Preparation of benzalkonium salts differing in the length of a side alkyl chain

Benzalkonium salts are widely used as disinfectants, biocides and detergents,among a variety of other applications. The cationic surface-activity of these salts determines their potential to act as a biocide on both target and non-target organisms. In this study, a quick synthesis of a complete set of the benzalkonium salts differing in the length of an alkylating chain (from C(2) to C(20)) is described. Moreover, their (1)H-NMR, HPLC-MS, TLC and HPLC analysis were recorded.     

Influence of the alkyl side chain length on the room-temperature phosphorescence of organic copolymers

Pure organic room-temperature phosphorescence(RTP) materials have attracted wide attention owing to their excellent luminescent properties and great potential in various applications. In this work, iminostilbene and its analogues are applied to realize RTP emission by copolymerizing with acrylamide. It can be concluded that the growth of alkane chain in monomers can enhance the lifetime and photoluminescence quantum yield of RTP emission, and polymers with the larger conjugated structure of the ...     

Polymerization of surface-active monomers. II. Polymerization of quarternary alkyl salts of dimethylaminoethyl methacrylate with a different alkyl chain length

The cationic monomers (C_NBr), obtained by quarternization of dimethylaminoethyl methacrylate with n-alkyl bromide containing varying carbon number (N = 4, 8, 12, 14, and 16) were polymerized with radical initiators in water and various organic solvents. The degree of polymerization of the resulting polymers was determined by GPC measurements on poly(methyl methacrylate) samples derived from them. The rate of polymerization of the micelle-forming monomers (N = 8, 12, 14, and 16) in water increases with increasing a chain length of alkyl group, whereas it is little dependent on N in isotropic solution in dimethylformamide. The data on the degree of polymerization for the polymers of C₄Br, C₈Br, and C₁₂Br show that the polymerization of C₁₂Br with azo initiators in water and benzene gives polymers with a very high degree of polymerization. The results obtained here suggest that highly developed or relatively rigid, aggregated structures of monomers in solution are responsible for the formation of the polymers with a very high degree of polymerization, in addition to an enhanced rate of polymerization. Also considered are the relation of the molecular weight of poly(C₁₂Br) to the viscosity data in chloroform and methanol.     

Effect of alkyl side chain length on the properties of polyetherimides from molecular simulation combined with experimental results

Three polyetherimides (PEIs) with the same backbone of Ultem 100 but different lengths of the alkyl side chains were simulated by using molecular dynamics and molecular mechanics techniques to investigate the effect of side chain length on their properties and physical mechanism behind. Simulation results, which are consistent to the experimental data, show that PEI‐5 with four methylene units in each alkyl side chain has higher T_g (glass transition temperature) and higher tensile strength, but lower tensile elongation at break than those of PEI‐6 with five and PEI‐8 with seven methylene units in each alkyl side chain. However, unlike the traditional phenomena, conformational analysis provides that PEI‐5 with the highest T_g gives the highest flexibility to the polymer chain, whereas PEI‐8 with the lowest T_g imparts the lowest flexibility resulting from attachment of longer alkyl side chain increase the rigidity of backbone. From the calculated ratio of the accessible volume to the total volume for each system, the highest ratio of PEI‐8 indicates that long alkyl side chains generate more free volume than short side chains, acting as an internal plasticizer in bulk structure. It is the internal plasticizing effect that is predominantly responsible for the abnormal properties, instead of the rigidity from side chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 595–599, 2010     

Amino acid side chain interactions in the presence of salts

The effects of salt on the intermolecular interactions between polar/charged amino acids are investigated through molecular dynamics simulations. The mean forces and associated potentials are calculated for NaCl salt in the 0-2 M concentration range at 298 K. It is found that the addition of salt may stabilize or destabilize the interactions, depending on the nature of the interacting molecules. The degree of (de)stabilization is quantified, and the origin of the salt-dependent modulation is discussed based upon an analysis of solvent density profiles. To gain insight into the molecular origin of the salt modulation, spatial distribution functions (sdf's) are calculated, revealing a high degree of solvent structuredness in all cases. The peaks in the sdf's are consistent with long-range hydrogen-bonding networks connecting the solute hydrophilic groups, and that contribute to their intermolecular solvent-induced forces. The restructuring of water around the solutes as they dissociate from close contact is analyzed. This analysis offers clues on how the solvent structure modulates the effective intermolecular interactions in complex solutes. This modulation results from a critical balance between bulk electrostatic forces and those exerted by (i) the water molecules in the structured region between the monomers, which is disrupted by ions that transiently enter the hydration shells, and (ii) the ions in the hydration shells in direct interactions with the solutes. The implications of these findings in protein/ligand (noncovalent) association/dissociation mechanisms are briefly discussed.     

Imination of pyridinium and quinolinium salts

A new method for imination of N-alkyl pyridinium- and quinolinium salts is described. It involves a low temperature oxidation of a solution of appropriate substrates in liquid ammonia with potassium permanganate.     

Influence of alkyl chain length on phosphate self-assembled monolayers

A series of alkyl phosphates with alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in alkyl phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for alkyl phosphates with alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average alkyl chain tilt angle of 30 degrees to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretching modes in the PM-IRRAS spectra to lower wave numbers was observed. These findings imply a higher two-dimensional crystallinity of the films derived from alkyl phosphates with a longer alkyl chain length.     

Fine-tuning of polymer photovoltaic properties by the length of alkyl side chains

This paper reports the synthesis and characteristics of a series of alkyl-substituted planar polymers. The physical properties are carefully tuned to optimize their photovoltaic performance. Depending on the length of soluble alkyl side chains which modify the structural order and orientation substantially in polymer backbones, the device performance can be improved significantly. The tuning of HOMO energy levels optimized polymers’ spectral coverage of absorption and their hole mobility, as well as miscibility with fullerene; all these efforts enhanced polymer solar cell performances. The shortcircuit current, Jsc for polymer solar cells was increased by adjusting polymer chain packing ability. It was found that films with well distributed polymer/fullerene interpenetrating network exhibit improved solar cell conversion efficiency. Enhanced efficiency up to 5.8% has been demonstrated. The results provide important insights about the roles of flexile chains in structure-property relationship for the design of new polymers to be used in high efficient solar cells.     

微乳液的热力学性质 I: 芳烃类的侧链链长对微乳液热力学函数影响

本文研究以非离子型表面活性剂-正辛醇-水-芳烃类所组成的微乳液, 探讨醇从油相转移到界面相时的自由能变化, 以及温度对自由能的影响。计算出熵和焓的变化, 发现在实验范围内, 上述热力学函数的对数值与芳烃侧链的碳原子数(n)呈线性关系。这些关系式对微乳液的构成和稳定性的讨论是重要的, 还对几种芳烃异构体所构成的微乳液的热力学函数进行了实验和讨论。     

Effects of alkyl chain length on surface and micellar properties of octaethyleneglycol-n alkyl ethers

Summary Surface and micellar properties of a homologous series of Octaethylene glycol-n-alkyl ethers (C _n E₈;n = 9 to 15) have been studied in aqueous solutions by the surface tension measurements. The effects of the alkyl chain length comprising even and carbon numbers have been examined in order to evaluate the surface free energy G _A-W and the standard free energy G _m for the micellization obtained from their surface tension data. The areas per molecule and the equilibrium surface tension values at the CMC decreased with an increasing carbon number and they showed zigzag curves by the difference in even and odd carbon numbers.These findings may be attributed to the differences in the molecular orientation between the molecules with even carbon number and ones with odd carbon number on the air-water interface at CMC. G _A-W values decreased linearly with an increasing alkyl chain length but did not show a zigzag line by the differences in even and odd carbon numbers. This suggests that the molecular orientation is not influenced by the difference between their even and odd carbon numbers in the alkyl chain on the surface of the very diluted solution, and their molecules form some stable adsorbed films with an increase of the alkyl chain length. A division of G _A-W into the contribution made both by the hydrophilic group G _A-W (-W) and by the hydrophobic group G _A-W (-CH₂-) was attempted as follows; G _A-W (-CH₂-) = – 0.80 kcal/mol and G _a-W (-W) = + 0.15 kcal/mol.The free energy changes G _m of micellization were discussed on the basis of the CMC data obtained from the surface tension measurements by treating the formation of micelles as analogous to phase separation, and the contribution from the each moieties in the molecule were calculated as follows; G _m (-CH₂-) = – 0.68 kcal/mol and G _m (-W) = + 1.54 kcal/mol. The difference between G _A-W and G _m is discussed using their data.     

Surface properties of poly(N-monoalkylmaleamic acid-alt-styrene) sodium salts: effect of the molecular weight and the side chain length

The surface properties of poly(N-monoalkylmaleamic acid-alt-styrene) sodium salts are studied as a function of the molecular weight and the size of the linear alkyl lateral chain of the polyelectrolyte. The experimental results are well described by the Gibbs-Szyszkowski treatment. Both the surface tension behavior and the standard free energy of adsorption depend on the polyelectrolyte side chain and on the average molecular weight, M(w). An M(w)-dependent contribution to the free energy of adsorption ranging from -1.21 to -1.05 kJ for mole of methylene groups is found. The area covered by monomer units increases with M(w) and the sizes of side chains are similar to those reported in small-molecule systems. The nature of the functional group amide in the side chain has practically no effect on the surface properties as compared with the ester group in this kind of polyelectrolytes.     

Dependence of the conformational equilibrium of alkyl azidoformates on the length of the carbon chain of the alkyl group

Conclusions An empriical dependence of the conformational equilibrium constant of alkyl azidoformates on the length of the alkyl group carbon chain was derived on the basis of an experimental study.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 452–455, February, 1989.     

Blue light-emitting polyfluorenes containing dibenzothiophene-S,S-dioxide unit in alkyl side chain

Blue light-emitting polyfluorenes containing dibenzothiophene-S,S-dioxide(SO) unit in alkyl side chain(PF-FSOs and PF-CzSOs) were synthesized. All the polymers show high thermal stability with the decomposition temperatures over400 °C. The highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) energy levels of the copolymer slightly decrease with the increase of SO content in side chain. PL spectra of the polymers show slightly red shift and broadening with the increase of solvent polarities, indicating unremarkable intramolecular charge transfer(ICT) effect in the polymers containing SO unit in alkyl side chain. EL spectra of the polymers are almost unchanged in the current densities from 100 to 400 mA cm.2, indicating the superb EL stability of the resulted polymers. The EL spectra of the copolymers exhibit obvious blue-shift and narrowing with the CIE of(0.18, 0.11) for PF-FSO10 and(0.17, 0.11) for PF-CzSO10, respectively,compared with PF-SO10 containing SO unit in main chain with the CIE of(0.16, 0.17) and PFO with the CIE of(0.18, 0.18).The superior device performances were obtained with the luminous efficiency(LEmax) of 1.17 and 0.68 cd A.1 for PF-FSO15 and PF-CzSO20, respectively, compared with the LEmax of 0.37 cd A.1 for PFO. The results indicate that linking SO unit to alkyl side chain of the polyfluorene is a promising strategy for efficient blue light-emitting polymers.     

Microemulsions: Effect of alkyl chain length of alcohol and alkane

In microemulsions consisting of four components, i.e. detergent — water — oil — cosurfactant, the free energy of transfer from the continuous oil phase to the interfacial region for the cosurfactant is reported. From the effect of temperature on the free energy, the entropy and the enthalpy values are also reported. The effect of chain length of the alcohol (cosurfactant) is also described. It is further shown, that if the oil phase consists of hexadecane, then the free energy changes as a linear function of the number of carbon atoms in the cosurfactant. On the other hand, if the oil phase is benzene, the cosurfactant chain length has very little effect. These data are analyzed with respect to the microemulsion structure and stability.     

Effect of the surfactant alkyl chain length on the stabilisation of lyotropic nematic phases

Lyotropic quaternary mixtures of potassium alkanoates (KCx) and sodium alkyl sulphates (NaCxS), where x is the number of carbon atoms in their alkyl chains, were prepared to investigate the effect of the surfactant alkyl chain length on the stabilisation of lyotropic nematic phases. The lyotropic mixtures investigated were formed by the dissolution of KCx (NaCxS) surfactants in the mixture of Rb₂SO₄/1-decanol/water (Na₂SO₄/1-decanol/water), separately. The uniaxial-to-biaxial nematic phase transitions were identified from the temperature dependence of the birefringences of the nematic phases by means of laser conoscopy. The micelle dimensions were obtained from small-angle X-ray scattering measurements. It was observed that the increase in the surfactant alkyl chain length causes the micellar growth in the plane perpendicular to the main amphiphile bilayer. The surfactant alkyl chain length plays a key role on the shape anisotropy of micelles, which triggers the orientational fluctuations that are responsible for the stabilisation of the different lyotropic nematic phases.     

Quantum dot fluorescence as a function of alkyl chain length in aqueous environments

In this work, we examine the dependence of the fluorescence quantum yield of water-soluble CdSe/ZnS quantum dots on the local environment. The hydrophobicity of the local environment was modified by using different alkyl chain lengths in a set of oligo-ethylene glycols. Our results show that the quantum yield of CdSe/ZnS quantum dots is highest for the longest alkyl chain length, suggesting that a more hydrophobic environment is beneficial for generating bright, water-soluble quantum dots.     

Thermodynamic study of the process of micellization of long chain alkyl pyridinium salts in aqueous solution

The molality dependence of specific conductivity of pentadecyl bromide, cetylpyridinium bromide and cetylpiridinium chloride in aqueous solutions has been studied in the temperature range of 30–45 °C. The critical micelle concentration (cmc) and ionization degree of the micelles, β, were determined directly from the experimental data. Thermal parameters, such as standard Gibbs free energy \Updelta G_m⁰ , \Updelta G_{m}^{0} , enthalpy \Updelta H_m⁰ \Updelta H_{m}^{0} and entropy \Updelta S_m⁰ , \Updelta S_{m}^{0} , of micellization were estimated by assuming that the system conforms to the pseudo-phase separation model. The change in heat capacity on micellization \Updelta C_p , \Updelta C_{p} , was estimated from the temperature dependence of \Updelta H_m⁰ . \Updelta H_{m}^{0} . An enthalpy–entropy compensation phenomenon for the studied system has been found.     

Effect of the alkyl chain length of 1,1′-binaphthyl esters in lipase-catalyzed amidation

Lipase-catalyzed amidation of 2-[2-(ethoxycarbonyl)ethyl]-1,1′-binaphthyl [(±)-3] yielded optically active (S)-3 and 2-[2-(2-cyanoethylaminocarbonyl)ethyl]-1,1′-binaphthyl [(R)-6a] with high enantiomeric excess. For these lipase-catalyzed amidations, the optimal alkyl chain length between the binaphthyl ring and the ester group was determined to be an ethylene spacer.