Preparation and Characterization of Amine Modified Porous Polymer for Rplc

Abstract

The retention behaviour and selectivity of various aromatic compounds, including halobenzenes and a IkyIbenzenes, were examined on the stationary phase of chloromethylated polystyrene(CMS) beads, of which the chloride group was substituted by the alkylamines: n-hexyl(C₆), n-octyl(C₈), n-decyl (C₁₀),n-dodecyl (C₁₂), n-tetradecyl (C₁₄) or n-hexadecy1 (C₁₆). Changes in the distribution coefficients of benzene derivatives are demonstrated not only by the changes of the eluent compositions but also by the changes of chain length in the stationary phase. In general, a longer alkyl chain in the stationary phase gives longer retention time and different selectivity. The effects of MeOH/H₂O ratios on retention and selectivity was also demonstrated on the C₁₄ stationary phase. Good separations of halobenzenes and alkyIbenzenes were obtained with C₁₄ stationary phase. Moreover, the retention time for samples was shortened by about a half compared to polystyrene stationary phase. These results show the chemical modification of CMS gel with long chain alkyl amines decreases tailing and provides new supports with different selectivities.     

Relationships between miscibility behavior and chemical structure of phospholipids in pseudobinary systems

The influence of chain length differences of cephalines and the influence of the head group methylation on the miscibility behavior of N-methylated phosphatidylethanolamine (PE) mixtures in aqueous dispersions were tested. Nine different phase diagrams were studied by means of differential scanning calorimetry. The phase diagrams of the five pseudobinary cephaline/cephaline/water systems (fatty acid chain length: C _n , n = 12–18) showed that in the high temperature L_α phase all the homologous cephalines were completely miscible. In the low-temperature phase a distinct succession of the phase diagram types was observed according to increasing chain length differences of the PEs: complete miscibilty (C₁₂/C₁₄; C₁₄/C₁₆), peritectic mixing behavior (C₁₂/C₁₆; C₁₄/C₁₈), eutectic mixing behavior (C₁₂/C₁₈). Furthermore four phase diagrams of pseudobinary phospholipid systems consisting of N-methylated PEs with different numbers of methyl groups and a constant length of fatty acid chains were investigated and compared. These four phase diagrams showed phase separations in the low-temperatures phase (gel phase). The width and the concentration range of the miscibility gaps changed systematically with increasing degree of methylation of the head group of the mixing components and are connected with different possibilities of PEs to form hydrogen bridges between the mixture components. Received: 26 August 1999/Accepted: 30 August 1999     

Mesomorphic and fluorescence properties of methyl 4-(4-alkoxystyryl)benzoates

A series of methyl 4-(4-alkoxystyryl)benzoates was synthesised and studied for liquid crystalline and fluorescence properties. The peculiarity of the reaction scheme involved condensation between 4-alkoxybenzaldehyde and 4-(methoxycarbonyl)benzyltriphenyl phosphonium bromide in dichloromethane without any phase separation. The compounds were found thermally stable up to 200°C. The banded or arced focal-conic fan texture of CrE phase was exhibited on cooling the compounds (with chain length > C₄) below the SmA phase. It was observed that increasing chain length up to C₁₀ enhances mesophase stability. No LC behaviour was manifested by small (up to C₃) and branched small chain (up to C₄) members of the series.     

Induction of ionic smectic C phases: a systematic study of alkyl-linked guanidinium-based liquid crystals

A series of ionic liquid crystals with an alkoxy biphenyl unit tethered via an alkyl spacer to a guanidinium head group were synthesised and the mesomorphic properties were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction (XRD; WAXS and SAXS). Whereas all symmetrical guanidinium chlorides with the same chain lengths in alkyl tail and spacer displayed enantiotropic SmA₂ phases, monotropic SmC₂ phases with 1–2 K temperature range were only formed for chain lengths ≥ C₁₀. Shifting the calamitic core more closely to the ionic head group by decreasing the tether length and simultaneously increasing the terminal alkyl chain improved the stability of both SmA and SmC phases considerably and led to enantiotropic SmC phases for the guanidinium chloride with C₁₄ alkyl tail and C₆ spacer. An even more pronounced effect was detected during anion exchange. Bromide, iodide, hexafluorophosphate, thiocyanate and triflate suppressed any SmC phase, whereas tetrafluoroborate behaved similar to chloride maintaining the SmC phase. However, acetate stabilised the SmC phase at the expense of the SmA phase. Based on temperature-dependant XRD measurements, a bilayer structure was proposed.     

A study of homologation and the occurrence of an SA-SC-SA sequence of phases in the 4-n-alkoxy-3-fluorophenyl 4-(5-n-alkyl-2-thienyl)benzoates

Abstract

Seventeen esters, derived from 4-n-alkoxy-3-fluorophenols and 4-(5-n-alkyl-2-thienyl)benzoic acids, have been prepared and their liquid crystal transition temperatures determined by thermal optical microscopy. On cooling the isotropic liquid, the S_A-S_C-S_A sequence of phases reported for the octyloxy-octyl and octyloxy-nonyl esters has been observed for certain other homologues, principally members of the 4-(5-n-nonyl-2-thienyl)benzoates. For these compounds, the temperature range of occurrence of the intermediate S_C phase decreases as the length of the alkoxy chain increases (for the hexyloxy-nonyl to dodecyloxy-nonyl esters) and the S_c phase is absent for the tetradecyloxy-nonyl homologue.     

PREPARATION AND SURFACE PROPERTIES OF NEW SULFOSUCCINIC DERIVATIVES OF FATTY POLYGLYCEROL ESTERS

ABSTRACT

The purpose of this work was to prepare hydrophilic anionic derivatives of polyglycerol esters in order to obtain new surfactants, characterized by the cosmetologic compatibility of renewable raw materials and the mildness of the chosen target surfactants. The derivatization has been done by esterification between polyglycerol esters (PGE) and maleic anhydride (MA) followed by sulfonation at the double bond, by sodium sulfite, getting sulfosuccinic derivatives. Polyglycerol esters composed of fatty acids of C₁₂ to C₁₆ and polyglycerol with chain length of n=l?10 served as raw materials for a number of sulfosuccinates. The surface properties (cmc; surface excess concentration, γ; surface molecular area, A; effectiveness, π_cmc; efficiency, _pC₂₀ contact angle, θ; wetting time and foam performance) of the raw materials and their anionic derivatives have been measured. The relationships between the chemical structure and the surface properties of the new surfactants have been established. Higher π_cmc and better foaming performance but lower wetting power were obtained by increasing hydrophilic chain length, to n=6. Over this length an opposite trend was found. A linear relationship beween log cmc and hydrophobic chain length was determined. Optimization of surface properties was accomplished by optimizing maleation conditions.     

Peripheral chain length-dependent complex phase behaviour in C3-symmetric hexa-alkylated liquid crystals

We report the thermal and self-assembly properties of C₃-symmetric liquid crystalline (LC) molecules consisting of a conformationally tunable triazole-based mesogen and six-fold alkyl chains. Unlike the LC compound (1) based on non-crystallisable octyl chains, 2 and 3, which have crystallisable dodecyl and tetradecyl chains, respectively, exhibit a cold crystallisation which only takes place under slow heating conditions (2°C/min). In contrast with the vertically interdigitated lamellar crystalline phase of 1, a laterally interdigitated bilayered lamellar structure driven by the crystallisation of the dodecyl or tetradecyl chains is observed in the cold crystallisation temperature range. In addition to their crystalline morphology, 2 and 3 show LC morphological behaviour distinct from that of 1, 2 and 3 exhibit a hexagonal columnar LC phase consisting of T-shaped conformers rather than the lamellar LC phase of 1. The morphological transformation from the lamellar (1) to the columnar phase (2 and 3) can be rationalised by the alleviation of the conformational energy of the longer alkyl chains. Consequently, the simple variation of alkyl chain length in the C₃-symmetric LC system results in contrasting thermal and assembly properties in the crystalline and LC phases.     

Structural and spectroscopic characterization of Cu(salen) complexes bearing long alkoxy chains

Cu(II) salen (salen?=?N,N′-ethylene-bis(salicylideneimine)) complexes bearing alkoxy chains of C₁₂ (1) and C₁₀ (2) in the salicylidene moieties were synthesized and subsequently characterized by several independent methods: single crystal X-ray diffraction, infrared spectroscopy, mass spectrometry, and UV-Vis spectroscopy. The solid state structures show that the spatial orientation and packing of the complexes are not affected by the alkyl chain length but by a coordinated solvent molecule, as demonstrated by the structure of 1 having methanol in an axial position.     

Effect of n-alkanes and peptides on the phase equilibria in phosphatidylcholine—water systems

Abstract

The phase equilibria in phosphatidylcholine (PC)-n-alkane-²H₂O systems have been studied to elucidate the driving forces for the transition between a lamellar liquid-crystalline (L _α) phase and a reversed hexagonal (H _II) phase. A tentative phase diagram for the system dioleoyl-PC (DOPC)-n-dodecane-²H₂O was determined. DOPC forms an L _α phase up to at least 90°C in excess water. However, an H _II phase was formed at room temperature at both low and high water concentrations in DOPC-n-dodecane-²H₂O mixtures. The phase equilibria were also studied in PC-n-dodecane-²H₂O systems containing PC with different degrees of acyl chain unsaturation. The water and dodecane concentrations required to induce the formation of an H _II (or isotropic) phase increase in the order dilinoleoyl-PC ～ DOPC < 1-palmitoyl-2-oleoyl-PC < dipalmitoyl-PC. The effect of n-alkanes with different chain lengths (C₈–C₂₀) on the phase equilibria in DOPC-n-alkane-²H₂O mixtures was studied. Although the number of alkane carbon atoms added per DOPC molecule was kept constant, the ability of the alkanes to promote the formation of an H _II phase was strongly chain length dependent; the ability decreased when going from octane to eicosane. Finally, some PC-peptide-²H₂O systems were investigated. Gramicidin (hydrophobic) had a similar influence on the phase equilibria as the alkanes. Melittin (amphiphilic) induced the formation of an isotropic phase, while insulin and duramycin (water soluble) had no, or a very limited, ability to induce a non-lamellar phase, respectively. Our results are discussed in the light of simple physical models dealing with the self-assembly of amphiphiles.     

Crystal‐smectic E mesophases in a series of 2‐(4‐n‐alkylphenyl)indenes

A series of 2‐(4‐n‐alkylphenyl)indenes (3) with different alkyl substituents (CH₃ to C₁₀H₂₁) were synthesized and systematically characterized using differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction compared with 2‐phenylindene (3a). Depending on the alkyl chain length, highly ordered crystal‐smectic E mesophases were observed and confirmed by X‐ray diffraction for the derivatives 3h–3k with heptyl to decyl chains (n = 6?9). For 3f with a pentyl side chain (n = 4), an X‐ray crystal structure analysis was carried out.     

6-氨基己酸及2-氨基乙磺酸C60加成物的合成及溶解性

水溶性Fullerenes (C₆₀)衍生物的制备对于C₆₀的生物学研究具有十分重要的意义. 氨基酸与C₆₀的胺化反应可得到水溶性的氨基酸C₆₀衍生物. 以C₆₀与过量6-氨基己酸或2-氨基乙磺酸(摩尔比为1∶10)于80 ℃搅拌反应24 h, 分别得到加成度为5和4的氨基酸C₆₀主产物, 产率按加入的C₆₀计算分别为30%, 28%. 氨基酸碳链的长度及加成产物在反应体系中能否及时沉淀析出影响和控制着加成度的大小. C₆₀[NH(CH₂)₅COOH]₅H₅ (3a), C₆₀(NHCH₂CH₂SO₃H)₄H₄ (6a)用柱层析进一步纯化, 其结构组成经元素分析, ¹H NMR, ¹³C NMR, IR所证实. 6a的水溶性受溶液pH的影响较小, 3a在不同pH缓冲溶液中的溶解性用光谱法测定, 分别为: pH＝10.25时为71.81 mg•mL^－1, pH＝7时为23.68 mg•mL^－1, pH＝3.36时为10.12 mg•mL^－1. 在波长273 nm处, 3a的摩尔消光系数为ε＝3.43×10⁴ L•mol^－1•cm^－1.     

Highly tilted antiferroelectric (R) enantiomers useful for the formulation of eutectic mixtures

ABSTRACT

Novel chiral three-ring (R) enantiomers were synthesised using optically active (R)-(?)-2-octanol. Properties, such as the sequence of phases, the transition temperatures and enthalpies, were tested by a polarising optical microscope and differential scanning calorimeter. An antiferroelectric smectic phase (SmC_A*) with a direct transition from the antiferroelectric to the isotropic phase (SmC_A*-Iso) was observed for three esters with an achiral C₃F₇CH₂O(CH₂)₃O– terminal chain. Bi- and multicomponent mixtures with a broad temperature range of the antiferroelectric phase and good electro-optical properties were formulated. Helical pitch of pure esters and mixtures was measured by spectrophotometry method.     

Improved Resolution of Hydrophobic Penicillin-binding Proteins and Their Covalently Linked Complexes on a Modified C18 Reversed Phase Column

ABSTRACT

Hydrophobic proteins have proven to be difficult to separate chromatographically. The use of a C18 reversed phase column with embedded polar groups showed improved separation and recovery of the hydrophobic, membrane associated, penicillin-binding proteins of Bacillus subtilis and their covalently linked complexes. The covalently linked complexes were generated by a time course reaction of the non-covalently associated complexes in the intact cell with the paired group specific reagent, cyanogen (C₂N₂).     

Stable frustrated phases in chiral liquid crystals derived from optically active (R)- and (S)-3-ethylmercapto-2-methylpropionic acids

Highly optically pure (R)- and (S)-3-ethylmercapto-2-methylpropionic acids were synthesized by using optically active (D)- and (L)-2,10-camphorsultams as chiral auxiliaries, respectively. Their derivatives, (R)- and (S)-EMMPNmB (m=6-12), were prepared for investigation. Microscopic texture observations demonstrated that the materials possess three stable frustrated phases: BP, TGB_A* and TGB_C* phases. Interestingly, it was found that the N* phase behaves as an intermediary phase between BP and TGB_A* phases in a rather narrow temperature range (calc. 0.5-1.4°C). A study of the racemic mixture, (±)-EMMPNmB (m=10), indicated that the chirality of the molecule could suppress the formation of smectic phases in the heating process. An increase of alkyl chain length favoured the formation of the TGB phases particularly, in accompaniment with a change of TGB phases from monotropic to enantiotropic. Moderate maximum P _S values (calc. 14-19 nC cm^-2) and apparent tilt angle (calc. 20°) were obtained for the TGB_C* phase in a surface stabilized ferroelectric liquid crystal geometry.     

Steric effect on the formation of columnar phases in β-diketonate copper(II) complexes

A systematic study of the mesomorphic properties of three series of copper(II) complexes based on β-diketonate ligands containing branched side chains is reported. These disc-like compounds have four, six and eight flexible alkoxy side chains appended to the central core, in which two or four side chains were substituted by bulkier secondary alkoxy groups: 1-methylbutyloxy R ' = C₅(2°) or 1-methylheptyloxy R ' = C₈(2°). The mesomorphic results indicated that at least eight side chains are required to form stable columnar mesophases; other compounds with four or six side chains are not mesogenic regardless of the combination of the carbon length on the alkoxy or secondary alkoxy groups of the side chains. The compounds 3 with shorter R ' = C₅(2°) side chains were all non-mesogenic regardless of the carbon length of three alkoxy side chains (R = C₈, C₁₀, C₁₂) used. However, when the longer 1-methylheptyloxy side chain R ' = C₈(2°) was substituted, the compounds 3b-3e with various alkoxy groups (R = C₆, C₇, C₈, C₁₀, C₁₂) exhibited columnar phases. The mesophases were characterized and identified as columnar hexagonal phases (Col_h), as expected, by thermal analysis and optical polarized microscopy. The presence of the introduced secondary alkoxy groups apparently appeared to influence the formation of columnar phases. The clearing points were relatively lower than other similar copper(II) compounds not substituted by secondary alkoxy side chains.     

EMULSIFICATION BY CHEMICALLY MODIFIED OVALBUMIN

Enhancement of emulsifying properties of a model protein, ovalbumin, was achieved by covaient attachment of hydrophobic groups using various esters of N-hydroxysuccinimide. It was found that the resulting modified proteins were much better emulsifiers than the native ovalbumin, even at low modification degree (20-30% of available amine groups): in tetradecan-water emulsions oil separation was observed within a few hours, when 0·7 mg/ml native ovalbumin was used, compared to about one month until separation was observed when the modified proteins were used. The use of highly modified proteins prevented completely oil separation (at least two months); for example, emulsions prepared with 51% modified proteins with C₃, C₆, showed no change in droplet size distribution even 50 days after preparation. The effect of chain length on emulsification was also investigated: an optimal chain length (Cg) was found, for both low and high modifications.     

High Performance Liquid Chromato-Graphy Separations of Nitrosamines. II. Acyclic Nitrosamines

Abstract

The separation of acyclic nitrosamines by HPLC using a β-cyclodextrin bonded silien gel column and a C₁₈ reversed phase column was evaluated. Four groups of nitrosamines were used to evaluate the utility of both columns: (1.) methylmethyl-, methylethyl-, methylpropyl and methylbutyl-; (2.) ethylmethyl-, ethylethyl-, and ethylpropyl-; (3.) propylmethyl-, propylpropyl-, and propylbutyl-; and (4.) butylmethyl-, butylethyl-, butylpropyl-, and butylbutyl nitrosamines.

The results show that both columns performed well in separating the nitrosamines in each group, with the C₁₈ column requiring a higher percentage of organic modifier (methanol) than the β-cyclodextrin column. The β-cyclodextrin column was superior in separating all the E to Z isomers of short chain alkyl nitrosamines, while the C₁₈ column was superior in separating long alkyl chain nitrosamines and their E and Z isomers.

It, was also found that, the longer the alkyl chain the longer the retention time, while nitrosamines having the same number of carbons, for example ethylbutyl-and propylpropyleluted at virtually the same time, using both columns.     

Mesomorphic behaviour of praseodymium(III) alkanoates

In this paper, we describe the synthesis, characterization and thermal behaviour of praseodymium(III) alkanoates. The compounds have the stoichiometry [Pr(C _x H_2x+1COO)₃], where x = 5-19, and were characterized by elemental analysis and infrared spectroscopy. The thermal behaviour was investigated by hot-stage polarizing optical microscopy, DSC and high temperature X-ray diffraction. A highly viscous mesophase M and a smectic A phase were observed for the shorter chain compounds (x = 5-8), whereas only a smectic A phase was observed for the longer chain compounds of this type of metallomesogens. The chain length has a pronounced effect on the transition temperatures.     

Interfacial and Thermodynamic Properties of Formation of Water‐in‐Oil Microemulsions with Surfactants (SDS and CTAB) and Cosurfactants (n‐Alkanols C5–C9)

The interfacial and thermodynamic properties of water‐in‐oil microemulsion systems consisting of water, isopropyl myristate, n‐alkanol, and surfactant have been investigated using the method of dilution. The surfactants used were hexadecyl trimethylammonium bromide and sodium dodecylsulfate, and the cosurfactants were n‐alkanols with varying chain length from (C₅–C₉). The distribution of cosurfactant (n‐alkanol) between the interface of water and oil regions at the threshold level of stability as well as the energetics of the transfer of the cosurfactant from the oil to the interfacial region have been examined as a function of varying cosurfactant chain length (C₄–C₉) and temperature. The structural parameters (including dimension, population density and effective water pool radius) of the dispersed water droplets in the oil phase have also been evaluated and correlated with alkanol chain length.     

Determination of C4–C14 carboxylic acids by capillary zone electrophoresis: Application to the identification of diamide degradation products and partitioning studies

Capillary zone electrophoresis (CZE) was investigated for the determination of linear saturated carboxylic acid homologues ranging from C₄ to C₁₄. Separation conditions were optimised to overcome the problems of decreasing solubility and decreasing selectivity between successive homologues with increasing chain length. Separations were performed at 20°C, using a 20 kV separation voltage and a pH 8 electrolyte containing 30% methanol. A suitable chromophore (4-aminobenzoate) was added to ensure indirect UV detection of the analytes. Calibration curves and repeatability were established. Minimum detectable concentrations of 3·10⁻⁶ mol l⁻¹ were achieved. Resolution between successive homologues was better than 2. The electrophoretic mobility of each homologue (n=7–14) was assessed and a quasi-linear relationship between the mobility value and 1/n was observed. The quantitative analysis of a diamide degradation solution was performed and compared to potentiometric results. The CZE method was also applied to the determination of C₇–C₁₄ partitioning between an organic medium containing tributylphosphate in n-dodecane and different basic solutions. Their behaviour was established according to the chain length and the pH of the aqueous phase. For C₁₀–C₁₄ compounds, results were validated by comparison with gas chromatographic analysis of the organic phases.