared to branching alkyl side chains. Thin film hole and electron mobilities of PBPDT-Si can ...

Metal-Ion-Induced Switch of Liquid-Crystalline Orientation of Metallomacrocycles.

A new series of shape-persistent imine-bridged macrocycles were synthesized based on dynamic covalent chemistry. The macrocycles had an alternating sequence of dibenzothiophene and N,N'-bis(salicylidene)-ethylenediamine (salen) tethering branched alkyl chains. The macrocycles and tetranuclear metallomacrocycles bearing long and branched alkyl chains exhibited thermotropic columnar liquid-crystalline phases over a wide temperature range and the metallomacrocycles greatly depended on the characteristics of the coordinated metal ions. The metal-free macrocycle showed a liquid-crystalline phase with a lamellar structure and poor birefringence. In sharp contrast, the macrocyclic Ni complex showed a columnar oblique liquid-crystalline phase, whereas the Pd and Cu complexes showed columnar liquid-crystalline phases with a lamellar structure. The macroscopic organization and thermal properties of the corresponding liquid-crystalline metallomacrocycles were significantly dependent on the subtle structural differences among the planar macrocycles, which were revealed by single-crystal X-ray crystallographic analysis of the macrocycles with shorter alkyl chains.

Non-ionic surfactant phase diagram prediction by recursive partitioning.

A model has been designed to predict the phase which forms in water for a non-ionic surfactant, at a given concentration and temperature. The full phase diagram is generated by selecting enough data points to cover the region of interest. The model estimates the probability for each one of 10 possible phases and selects the one with the highest likelihood. The probabilities are based on the recursive partitioning of a dataset of 10 000 known observations. The model covers alkyl chain length and branching, ethoxylate head length and number, and end capping of one or more of the ethoxylate chains. The relationship between chemical structure, shape and phase behaviour is discussed.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

Structures of Plutonium(IV) and Uranium(VI) with N,N-Dialkyl Amides from Crystallography, X-ray Absorption Spectra, and Theoretical Calculations.

The structures of plutonium(IV) and uranium(VI) ions with a series of N,N-dialkyl amides ligands with linear and branched alkyl chains were elucidated from single-crystal X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and theoretical calculations. In the field of nuclear fuel reprocessing, N,N-dialkyl amides are alternative organic ligands to achieve the separation of uranium(VI) and plutonium(IV) from highly concentrated nitric acid solution. EXAFS analysis combined with XRD shows that the coordination structure of U(VI) is identical in the solution and in the solid state and is independent of the alkyl chain: two amide ligands and four bidentate nitrate ions coordinate the uranyl ion. With linear alkyl chain amides, Pu(IV) also adopt identical structures in the solid state and in solution with two amides and four bidentate nitrate ions. With branched alkyl chain amides, the coordination structure of Pu(IV) was more difficult to establish unambiguously from EXAFS. Density functional theory (DFT) calculations were consequently performed on a series of structures with different coordination modes. Structural parameters and Debye-Waller factors derived from the DFT calculations were used to compute EXAFS spectra without using fitting parameters. By using this methodology, it was possible to show that the branched alkyl chain amides form partly outer-sphere complexes with protonated ligands hydrogen bonded to nitrate ions.

Columnar Liquid-Crystalline Dibenzopentacenodithiophenes by Photocyclization.

The twofold glyoxylic Perkin reaction of perylene-3,9-diglyoxylic acid with thiophene-diacetic acid followed by oxidative photocylization and reaction with α-branched primary alkylamines yields columnar liquid-crystalline diimides with two sulfur atoms in the condensed arene system. A broad temperature range of the hexagonal columnar mesophase is induced by racemic doubly branched alkyl chains. The HOMO and LUMO energy levels of these thiophene-derived diimides qualify them as electron donors with respect to perylene diimides.

Physicochemical properties of fatty acid based ionic liquids

In this work a series of fatty acid based ionic liquids has been synthesized and characterized. Densities and viscosities at different temperatures have been measured in the temperature range from (293.15 to 363.15)K. The thermal operating window and thermal phase behavior have been evaluated. The effects of a branched anion and a mono-unsaturated anion on the physicochemical properties have been explored. It has been observed that the density (T=298.15K) decreases with the following sequence: methyltrioctylammonium 4-ethyloctanoate>methyltrioctylammonium oleate≈tetrahexylammonium oleate>tetraoctylammonium oleate, with no detectable dependency of the thermal expansion coefficients on the total number of carbons in the ionic liquid. An almost linear correlation between the molar volumes and the total number of carbons of the alkanes together with the studied ionic liquids was found. The experimental viscosity data were correlated using the Vogel–Fulcher–Tammann (VFT) equation, where a maximum relative deviation of 1.4% was achieved. The ionic liquid with branched alkyl chains on the anion presents the highest viscosity, and methyltrioctylammonium oleate has the highest viscosity compared to the rest of the oleate based ionic liquids. The short and long-term stability were evaluated for all ionic liquids, their long-term decomposition temperatures were found to be significantly lower than their short-term decomposition temperatures. From the long-term thermal analysis was concluded that the highest temperature at which these ionic liquids can be kept is 363K. In addition, the thermal behavior, glass transition temperature, crystallization behavior and melting temperatures of the studied ionic liquids are presented.

Synthesis and properties of two surfactants containing polyoxypropylene block and short branched alkyl chain

Short branched alkyl polyoxypropylene sulfates, sodium isohexyl polyoxypropylene sulfate (i-HPS) and sodium isooctyl polyoxypropylene sulfate (i-OPS) were synthetized via propoxylation, sulfation, and neutralization three-step reactions, and characterized by FT-IR and 1H NMR. Their Krafft points were measured and the results were all below freezing point. Their critical micelle concentrations (cmc) and minimum surface tension (γcmc) determined by equilibrium surface tension were 54.74mmolL−1 and 32.12mNm−1 for i-HPS, 15.57mmolL−1 and 33.33mNm−1 for i-OPS, respectively. The measurement of dynamic surface tension indicated that both the equilibrium values of surface tension and the time required for reaching the equilibrium decreased with the increasing concentration of surfactant solutions. The spreading ability on paraffin film researched through dynamic contact angle revealed that the droplet of i-HPS solution presented a minimum contact angle of 58.9° at a concentration of 150mmolL−1, while the equilibrium contact angle of i-OPS droplet was 52.8° under the same condition. Their salt tolerance measurement showed that 1.0wt% i-HPS solution and 1.0wt% i-OPS solution could endure 183.1gL−1, 143.9gL−1 NaCl, 206.3gL−1, 198.4gL−1 MgCl2, and 229.7gL−1, 217.9gL−1 CaCl2, respectively.

“N-alkyl diketopyrrolopyrrole-based fluorophores for luminescent solar concentrators: Effect of the alkyl chain on dye efficiency”

We report on the preparation of luminescent solar concentrators (LSCs) made of poly(methyl methacrylate) (PMMA) thin films doped with six new diketopyrrolopyrrole (DPP) fluorophores obtained in good yields by using simple N-alkylation and direct CH arylation synthetic strategies. Spectroscopic investigations in solution and in PMMA thin films combined with photocurrent measurements revealed that the branched alkyl chains were efficient in preventing DPP segregation from the PMMA matrix thanks to their higher steric hindrance. The aromatic substituent was found to expand DPP conjugation but favoured DPP adverse aggregation, thus affecting fluorescence emission and photocurrents of PMMA films. The worthwhile combination of the appropriate alkyl chain and aromatic moieties assured to achieve optical efficiency of 6.8% that was comparable to that of PMMA LSCs of the state-of-the art (7.2%).