Synthesis and surface activity of mono- and diphosphate ester mixture with different alkyl chain length

A series of alkyl phosphate esters were synthesized and each of them was a mixture of monophosphate and diphosphate esters in a high or low mono/dimole ratio. The structure of hexadecyl phosphate ester with a low mono/dimole ratio was confirmed by FTIR, ¹H NMR, and³¹P NMR. The surface tensions of these alkyl phosphate esters were analyzed using a surface tensionmeter. The results showed that the critical micelle concentration (CMC) and critical surface tension (γ_CMC) of phosphate esters with a high mono/di ratio decreased with the increase of alkyl chain length. However, for the phosphate esters with a low mono/di ratio, the CMC, and γ_CMC decreased initially and increased afterwards with the increase of alkyl chain length. Meanwhile, the butanol and octanol phosphate esters with a high mono/di ratio had higher CMC and γ_CMC than their low mono/di ones, while the dodecyl and hexadecyl phosphate esters presented an opposite result. The results indicated that the mono- and diphosphate esters in the mixture may have a synergistic effect on the arrangement of molecules.     

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。     

The effect of the alkyl chain length on the mesomorphic properties of new lactic acid derivatives

New series of lactic acid derivatives with alkyl terminal chain have been synthesised and their mesomorphic properties studied. We have varied the length of chiral and non-chiral terminal alkyl chains and found that prolonging both chains has a strong effect on the SmA*–SmC* phase transition. Most of the new materials exhibit only paraelectric SmA* phase; for homologues with a longer non-chiral chain (m ≥ 10), the ferroelectric (SmC*) phase appears below the SmA* on cooling and persists down to a room temperature. The role of the chiral terminal chain in the molecule is quite opposite – only its short length supports the existence of ferroelectric phase. Additionally, a hexatic phase appeared below the SmA*–SmC* phase sequence for several homologues at low temperatures. All materials have been studied using standard experimental techniques (differential scanning calorimetry (DSC), texture observations, polarisation and tilt angle measurements, etc.). Liquid crystalline properties of new materials have been compared with the previously prepared and studied lactic acid derivatives.     

Synthesis and the effect of alkyl chain length on photochromic properties of diarylethene derivatives

A new class of photochromic diarylethenes bearing pyrrole and thiophene units with different length of alkyl chains at 2-position of thiophene rings have been synthesized. Their characteristics, including photochromism and fatigue resistance were investigated systematically, and each diarylethene derivative showed good photochromic properties whether in solution or in PMMA films. The alkyl group moiety was connected directly to the central cyclopentene ring as a heteroaryl unit and availably participated in photoisomerization reaction. And some properties, for example, the conversion ratio in the photostationary state(PSS) and the absorption coefficient of the ring-closed isomers in acetonitrile were significantly affected by the alkyl chain length. The results revealed that substituents of alkyl chain played an important role in the photoisomerization process of diarylethenes.     

Synthesis and the effect of alkyl chain length on optoelectronic properties of diarylethene derivatives

Photochromic symmetrical diarylethene derivatives 1a-6a bearing different long alkyl chains at 2-position of thiophene rings have been synthesized and their structures have been determined by single-crystal X-ray diffraction analysis. The effect of alkyl chain length on their optoelectronic properties, such as photochromism in solution as well as in the crystalline phase and electrochemical performance was investigated in detail. These diarylethenes have showed good photochromic behavior both in solution and in the single crystalline phase. Introduction of the long alkyl chains at 2-position of bis(5-formyl-3-thienyl)perfluorocyclopentene increased the absorption coefficients of both open- and closed-ring isomers and induced bathochromic shifts of the maximal wavelength absorption of the closed-ring isomers. The long alkyl chains can also decrease the cyclization/cycloreversion quantum yields and the oxidation potentials. The cyclic voltammetry indicated that the band gap of these diarylethene derivatives was significantly affected by the alkyl chain length.     

Thermal degradation of poly(alkyl acrylates). III. A secondary ester: Isopropyl acrylate

A quantitative analysis of the products of the thermal degradation of poly(isopropyl acrylate) has been made principally by the application of GLC and mass and infrared spectrometry. The major products are carbon dioxide and propylene. The carbon dioxide/propylene ratio is very low in the initial stages but converges to approximately 0.6 late in the reaction. There is some tendency to autocatalysis in the production of propylene. Carbon monoxide and isopropanol are very minor products, and there is no chain fragment fraction as in the degradation products of the poly(primary acrylates). Changes in the infrared spectrum of the polymer during degradation are in accordance with the formation of these products and the reaction characteristics are accounted for mechanistically.     

The effect of alkyl chain of the imidazolium ring on the poly(o-methoxyaniline)/ionic liquid supercapacitor performance

Journal of Solid State Electrochemistry - New materials can be developed using a known compound with enhanced properties modifying and controlling its microstructure, morphology, and density of...     

Effect of alkyl chain length in the terminal ester group on mesomorphic properties of new chiral lactic acid derivatives

Two series of new liquid crystalline lactic acid derivatives with a terminal ester group have been synthesised. The effect of this ester unit and the length of its alkyl chain on the mesomorphic and dielectric properties of the compounds exhibiting a broad temperature range of chiral smectic phases have been studied. We found that the mesomorphic behaviour and phase transition temperatures are strongly affected by the molecular architecture. Depending on the alkyl chain length in the terminal ester unit, the studied materials exhibited paraelectric smectic A*, ferroelectric tilted smectic C* and antiferroelectric smectic C_A* phases over a broad temperature range. The physical properties of the compounds have been studied by optical polarising microscopy, differential scanning calorimetry, electro-optic measurements, small-angle X-ray scattering and dielectric spectroscopy. Furthermore, the homologues with short terminal alkyl chains showed a very small layer shrinkage at the transition from the orthogonal SmA* to the tilted SmC* phase, which is a characteristic feature of ‘de Vries-type’ behaviour.     

The effect of the alkyl chain length of the tetraalkylammonium cation on CO2 electroreduction in an aprotic medium

The effect of tetraalkylammonium cation (TAA⁺) chain length on CO₂ electroreduction is investigated on an Ag electrode in a DMF solution. Linear sweep voltammetric (LSV) studies show that the onset potentials of CO₂ reduction move to increasingly negative potentials upon increasing the alkyl chain length of the tetraalkylammonium cation of the supporting electrolyte. Density functional theory (DFT) computations indicate that the onset potential of CO₂ reduction is dependent on the strength of ion pairing between TAA⁺ cation and the electrogenerated CO₂^.−. CO₂ disturbance experiments reveal that the peak current of CO₂ reduction is determined by the quantity of TAA⁺ cation adsorbed on the Ag surface.     

Mercury extraction by ionic liquids: temperature and alkyl chain length effect

The preliminary results described here show the complete transfer of Hg(II) ions, in the absence of a chelating agent in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids; the lag time required to gain the quantitative metal ion partition turned out to be strongly dependent both on alkyl chain length on the imidazolium ring and on the working temperature.     

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.     

The effect of alkyl chain length on the thermodynamic properties of the half esters of o-phthalic acid

The temperature, heat and entropy of fusion of four half esters of o-phthalic acid have been measured. These values are compared to other aromatic acid properties on the basis of molecular weight. The calorimetric data have an accuracy of ±5% and agree well with values predicted from simple entropy, geometric and electronic considerations.     

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.     

Liquid crystalline properties of dissymmetric molecules VI. The effect of alkyl chain length on molecular arrangement in the smectic A phase in three-aromatic-ring systems with two ester groups

The effect of alkyl and alkoxy chain lengths on the layer structures of smectic A and C phases has been examined by X-ray diffraction measurements on three isomeric systems: 4-alkoxyphenyl and 4-n-alkylphenyl 4-[(4-octyloxyphenyl)carbonyloxy]benzoates (1); 4-octyloxyphenyl 4-[4-(octyloxyphenyl)carbonyloxy]benzoates (2); 4-octyloxyphenyl, 4-alkoxyphenyl and 4-n-alkylphenyl terephthalates (3); and p-phenylene 4-octyloxybenzoates, 4-alkoxybenzoate and 4-n-alkylbenzoate (4). Although all the derivatives exhibit smectic A and/or C phases having a monolayer arrangement of the molecules, the layer spacings are considerably affected by alternation of the ester linkages. The layer spacings for the homologues of 1 are a little shorter than the calculated molecular lengths, while those for 2 agree with the calculated molecular lengths. The layer spacings for 3 show a notable even-odd alternation in the higher homologues. The results are discussed in terms of a subtle change in the molecular structures due to replacement of the ester groups.     

Liquid crystalline properties of dissymmetric molecules VI. The effect of alkyl chain length on molecular arrangement in the smectic A phase in three-aromatic-ring systems with two ester groups

The effect of alkyl and alkoxy chain lengths on the layer structures of smectic A and C phases has been examined by X-ray diffraction measurements on three isomeric systems: 4-alkoxyphenyl and 4-n-alkylphenyl 4-[(4-octyloxyphenyl)carbonyloxy]benzoates (1); 4-octyloxyphenyl 4-[4-(octyloxyphenyl)carbonyloxy]benzoates (2); 4-octyloxyphenyl, 4-alkoxyphenyl and 4-n-alkylphenyl terephthalates (3); and p-phenylene 4-octyloxybenzoates, 4-alkoxybenzoate and 4-n-alkylbenzoate (4). Although all the derivatives exhibit smectic A and/or C phases having a monolayer arrangement of the molecules, the layer spacings are considerably affected by alternation of the ester linkages. The layer spacings for the homologues of 1 are a little shorter than the calculated molecular lengths, while those for 2 agree with the calculated molecular lengths. The layer spacings for 3 show a notable even-odd alternation in the higher homologues. The results are discussed in terms of a subtle change in the molecular structures due to replacement of the ester groups.     

The esterolytic activity of poly(1-methyl-4- and -5-vinylimidazole) in water.

The water solubility of poly(1-Me-5-VIm) has made it possible to achieve phenomenal rate enhancements and to gain even greater insight into the mechanism of catalysis by polymeric imidazoles. The poly(1-Me-5-VIm)-catalyzed hydrolysis of S12- exhibited saturation in excess catalyst nad in excess substrate. Inhibition of the poly(1-Me-5-Vim) catalyzed hydrolysis of Sn- type substrates by analog inhibitors was also observed. The saturation apparently did not follow a simple Michaelis-Menten mechanism; however, the results could be rationalized by analogy to certain enzymatic systems. Multisite enzymes have long been known to display kinetic patterns different from that exhibited by enzymes with only one active site, i.e. such phenomena as sigmoidal rate vs [S] plots. These phenomena may arise entirely as a result of the multisite nature of the enzyme. Consequently, a synthetic macromolecular catalyst with multiple sites might also be expected to display such characteristics. The poly(1-Me-5-VIm)-catalyzed hydrolysis of S12- is apparently the first synthetic system in which such phenomena have been observed. The intermediacy of an apolar polymer substrate complex for the poly(1-Me-5-VIm)-catalyzed hydrolysis of S12- in water was given support by studies of the effect of temperature on the rate of hydrolysis. Activation parameters were determined for catalysis by 1,5-DMIm and by poly(1-Me-5-VIm). These results showed that the rate enhancement exhibited by the polymer was due entirely to a favorable entropy term.     

Interfacial regions governing internal cavities of dendrimers. Studies of poly(alkyl aryl ether) dendrimers constituted with linkers of varying alkyl chain length

This report deals with a study of the properties of internal cavities of dendritic macromolecules that are capable of encapsulating and mediating photoreactions of guest molecules. The internal cavity structures of dendrimers are determined by the interfacial regions between the aqueous exterior and hydrocarbon like interior constituted by the linkers that connect symmetrically sited branch points constituting the dendrimer and head groups that cap the dendrimers. Phloroglucinol-based poly(alkyl aryl ether) dendrimers constituted with a homologous series of alkyl linkers were undertaken for the current study. Twelve dendrimers within first, second, and third generations, having ethyl, n-propyl, n-butyl, and n-pentyl groups as the linkers and hydroxyl groups at peripheries in each generation, were synthesized. Encapsulation of pyrene and coumarins by aqueous basic solutions of dendrimers were monitored by UV-vis and fluorescence spectroscopies, which showed that a lower generation dendrimer with an optimal alkyl linker presented better encapsulation abilities than a higher generation dendrimer. Norrish type I photoreaction of dibenzyl ketone was carried out within the above series of dendrimers to probe their abilities to hold guests and reactive intermediate radical pairs within themselves. The extent of cage effect from the series of third generation dendrimers was observed to be higher with dendrimers having an n-pentyl group as the linker.     

Nucleophilic cosubstitution of poly(dichlorophosphazene) with alkyl ether and amino acid ester

The nucleophilic substitution reaction of poly(dichlorophosphazene) with sodium 2‐methoxyethoxide and glycine ethyl ester has been studied in detail. Polymers prepared with different methods have been characterized by ¹H NMR, and the results reveal that the addition sequence of the two nucleophilic reagents is an important factor in determining the structure of the resultant polymer. If alkyl ether is added first, the subsequently introduced amino acid ester not only reacts with residual P? Cl but also attacks the alkyl ether side units present by replacing either the whole group or just ? OCH₃. As a result, a new kind of side group (? OCH₂CH₂NHCH₂COOC₂H₅) can be detected in the macromolecule. To obtain polymers with desired compositions {poly[(methoxyethoxy)_x(ethylglycino)_yphosphazene]}, the amino acid ester should be introduced initially to react with poly(dichlorophosphazene), and it should be followed by the alkyl ether. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2417–2425, 2005     

Synthetic high-charge organomica: effect of the layer charge and alkyl chain length on the structure of the adsorbed surfactants

A family of organomicas was synthesized using synthetic swelling micas with high layer charge (Na(n)Si(8-n)Al(n)Mg(6)F(4)O(20)·XH(2)O, where n = 2, 3, and 4) exchanged with dodecylammonium and octadecylammonium cations. The molecular arrangement of the surfactant was elucidated on the basis on XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas was investigated by (13)C, (27)Al, and (29)Si MAS NMR. The arrangement of alkylammonium ions in these high-charge synthetic micas depends on the combined effects of the layer charge of the mica and the chain length of the cation. In the organomicas with dodecylammonium, a transition from a parallel layer to a bilayer-paraffin arrangement is observed when the layer charge of the mica increases. However, when octadecylammonium is the interlayer cation, the molecular arrangement of the surfactant was found to follow the bilayer-paraffin model for all values of layer charge. The amount of ordered conformation all-trans is directly proportional of layer charge.