Effect Of Alkyl Side Chain Length Research Articles

The validity of high pressure IR for detecting the interactions between β-cyclodextrin and imidazolium based ionic liquids

The effects of alkyl side-chain length on the interactions between imidazolium ionic liquids (ILs) and β-cyclodextrin (β-CD) were studied at ambient pressure and up to 2.5GPa. No noticeable changes in the C-H band frequencies of 1-methyl-3-propylimidazolium hexafluorophosphate ([MPIM][PF6]) were observed upon β-CD addition under ambient pressure. Nevertheless, β-CD addition inhibited the formation of the [MPIM][PF6] aggregated structure under pressures of ≤0.7 GPa. As the pressure was raised to 1.1–2.5 GPa, [MPIM][PF6] aggregated and formed self-associated configurations. This pressure-induced dissociation was not detected in the 1-butyl-3-methylimidazolium hexafluorophosphate and β-CD mixture ([BMIM][PF6]-β-CD) due to the long side chain in the [BMIM] cation. This indicates that the alkyl side-chain length of the imidazolium ILs plays a non-negligible role in controlling the order and strength of IL-β-CD interactions. It is well known that the validity of infrared spectroscopy for detecting the inclusion complexation is questionable in the literature. However, this study demonstrates that the combination of high pressure and IR spectroscopy may provide a suitable way to monitor the IL-β-CD interactions.

Polyfluorene (PF) Single-Chain Conformation, β Conformation, and Its Stability and Chain Aggregation by Side-Chain Length Change in the Solution Dynamic Process

The effects of alkyl side-chain length with different carbon atom number, called poly(9,9di-hexlyfluorene) (PF6), poly(9,9-diheptylfluorene) (PF7), poly(9,9-dioctylfluorene) (PF8), poly(9,9-dinonylfluorene) (PF9), and poly(9,9-didecylfluorene) (PF10), on the polyfluorene (PF) single-chain conformation, β conformation, and its stability and chain aggregation in the solution dynamic process were systematically investigated by dynamic/static light scattering, UV–vis absorption spectra, photoluminescence spectra, and scanning electron microscopy. β conformation was the low-energy chain conformation, and its characteristic peak was at 437, 427, and 428 nm in the UV–vis spectrum of PF8, PF9, and PF10, respectively. It was interestingly found that the shape parameters (Rg/Rh) (i.e., ratio of radius of gyration (Rg) and hydrodynamic radius (Rh)) of PF single chains in toluene solution showed an odd–even property with the increase in side-chain length, which revealed that PF chains with even carbon atoms were more rigid than those with odd carbon atoms. The highest contents of β conformation were all ∼42% in PF8, PF9, and PF10 toluene/ethanol mixed solutions, but PF8 most easily formed the β conformation, PF9 followed, and PF10 was last. It was first found that the β-conformation formation and content were strongly connected to the chain packing density but not to aggregation size. High chain packing density was more advantageous to β-conformation formation; it had been well proved by static fractal dimension (df), reflecting the compactness of chain aggregation (i.e., chain packing density) and the chain self-similarity, and calculated by exponential law from SLS. Besides, it was also found that the β-conformation content could be stabilized at the maximum value range (42%) in the high ethanol content (80%) and independent of the side-chain length even after placing for 21 days, whereas in lower ethanol content (30 and 40%), the β-conformation content could also be stabilized in two different time stages. The conclusions are significant to understand deeply the solution dynamics process of film formation based on condensed matter physics of the conjugated polymer to control its condensed matter structure to achieve photoelectric devices with high carrier mobility, stability, and efficiency.

Molecular dynamics simulation of amino acid ionic liquids near a graphene electrode: effects of alkyl side-chain length.

Electric double layer (EDL) supercapacitors, using ionic liquid electrolytes, have been receiving a great deal of attention in response to the growing demand for energy storage systems. In the present study, the nanoscopic structure of amino acid ionic liquids (AAILs) as biodegradable electrolytes near a neutral graphene surface was studied by molecular dynamics (MD) simulation. In order to explore the influence of the anion type and structure, the effect of the alkyl side-chain length of amino acids on the EDL was investigated. The results for the AAILs, composed of 1-ethyl-3-methylimidazolium ([EMIM]) cations near alanine ([ALA]) and isoleucine ([ILE]) anions, were compared to a conventional electrolyte, [EMIM][PF6]. A lower mobility of AAIL compared to [EMIM][PF6], with diffusions as low as 10-11 m2 s-1, was observed. The structural results demonstrated a layered structure near the surface and most of the adsorbed imidazolium cation rings lay flat on the graphene surface. Both MD and quantum computations were performed to shed light on the charge behavior of AAIL electrolytes. As the current results demonstrate, an increase in the anion side-chain length leads to a decrease in both the number of adsorbed ions on the surface and the thickness of the first adsorbed layer. More impressively, it was observed that a low charge concentration in the EDL of AAILs is due to more side-side interactions. This remarkable feature could introduce AAILs as more efficient electrolyte materials than conventional [EMIM][PF6].

Effect of alkyl side-chain length on the photophysical, morphology and photoresponse properties of poly(3-alkylthiophene)

The effect of alkyl side-chain length on the photophysical, morphology and photoresponse properties of poly (3-alkylthiophene) (P3AT) has been investigated. Butyl, hexyl, octyl, decyl, and dodecyl side chains have been studied. In solution state, the average lifetime of poly (3-octylthiophene) (P3OT) is the shortest among P3AT solution owing to the strong intrachain interaction. The fluorescence lifetime of P3AT solution increases with the side-chain length increasing. A similar trend occurs in the P3AT films. This phenomenon illustrates conformation ‘memory’ property evolving from solution state to solid film. The four lifetimes represent different photophysical processes and have been systematically analyzed. The photodetector based on P3DDT is a suitable candidate for practical application owing to the fast, reversible photoresponse and photostability. The high performance of P3DDT-based photodetector is correlated to the optimized morphology and strong interchain interaction which promotes the exciton delocalization.

Side-Chain Influence on the Mass Density and Refractive Index of Polyfluorenes and Star-Shaped Oligofluorene Truxenes

The density of organic semiconductor films is an important quantity because it is related to intermolecular spacing which in turn determines the electronic and photophysical properties. We report thin film density and refractive index measurements of polyfluorenes and star-shaped oligofluorene truxene molecules. An ellipsometer and a procedure using a spectrophotometer were used to determine film thickness and mass of spin-coated films, respectively. We present a study of the effect of alkyl side-chain length on the volumetric mass density and refractive index of the materials studied. The density measured for poly(9,9-di-n-octylfluorene) (PF8) was 0.88 ± 0.04 g/cm3 and decreased with longer alkyl side chains. For the truxene molecule with butyl side chains (T3 butyl), we measured a density of 0.90 ± 0.04 g/cm3, which also decreased with increasing side-chain length.

The effects of alkyl side-chain length and shape of polyfluorenes on the photoluminescence spectra and the fluorescence lifetimes of polyfluorene blends with poly( n-vinylcarbazole)

The effects of side-chain length and shape at C-9 position of polyfluorenes on the photoluminescence spectra and the fluorescence lifetimes are investigated for blue light-emitting poly( n-vinylcarbazole)/polyfluorene blends. As the side-chain length of alkyl-substituted polyfluorenes and of bulky cyclohexyl-substituted polyfluorenes increases, the fluorescence lifetime of the blends increase from 1 to 10 ns and the portion of PVK component contributing to the fluorescence lifetime of the blends increases. However, PL intensity of the blend decreases. This provides the side-chain length and shape of polyfluorene could affect the efficiency of energy transfer.

Effect of alkyl side-chain length and solvent on the luminescent characteristics of poly(3- n-alkylthiophene)

In poly(3- n-alkylthiophene) (P3AT), the length of alkyl side chain as well as the solvent used for film casting affected the conformation and eventually the luminescent characteristics of the polymers. When the length of alkyl side chain was shorter than 12 carbon atoms, the electronic absorption and PL spectra of P3AT film showed red shift as the length of the alkyl side chain increased. This is because, when the length of the alkyl side chain is not too long, solvation is promoted with increase in the length of the alkyl side chain, leading to expanded chain structures with longer π-conjugation lengths. Conversely, when the length of the alkyl side chain was longer than 12 carbon atoms, the electronic absorption and PL spectra of P3AT film showed blue shift as the length of the alkyl side chain increased. This is because, when the length of the alkyl side chain is too long, the steric hindrance becomes predominant leading to highly distorted chain conformation with shorter π-conjugation lengths. The PL intensity of the film cast from THF was higher by an order of magnitude than that of the film cast from chloroform, toluene, or p-xylene. In the P3AT films cast from a poor solvent such as THF, the polymer chains are highly distorted leading to high PL intensity due to exciton localization. In the EL spectra of P3AT films cast from various solvents, λ max shifted as much as 140 nm depending upon the solvent characteristics. This result demonstrates that the color of EL can be varied from blue to orange simply by casting the same polymer from a different solvent.

Construction of hairy-rod coordination polymers with lamellar structure by self-assembling of hexakis(4-pyridylmethoxy)cyclotriphosphazene and silver alkylsulfonates

The supramolecular self-assembly of hexakis(4-pyridylmethoxy)cyclotriphosphazene (PyPN) and silver alkylsulfonates AgSO 3C n H 2 n+1 ( n=12, 14, 16, 18) gave a new type of hairy-rod coordination polymer. Elemental analysis, FT-IR, differential scanning calorimetry and X-ray diffraction techniques indicated that the coordination polymers with an alternating sequence of one PyPN and three Ag + ions bearing alkylsulfonate anions as side chains are formed to give a hairy-rod structure. The hairy-rod polymers with alkyl side-chains of AgC 14 ( n=14), AgC 16 ( n=16) and AgC 18 ( n=18) are organized in lamellar structures, where the alkyl chains tilted with respect to the polymer backbone by ca. 40° are interdigitated with each other. On the other hand, the coordination polymer with an alkyl side-chain of AgC 12 ( n=12) did not distinctly form the lamellar structure due to the relatively short alkyl chains. The effects of alkyl side-chain length on the formation of lamellar structure of the coordination polymers are described.

Alkylfurans: effects of alkyl side-chain length on insecticidal activity.

The insecticidal activity of five alkylfurans against the generalist insect herbivore beet armyworm, Spodoptera exigua, was examined. Two naturally occurring compounds, the avocadofurans 2-(pentadecyl)furan (1) and 2-(heptadecyl)furan (2), previously isolated from specialized avocado idioblast oil cells, and three homologues, 2-(tetradecyl)furan (3), 2-(hexadecyl)furan (4), and 2-(octadecyl)furan (5), were synthesized. Bioassays of alkylfurans 1-5 using a 9-day diet-incorporation initiated with neonates showed that all alkylfurans tested significantly increased S. exigua larval mortality and reduced larval weights, with maximal biological activity detected among the naturally occurring alkylfurans 1 and 2.