Alkyl Chain Length (alkyl + chain_length)

Distribution by Scientific Domains

Kinds of Alkyl Chain Length

  • different alkyl chain length

  • Selected Abstracts

    Smectic phases of liquid crystals based on dinuclear palladium(II) complexes with carboxylato bridge

    V. Crcu
    Abstract In this paper we present the preparation and the investigation of the liquid crystal properties of a series of dinuclear carboxylato bridge Pd(II) complexes bearing six alkoxy peripheral chains in the molecule. Their structures were assigned based on elemental analysis, IR and 1H NMR spectroscopy whereas the thermal behaviour was investigated by polarizing optical microscopy and differential scanning calorimetry. The monotropic smectic A phase displayed by these materials was identified by miscibility studies with a previously reported mesogen. It was found that the transition temperatures and the SmA mesophase stability depend on the alkyl chain length of the carboxylato bridge. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Polymeric alkenoxy amino acid surfactants: I. Highly selective class of molecular micelles for chiral separation of ,-blockers

    ELECTROPHORESIS, Issue 15 2003
    Syed A. A. Rizvi
    Abstract Two amino acid-based alkenoxy micelle polymers were synthesized for this study. These include polysodium N -undecenoxy carbonyl- L -leucinate (poly- L -SUCL) and polysodium N -undecenoxy carbonyl- L -isoleucinate (poly- L -SUCIL). The polymerization time and concentration of the synthesized micelle polymers were optimized by 1H-nuclear magnetic resonance (NMR) and capillary electrophoresis (CE) experiments. Detailed physicochemical properties (1H NMR, critical micelle concentration (CMC), optical rotation, partial specific volume, aggregation number, and polarity) were determined, and these molecular micelles were introduced as a pseudostationary phase in micellar electrokinetic chromatography to study the molecular recognition and to develop a method for simultaneous separation of eight chiral ,-blockers. It is found that poly- L -SUCL gives overall better chiral resolution and wider chiral window than poly- L -SUCIL. After optimizing the type of micelle polymer, injection size and temperature, simultaneous separation and enantioseparation of eight ,-blockers were achieved in less than 35 min. A comparison with the amide-type surfactants of the same polar head group and alkyl chain length showed that carbamate-type surfactants always work better than the corresponding amide-type surfactant. [source]

    Effect of ethoxylate number and alkyl chain length on the pathway and kinetics of linear alcohol ethoxylate biodegradation in activated sludge

    Nina R. Itrich
    Abstract Batch activated-sludge die-away studies were conducted with various pure homologs to determine the effect of ethoxylate number and alkyl chain length on the kinetics of primary and ultimate biodegradation of linear alcohol ethoxylates. The 14C-(ethoxylate) homologs C14E1, C14E3, C14E6, and C14E9 were used to investigate the effect of ethoxylate number, and 14C-(ethoxylate) homologs C12E6, C14E6, and C16E6 were used to examine the effect of chain length. Activated sludge was dosed with a trace concentration (0.2 ,M) of each homolog, and the disappearance of parent, formation of metabolites, production of 14CO2, and uptake into solids were monitored with time. Ethoxylate number had little effect on the first-order decay rates for primary biodegradation, which ranged from 61 to 78 h,1. However, alkyl chain length had a larger effect, with the C16 chain-length homolog exhibiting a slower rate of parent decay (18 h,1) compared to its corresponding C12 and C14 homologs (61,69 h,1). Ethoxylate number affected the mechanism of biodegradation, with fission of the central ether bond to yield the corresponding fatty alcohol and (poly)ethylene glycol group increasing in dominance with increasing ethoxylate number. Based upon the measured rates of primary biodegradation, removal of parent during activated-sludge treatment was predicted to range between 99.7 and 99.8% for all homologs except C16E6, which had a predicted removal of 98.9%. Based upon the measured rates of ultimate biodegradation, removal of ethoxylate-containing metabolites was predicted to exceed 83% for all homologs. These predictions corresponded closely with previously published removal measurements in laboratory continuous activated-sludge systems and actual treatment plants. [source]

    Solubilities and surface activities of phthalates investigated by surface tension measurements

    Marianne Thomsen
    Abstract Aueous solutions of DEP (di-ethyl), DnBP (di- n -butyl), DnH(6)P (di- n -hexyl), and DEHP (di-[2-ethyl-hexyl])phthalates have been investigated by use of surface tension measurements at temperatures between 10 and 35C. A tensiometric approach allows for the determination of unimeric solubilities and ,G, which is the standard Gibbs free energy change, for the dissolution of phthalates in water. The unimeric solubility of the phthalates increase with decreasing temperature. The ,G shows a linear increase with increasing phthalate alkyl chain length. The contribution of enthalpy (,H) and entropy (,S) to ,G were calculated from the temperature-dependent solubilities. The contributions of both ,H and ,S are negative and increase in magnitude with increasing alkyl chain length, suggesting hydrophobic interactions between phthalates and water. The ability of different phthalates to lower the surface tension decreases with increasing alkyl chain length, whereas the relative affinity for adsorption in the air-water interface increases drastically for long-chain phthalates. Despite the low surface activity of phthalates compared with that of common surfactants, they show significant affinity for adsorption in air-water interfaces of natural surface waters. This property, combined with their low solubilities, may affect the fate of these compounds within the natural environment, because they form emulsions above unimeric saturation in aqueous media. [source]

    Structure,activity relationships for acute and chronic toxicity of alcohol ether sulfates

    Scott D. Dyer
    Abstract Acoholethersulfates(AES)areanionicsurfactantscommonlyusedinconsumerproducts. Commercial AES alkyl chain lengths range from C12 to C18, with ethoxylate (EO) units ranging from 1 to 5. Alkyl sulfate is a special case of AES with no EO units. Acute and chronic toxicity tests using Ceriodaphnia dubia via a novel flowthrough method were conducted with 18 AES compounds to derive SARs for effects assessment. In general, acute toxicity (48-h LC50) increased with increased alkyl carbon chain length and decreased with increased numbers of EO units. Parabolic structure,chronic (7-d) toxicity relationships were observed for endpoints such as the no-observed-effect concentration, lowest-observed-effect concentration, maximum acceptable toxicant concentration, EC20, and EC50. A linear relationship of the fractional negative-charged surface area (FNSA-3) with acute toxicity was also determined. FNSA-3 refers primarily to the polar head group of AES and secondarily to the alkyl chain. Seventy percent of the variance in the chronic data was addressed with a quadratic equation relating toxicity to alkyl chain length and EO units. Alternatively, the molecular descriptors FNSA-3 and S3P (3,p, which is the simple, third-order path index) were also found to address most of the data nonlinearity. A chronic test conducted with a mixture of four AES components indicated additivity, leading to the support of the performance of an effects assessment of AES as a mixture. [source]

    Biomimetic Self-Assembly of Tetrapeptides into Fibrillar Networks and Organogels

    Sajid Iqbal
    Abstract The self-assembly features of a family of tetrapeptides with a silk-inspired structure are presented. An exhaustive study of the influence of the terminal alkyl chain length in this process is undertaken. Scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD), FTIR spectroscopy, and circular dichroism were used for structural analysis. These compounds, as in the natural model, self-assemble into antiparallel ,-sheet structures that further organize to form fibrillar aggregates. Furthermore, some of them arecapable of forming a crowded network that entraps thesolvent leading to physical gels with different microscopic morphologies. A model for the assembly process is proposed.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Effect of Carbon Chain Length in the Substituent of PCBM-like Molecules on Their Photovoltaic Properties

    Guangjin Zhao
    Abstract A series of [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM)-like fullerene derivatives with the butyl chain in PCBM changing from 3 to 7 carbon atoms, respectively (F1,F5), are designed and synthesized to investigate the relationship between photovoltaic properties and the molecular structure of fullerene derivative acceptors. F2 with a butyl chain is PCBM itself for comparison. Electrochemical, optical, electron mobility, morphology, and photovoltaic properties of the molecules are characterized, and the effect of the alkyl chain length on their properties is investigated. Although there is little difference in the absorption spectra and LUMO energy levels of F1,F5, an interesting effect of the alkyl chain length on the photovoltaic properties is observed. For the polymer solar cells (PSCs) based on P3HT as donor and F1,F5, respectively, as acceptors, the photovoltaic behavior of the P3HT/F1 and P3HT/F4 systems are similar to or a little better than that of the P3HT/PCBM device with power conversion efficiencies (PCEs) above 3.5%, while the performances of P3HT/F3 and P3HT/F5-based solar cells are poorer, with PCE values below 3.0%. The phenomenon is explained by the effect of the alkyl chain length on the absorption spectra, fluorescence quenching degree, electron mobility, and morphology of the P3HT/F1,F5 (1:1, w/w) blend films. [source]

    Alkyl-Chain-Length-Independent Hole Mobility via Morphological Control with Poly(3-alkylthiophene) Nanofibers

    Wibren D. Oosterbaan
    Abstract The field-effect transistor (FET) and diode characteristics of poly(3-alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n -alkyl-side-chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV,vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K -edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl-chain-length-dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side-chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. [source]

    Effect of Alkyl Side-Chain Length on Photovoltaic Properties of Poly(3-alkylthiophene)/PCBM Bulk Heterojunctions

    Abay Gadisa
    Abstract The morphological, bipolar charge-carrier transport, and photovoltaic characteristics of poly(3-alkylthiophene) (P3AT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends are studied as a function of alkyl side-chain length m, where m equals the number of alkyl carbon atoms. The P3ATs studied are poly(3-butylthiophene) (P3BT, m,=,4), poly(3-pentylthiophene) (P3PT, m,=,5), and poly(3-hexylthiophene) (P3HT, m,=,6). Solar cells with these blends deliver similar order of photo-current yield (exceeding 10,mA cm,2) irrespective of side-chain length. Power conversion efficiencies of 3.2, 4.3, and 4.6% are within reach using solar cells with active layers of P3BT:PCBM (1:0.8), P3PT:PCBM (1:1), and P3HT:PCBM (1:1), respectively. A difference in fill factor values is found to be the main source of efficiency difference. Morphological studies reveal an increase in the degree of phase separation with increasing alkyl chain length. Moreover, while P3PT:PCBM and P3HT:PCBM films have similar hole mobility, measured by hole-only diodes, the hole mobility in P3BT:PCBM lowers by nearly a factor of four. Bipolar measurements made by field-effect transistor showed a decrease in the hole mobility and an increase in the electron mobility with increasing alkyl chain length. Balanced charge transport is only achieved in the P3HT:PCBM blend. This, together with better processing properties, explains the superior properties of P3HT as a solar cell material. P3PT is proved to be a potentially competitive material. The optoelectronic and charge transport properties observed in the different P3AT:PCBM bulk heterojunction (BHJ) blends provide useful information for understanding the physics of BHJ films and the working principles of the corresponding solar cells. [source]

    1D and 3D Ionic Liquid,Aluminum Hydroxide Hybrids Prepared via an Ionothermal Process,

    S. Park
    Abstract Room-temperature ionic liquids (RTILs) are used as hierarchically multifunctional components by employing them not only as templates and co-solvents for fabricating nanostructured materials but also proton conductors for electrochemical devices. RTIL/aluminum hydroxide (RTIL,Al) hybrids containing various nanometer-sized shapes, including 1D nanorods with hexagonal tips, straight and curved nanofibers, nanofibers embedded in a porous network, and 3D octahedral-, polyhedral-, and angular spherical shapes are synthesized via a one-pot ionothermal process. The structures or shapes of the RTIL,Al hybrids are related to the anionic moieties, alkyl chain length of the RTILs, and the humidity during fabrication. In particular, the introduction of water molecules into the interface led to 3D isotropic growth of the hybrids by influencing intermolecular interactions between the RTILs and the building blocks. The shapes of the nanohybrids fabricated from RTILs containing short alkyl chains were dependent on the types of anions and on the level of humidity. These results indicate that the cooperative interactions between RTILs and aluminum hydroxides induces emerging shape-controlled hybrids. The shape-controlled nanohybrids show enhanced electrochemical properties compared to those of a conventional hybrid prepared by mixing RTILs and aluminum hydroxides, exhibiting tenfold or higher proton conductivity under anhydrous condition and thermal stability as a result of the continuous proton conduction channel and the one-pot-assembled nanoconfinement. This method is expected to be a useful technique for controlling the diverse shapes of nanometer-sized crystalline inorganic materials for a variety of applications, such as fuel cells, solar cells, rechargeable batteries, and biosensors. [source]

    Kinetic study of the reaction of dimethyl carbonate with trialkylamines

    Duane E. Weisshaar
    Quaternary ammonium compounds are produced worldwide in hundreds of millions of pound volume annually for a plethora of end-uses from fabric-care formulations to asphalt emulsifiers, typically from nongreen alkylating reagents. The kinetics of a reaction employing dimethyl carbonate (DMC) as a green alkylating agent was investigated using three trialkylamines (tributylamine, trihexylamine, and trioctylamine) at several temperatures. Arrhenius and Eyring analysis of the data showed that values of Ea (79 kJ/mol), ,H, (75 kJ/mol), and ,S, (220 J/(mol K)) were the same for all three amine reactants, consistent with a report that Ea is independent of alkyl chain length when the chain length is greater than three carbons. Although rates are significantly slower with DMC than with other alkylating reagents, the resulting methyl carbonate anion has advantages for clean anion metathesis, which is important for some applications, especially those involving ionic liquids. 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 221,225, 2010 [source]

    Controlled release of argatroban from PLA film,Effect of hydroxylesters as additives on enhancement of drug release

    Akira Mochizuki
    Abstract The aim of this study was to develop a drug eluting stent that prevents vein restenosis. For this, we selected argatroban as the study drug and poly(lactic acid) (PLA) as the matrix. To enhance the release of argatroban from PLA film, the addition of hydroxylesters (additives) was investigated. The additives investigated were diethyl tartrate (DET), diethyl malate (DEM), and triethyl citrate (TEC). Marked enhancement of drug release was observed in DET-added film, while TEC- or DEM-added film showed little enhancement. To clarify the effect of DET, the release profile based on the contents of the drug and DET in the film and the effect of alkyl chain length of tartrate were studied. Tartrates used were dimethyl, di- i -propyl, and di- n -butyl esters (DMT, DiPT, and DnBT, respectively), and the enhancement order was DMT , DET , DiPT , DBT , PLA alone. The reasons for enhancement were discussed from the viewpoint of drug release behavior, degradation of PLA, water uptake within the film, and SEM observations. It was concluded that enhancement of drug release was due to large amounts of water uptake within the film which resulted in the formation of open pores at its surface. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Synthesis and comparative physicochemical investigation of partly aromatic cardo copolyesters

    N. B. Joshi
    Abstract Copolyesters were synthesized through the condensation of 0.0025 mol of 1,1,-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 0.0025 mol of ethylene glycol/propylene glycol/1,4-butanediol/1,6-hexane diol, and 0.005 mol of terephthaloyl chloride with water/chloroform (4:1 v/v) as an interphase, 0.0125 mol of sodium hydroxide as an acid acceptor, and 50 mg of cetyl trimethyl ammonium bromide as an emulsifier. The reaction time and temperature were 2 h and 0C, respectively. The yields of the copolyesters were 81,96%. The structures of the copolyesters were supported by Fourier transform infrared and 1H-NMR spectral data and were characterized with the solution viscosity and density by a floatation method (1.1011,1.2697 g/cm3). Both the intrinsic viscosity and density of the copolyesters decreased with the nature and alkyl chain length of the diol. The copolyesters possessed fairly good hydrolytic stability against water and 10% solutions of acids, alkalis, and salts at room temperature. The copolyesters possessed moderate-to-good tensile strength (11,37.5 MPa), good-to-excellent electric strength (19,45.6 kV/mm), excellent volume resistivity (3.8 1015 to 2.56 1017 , cm), and high glass-transition temperatures (148,195C) and were thermally stable up to about 408,427C in a nitrogen atmosphere; they followed single-step degradation kinetics involving 38,58% weight losses and 34,59% residues. The copolyesters followed 2.6,2.9-order degradation kinetics. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Antimicrobial finishing of wool fabrics with quaternary aminopyridinium salts

    Tao Zhao
    Abstract Quaternary aminopyridinium salts were employed in antimicrobial finishing wool fabrics. The effects of alkyl chain length in the salts, pH conditions of finishing baths, finishing time and temperature, and salt concentrations were investigated. The incorporated quaternary aminopyridinium salt molecules on wool were characterized by FTIR. The quaternary ammonium salt could form ionic interactions with anionic groups on wool, which contribute to the durable antimicrobial functions. All the finished wool fabrics exhibited antimicrobial efficacy against Escherichia coli. The washing durability of antimicrobial functions on the finished wool fabrics was also studied. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 482,486, 2007 [source]

    Oestrogenic activity of isobutylparaben in vitro and in vivo

    P. D. Darbre
    Abstract The alkyl esters of p -hydroxybenzoic acid (parabens) are used widely as preservatives in foods, pharmaceuticals and cosmetics to which the human population is exposed. Recent studies have reported that methylparaben, ethylparaben, n -propylparaben and n -butylparaben all possess oestrogenic activity in several in vitro assays and in animal models in vivo. This study reports on the oestrogenic activity of isobutylparaben in a panel of assays in vitro and in vivo. Isobutylparaben was able to displace [3H]oestradiol from cytosolic oestrogen receptor , of MCF7 human breast cancer cells by 81% at 100 000-fold molar excess. Using a clonal line of MCF7 cells containing a stably transfected oestrogen-responsive ERE-CAT reporter gene, CAT gene expression could be increased by isobutylparaben such that the magnitude of the response was the same at 10,5 M isobutylparaben as with 10,8 M 17,-oestradiol. Isobutylparaben could also increase expression of the endogenous oestrogen-responsive pS2 gene in MCF7 cells and maximal expression at 10,5 M isobutylparaben could be inhibited with the anti-oestrogen ICI 182 780. The proliferation of two oestrogen-dependent human breast cancer cell lines MCF7 and ZR-75-1 could be increased with isobutylparaben such that at concentrations of 10,5 M the proliferation response was of the same magnitude as with 10,8 M 17,-oestradiol. Evidence for oestrogen receptor mediation of proliferation effects was provided by the inability of isobutylparaben to influence the growth of oestrogen-unresponsive MDA-MB-231 human breast cancer cells and by the ability of the anti-oestrogen ICI 182 780 to inhibit the isobutylparaben effects on MCF7 cell growth. The proliferation response to 10,10 M 17,-oestradiol was not antagonized with isobutylparaben at any concentration from 10,9 M to 10,4 M in either MCF7 or ZR-75-1 cells. Finally, subcutaneous administration of isobutylparaben was able to increase the uterine weight in the immature mouse after three daily doses of 1.2 or 12.0 mg per mouse. Previous work using linear-alkyl-chain parabens has shown that oestrogenic activity increases with alkyl chain length from methylparaben to n -butylparaben. The results here show that branching of the alkyl chain to isobutylparaben increases oestrogenic activity beyond that of the equivalent length linear alkyl chain in n -butylparaben. Copyright 2002 John Wiley & Sons, Ltd. [source]

    Synthesis of new heterocycles containing more than one 1,2,3-thia or selenadiazole rings

    Mousa Al-Smadi
    The diketones 2a-d with different alkyl chain length are used for the synthesis of di-1,2,3-thia or selenadiazole derivatives 4a-d and 5a-d. The diketones 2a-d where prepared by a unique method through the reaction between the corresponding dibromoalkanes 1a-d and ethyl acetoacetate, which are transformed into the corresponding semicarbazone derivatives 3a-d. The di-1,2,3-thia or selenadiazole derivatives 4a-d and 5a-d were prepared from the semicarbazones derivatives 3a-d on oxidative cyclization with thionyl chloride and selenium dioxide respectively in high yield. [source]

    Collision-induced dissociation of sulfur-containing imidazolium ionic liquids

    Alain Lesimple
    Abstract A number of 1,2-dimethylimidazole ionic liquids substituted on NII with alkyl chains of varying lengths terminated with sulfur-containing groups were investigated by electrospray high-resolution tandem Fourier-transform mass spectrometry. Fragmentation pathways are strongly dependent on the oxidation state of the sulfur and the alkyl chain length. The dissociations detected are rationalized by deuterium labeling, comparisons between homologous compounds and accurate mass data. Several homolytic processes are reported, leading to distonic ions and loss of hydrogen, methyl and other free radicals. Copyright 2007 John Wiley & Sons, Ltd. [source]

    Global phase behavior of imidazolium ionic liquids and compressed 1,1,1,2-tetrafluoroethane (R-134a)

    AICHE JOURNAL, Issue 2 2009
    Wei Ren
    Abstract Novel processes involving ionic liquids with refrigerant gases have recently been developed. Here, the complete global phase behavior has been measured for the refrigerant gas, 1,1,1,2-tetrafluoroethane (R-134a) and 1- n -alkyl-3-methyl-imidazolium ionic liquids with the anions hexafluorophosphate [PF6], tetrafluoroborate [BF4] and bis(trifluoromethylsulfonyl)imide [Tf2N] from ,0C to 105C and to 33 MPa. All of the systems studied were Type V from the classification scheme of Scott-van Konynenburg with regions of vapor-liquid equilibrium, miscible/critical regions, vapor-liquid-liquid equilibrium, and upper and lower critical endpoints (UCEP and LCEP). The effect of the alkyl chain length has been investigated, for ethyl-([EMIm]), n -butyl-([BMIm]), and n -hexyl-([HMIm]). With increasing chain length, the temperature of the lower critical end points increases and pressure at the mixture critical points decrease. With a common cation, the temperature of the LCEP increased and the mixture critical point pressures decreased in the order of [BF4], [PF6], and [Tf2N]. 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Influences of alkyl group chain length and polar head group on chemical skin permeation enhancement

    Kevin S. Warner
    Abstract Previous investigations in our laboratory on the influence of the n -alkanols and the 1-alkyl-2-pyrrolidones as skin permeation enhancers for steroid molecules as permeants demonstrated that the enhancer potencies (based on aqueous concentration values) of these two homologous series were the same when compared at the same alkyl chain length; that is, the contribution of the hydroxyl group and that of the pyrrolidone group to enhancer potency were the same. The purpose of the present study was to further investigate what was believed to be a somewhat surprising finding, and two additional homologous series, the 1,2-alkanediols and N,N -dimethylalkanamides, were selected for study as enhancers. Corticosterone (CS) flux enhancement along the lipoidal pathway of hairless mouse skin stratum corneum was determined with 1,2-hexane-, 1,2-octane-, and 1,2-decanediol and with N,N -dimethylhexanamide, N,N - dimethylheptanamide, N,N -dimethyloctanamide, and N,N -dimethylnonanamide as enhancers. The enhancement factor (E) for the lipoidal pathway was calculated from the CS permeability coefficient and the CS solubility data over a 4 to 100 range of E values. Comparisons of the enhancer potencies of all four homologous series revealed that the enhancer potencies of all were very nearly the same when compared at equal alkyl group chain length. Moreover, the contribution of each of the polar head groups toward the enhancer potency was essentially constant, independent of the alkyl group chain length. It was reasoned that this outcome was either the result of the random selection of four polar head groups making the same contribution to enhancer potency or the result of these particular polar head groups not contributing to enhancer potency. To test the hypothesis that the former was more likely than the latter and that a suitable semipolar organic phase may mimic the microenvironment of the polar head group at the site of enhancer action, n -octanol,phosphate buffered saline (PBS) and n -hexane,PBS partition coefficients were determined for all the enhancers. The n -octanol,PBS partition coefficients for the enhancers, but not the n -hexane,PBS partition coefficients, were very nearly the same when compared at equal alkyl group chain lengths; this result supports the hypothesis that each of the four polar head groups likely contributes the same toward the enhancer potency and locates in the semipolar region of the hairless mouse skin stratum corneum lipid bilayers, which is well-approximated by water-saturated n -octanol. 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1143,1153, 2001 [source]

    Bile acid sequestrants based on cationic dextran hydrogel microspheres.


    Abstract Cationic dextran hydrogel microspheres with pendant quaternary ammonium groups having alkyl substituents (C2,C12) at quaternary nitrogen were synthesized. The in vitro sorption of sodium salts of four bile acids (glycocholic, cholic, taurocholic, and deoxycholic acids) with these hydrogels was studied as a function of substituent alkyl chain length and bile acid hydrophobicity. Sorption experiments were performed in phosphate buffer solutions (pH 7.4) containing one bile salt (individual sorption) or mixtures of several bile salts (competitive sorption). Parameters for individual sorption were calculated taking into consideration the stoichiometric and cooperative binding of bile salts to oppositely charged polymer hydrogels. The results show that the increase in the length of the alkyl chain of the substituent leads to an increase in both ionization constant K0 and overall stability constant of binding K, but decreases the cooperativity parameter u. The competitive sorption studies indicate that the hydrogels display a good affinity for both dihydroxylic and trihydroxylic bile salts. The molar ratio of maximum amounts bound for the two types of bile acid is 2 to 1, which is much lower than those reported for other cationic polymers recommended as bile acid sequestrants. The binding constants for the sorption of bile salts by some dextran hydrogels are 20,30 times higher than those obtained for cholestyramine under similar sorption conditions. 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:681,689, 2001 [source]

    Functionalized surfactant mediated reactions of carboxylate, phosphate and sulphonate esters

    Shuchi Tiwari
    Abstract Nucleophilic reactivity of some functionalized surfactants, i.e. quaternary pyridinium aldoximes towards the hydrolysis of p -nitrophenyl acetate (PNPA), p -nitrophenyl benzoate (PNPB), p -nitrophenyldiphenyl phosphate (PNPDPP) and p -nitrophenyl p -toluene sulphonate (PNPTS) has been studied at pH 7.1 and 27,C. Addition of functionalized surfactant to reaction medium causes progressive increase in the rate of hydrolysis and reaches a maximum and then decreases due to further addition of surfactant. An increase in the alkyl chain length of functionalized surfactants resulted in an increase in the first-order rate constant. The apparent pKa and CMC of functionalized surfactants have also been determined by spectrophotometric and conductometric methods, respectively. Copyright 2009 John Wiley & Sons, Ltd. [source]

    Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and short-chain alcohols

    Chorng-Shyan Chern
    Abstract Styrene microemulsion polymerizations with different short-chain alcohols [n -CiH2i+1OH (CiOH), where i = 4, 5, or 6] as the cosurfactant were investigated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the surfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was obtained from the polymerizations at temperatures of 50,70 C. The polymerization kinetics were not very sensitive to the alkyl chain length of alcohols compared with the temperature effect. The maximal polymerization rate in decreasing order was C6OH > C4OH > C5OH. This was related to the differences in the water solubility of CiOH and the structure of the oil,water interface. The feasibility of using a water-insoluble dye to study the particle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (CiOH), the SPS concentration, and the initiator type (oil-soluble 2,2,-azobisisobutyronitrile versus water-soluble SPS). 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3199,3210, 2001 [source]

    Ionic liquids as mobile phase additives for high-performance liquid chromatography separation of phenoxy acid herbicides and phenols

    Xialin Hu
    Abstract In this present study, 1-butyl-3-methylimidazolium chloride ([C4MIM]Cl), 1-octyl-3-methylimidazolium chloride ([C8MIM]Cl), and 1-decyl-3-methylimidazolium chloride ([C10MIM]Cl) were adopted as mobile phase additives in the high performance liquid chromatography (HPLC) to simultaneously separate phenoxy acid herbicides and phenols at neutral pH. It was found that by using 20,mM of [C4MIM]Cl, baseline separation and good chromatograms for all the acid compounds were obtained on a normal reversed-phase C18 column. The retention time of the target acid compounds shortened with the increase of the alkyl chain length and the concentrations of ionic liquids, probably due to the delocalization of the positive charge on the imidazolium cation, the repulsion between chlorine ions of ionic liquids and the acid compounds, as well as the stereo-hindrance effect. The mechanism with ionic liquids as mobile additives for the separation of acid compounds was discussed. [source]

    Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenes

    Tarik Eren
    Abstract In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC50) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 g,,mL,1 and a HC50 greater than 1,650 g,,mL,1, while those with six or more carbons had lower MICs,,,12.5 g,,mL,1 and HC50,,,250 g,,mL,1. Using MSI-78, the potent Magainin derivative which has an MIC,=,12.0 g,,mL,1 and HC50,=,120 g,,mL,1, as a comparison, the polymers with alkyl substituents ,C4 (four carbons) were not very potent, but did show selectivity values greater than or equal to MSI-78. In contrast, those with alkyl substituents ,C6 were as potent, or more potent, than MSI-78 and in three specific cases demonstrated selectivity values similar to, or better than, MSI-78. To understand if these polymers were membrane active, polymer induced lipid membrane disruption activities were evaluated by dye leakage experiments. Lipid composition and polymer hydrophobicity were found to be important factors for dye release. [source]

    Conductive Composites of Polyurethane Resins and Ionic Liquids

    Belinda Berns
    Abstract Composites of PUR and IL were prepared and specific conductivities and Shore A hardness were determined. IL were based on 1-alkyl-3-methylimidazolium salts with counterions BF, PF, triflate, or ethylsulfate. Presence of IL increased the conductivity by five orders of magnitude. Variation of alkyl chain length and nature of counterions only had little effect on the conductivity. Presence of IL had a plasticizing effect, which was most pronounced for the IL with dodecyl groups and PF as counterion. In broadband dielectric measurements, the complex conductivity showed a characteristic dispersion that is caused by the interplay between (hopping) transport of charge carriers and electrode polarization. [source]

    Rheology control by modulating hydrophobic and inclusive associations of side-groups in poly (acrylic acid)

    Jie Wang
    Abstract In this article we demonstrated that the viscosities of modified poly (acrylic acid) (PAA) solutions were tunable by modulating the hydrophobic and inclusion association between alkyl groups and ,-cyclodextrin (,-CD) groups grafted to PAA. The viscosity can be controlled by changing the host,guest molar ratio, alkyl chain length, polymer concentration, salt concentration, pH value, temperature, or addition of native ,-CD. A viscosity maximum for inclusive polymer networks constructed by mixing hydrophobically modified PAA (HMPAA) and ,-CD,modified PAA (,-CDPAA) appeared at the alkyl : ,-CD molar ratio of 1:1, which implies the inclusion association between HM and ,-CD grafts is binary. Longer side chain length or higher polymer concentration led to higher viscosity for aqueous HMPAA solution with only hydrophobic association or its mixture with ,-CDPAA with inclusion association. Monotonically increasing the ionic strength or pH value resulted in a viscosity maximum due to the competition between electrostatic repulsion and hydrophobic or inclusive association. The hydrophobic interactions of alkyl groups could be masked by native ,-CD, and the networks of HMPAA and ,-CDPAA mixture deconstructed upon addition of native ,-CD molecules. The storage modulus and loss modulus of hydrophobic HMPAA and inclusive HMPAA + ,-CDPAA solutions obey time,temperature superposition. The horizontal and vertical temperature shift factors obeyed a simple-exponential Arrhenius relationship, where the activation energies for hydrophobic association system were found to be 3.4 and , 12.1 kJ/mol, and for inclusive association system 53.9 and , 2.9 kJ/mol, respectively. Copyright 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Effects of tetraalkylammonium compounds with different affinities for organic cation transporters on the pharmacokinetics of metformin

    Min-Koo Choi
    Abstract The study sought to investigate the effects of tetraalkylammonium (TAA), inhibitors of the organic cation transporters (OCTs) with different affinities, on the pharmacokinetics of metformin. The inhibitory potentials of TAAs on the uptake of metformin were evaluated by determining IC50 values in MDCK cells over-expressing OCTs and, to assess in vivo drug interactions, metformin and TAAs were coadministered to rats. Uptake of metformin was facilitated by over-expression of hOCT1 and hOCT2 and showed saturable processes, indicating that metformin is a substrate of hOCT1 and hOCT2. The IC50 values of TAAs for hOCT2 were lower than hOCT1 and decreased with increasing alkyl chain length, indicating that the inhibitory potential of TAAs on metformin uptake was greater in hOCT2 than in hOCT1 and increased with increasing alkyl chain length. The plasma concentration of metformin was elevated by the coadministration of tetrapropylammonium (TPrA) and tetrapentylammonium (TPeA), but not by tetramethylammonium (TMA) or tetraethylammonium (TEA). However, the plasma concentrations of TMA, TEA and TPrA were not changed by the coadministration of metformin. In conclusion, in vivo drug interactions between metformin and TAAs were caused only when metformin was coadministered with TAAs showing higher affinities for OCTs. Copyright 2007 John Wiley & Sons, Ltd. [source]

    Self-Assembled Monolayers of Alkoxy-Substituted Octadehydrodibenzo[12]annulenes on a Graphite Surface: Attempts at peri -Benzopolyacene Formation by On-Surface Polymerization

    Kazukuni Tahara Dr.
    Abstract Self-assembled monolayers of a series of tetraalkoxy-substituted octadehydrodibenzo[12]annulene (DBA) derivatives 1,c,g possessing butadiyne linkages were studied at the 1,2,4-trichlorobenzene (TCB) or 1-phenyloctane/graphite interface by scanning tunneling microscopy (STM). The purpose of this research is not only to investigate the structural variation of two-dimensional (2D) monolayers, but also to assess a possibility for peri -benzopolyacene formation by two-dimensionally controlled polymerization on a surface. As a result, the formation of three structures, porous, linear, and lamella structures, were observed by changing the alkyl chain length and the solute concentration. The formation of multilayers of the lamella structure was often observed for all compounds. The selection of molecular networks is basically ascribed to intermolecular and molecule,substrate interactions per unit area and network density. The selective appearance of the linear structure of 1,d is attributed to favorable epitaxial registry matching between the substrate lattice and the overlayer lattice. Even though the closest interatomic distance between the diacetylenic units of the DBAs in the lamella structure (,0.6,nm) is slightly larger compared to the typical distances necessary for topochemical polymerization, the reactivity toward external stimuli (electronic-pulse irradiation from an STM tip and UV irradiation) was investigated. Unfortunately, no evidence for polymerization of the DBAs on the surface was observed. The present results indicate the necessity for further designing a suitable system for the on-surface construction of structurally novel conjugated polymers, which are otherwise difficult to prepare. [source]

    Synthesis of 9,9-Dialkyl-4,5-diazafluorene Derivatives and Their Structure,Activity Relationships Toward Human Carcinoma Cell Lines

    CHEMMEDCHEM, Issue 4 2010
    Qiwei Wang
    Abstract A homologous set of 9,9-dialkyl-4,5-diazafluorene compounds were prepared by alkylation of 4,5-diazafluorene with the appropriate alkyl bromide and under basic conditions. The structures of these simple organic compounds were confirmed by spectroscopic techniques (FTIR, NMR, and FABMS). Their biological effects toward a panel of human carcinoma cells, including Hep3B hepatocellular carcinoma, MDAMB-231 breast carcinoma, and SKHep-1 hepatoma cells, were investigated; a structure,activity correlation was established with respect to the length of the alkyl chain and the fluorene ring structure. The relationship between the mean potency [log(1/IC50)] and alkyl chain length was systematically studied. The results show that compounds with butyl, hexyl, and octyl chains exhibit good growth inhibitory effects toward these three human carcinoma cell lines, and the 9,9-dihexyl-4,5-diazafluorene further exhibits antitumor activity in athymic nude mice Hep3B xenograft models. For the structurally related dialkylfluorenes that lack the diaza functionality, in,vitro cytotoxicity was not observed at clinically relevant concentrations. [source]

    Structure,activity relationships for acute and chronic toxicity of alcohol ether sulfates

    Scott D. Dyer
    Abstract Acoholethersulfates(AES)areanionicsurfactantscommonlyusedinconsumerproducts. Commercial AES alkyl chain lengths range from C12 to C18, with ethoxylate (EO) units ranging from 1 to 5. Alkyl sulfate is a special case of AES with no EO units. Acute and chronic toxicity tests using Ceriodaphnia dubia via a novel flowthrough method were conducted with 18 AES compounds to derive SARs for effects assessment. In general, acute toxicity (48-h LC50) increased with increased alkyl carbon chain length and decreased with increased numbers of EO units. Parabolic structure,chronic (7-d) toxicity relationships were observed for endpoints such as the no-observed-effect concentration, lowest-observed-effect concentration, maximum acceptable toxicant concentration, EC20, and EC50. A linear relationship of the fractional negative-charged surface area (FNSA-3) with acute toxicity was also determined. FNSA-3 refers primarily to the polar head group of AES and secondarily to the alkyl chain. Seventy percent of the variance in the chronic data was addressed with a quadratic equation relating toxicity to alkyl chain length and EO units. Alternatively, the molecular descriptors FNSA-3 and S3P (3,p, which is the simple, third-order path index) were also found to address most of the data nonlinearity. A chronic test conducted with a mixture of four AES components indicated additivity, leading to the support of the performance of an effects assessment of AES as a mixture. [source]