Cationic oligomerization of 1-hexene catalyzed by EtAlCl2–chloroacetic acid complexes

Lower oligomers (dimer to tetramer) of 1-hexene were obtained in high yield (65 wt %) with a new cationic complex catalyst, EtAlCl₂? CCl₃CO₂H, in n-hexane at 70°C, trimer being the major product. A strong oxo acid, CF₃SO₃H, yielded very similar products under the same conditions. Characteristics of the 1-hexene oligomerization by these two catalysts were the high selectivity for dimers to tetramers and the absence of cracking of the product. In contrast, EtAlCl₂ or AlCl₃ alone led to oligomers with a higher molecular weight (～10³) and a broad molecular weight distribution, the structure of which was very complicated because of extensive cracking of products. A series of EtAlCl₂? chloroacetic acid (CCl_nH₃–nCO₂H, n = 0–3) complexes were also examined as catalysts. The yield of dimer to tetramer increased with increasing acidity of the chloroacetic acids. The mechanism of the 1-hexene oligomerization with these complex catalysts was discussed on the basis of the structure of product oligomers.     

Determination of positional distribution of butyryl groups in milkfat triacylglycerols,triacylglycerol mixtures,and isolated positional isomers of triacylglycerols by gas chromatography and1H nuclear magnetic resonance spectroscopy

Positional isomers (1-butyryl-2X-3Y-rac-glycerol and 2-butyryl-1X-3Y-rac-glycerol;X,Y=long-chain acyls) of saturated triacylglycerols (TAG) with 34 and 40 acyl carbons were shown to separate in two chromatographic peaks on immobilized phenyl(65%) methylsilicone column by gas-liquid chromatography, and on reversed-phase ODS-1 column by high-performance liquid chromatography. The analysis of 500-MHz¹H nuclear magnetic resonance (NMR) spectra showed distinct differences between 2-butyryl-1X-3Y-rac-glycerol and 1-butyryl-2X-3Y-rac-glycerol isomers in the resonance signals of methylene and methine protons of glycerol backbone, and carbon-2 methylene of acyl groups, and methyl protons of butyryl group. The¹H NMR spectra of three interesterified mixtures of three monoacid TAG containing saturated butyrate and caproate TAG and unsaturated butyrate TAG showed that triplets of methyl protons of butyryl groups atsn-1(3)- andsn-2-positions in saturated and unsaturated TAG had similar chemical shifts and that the chemical shift of caproyl methyl protons was different from those of butyryl methyl protons. The positional distribution of butyryl groups in isolated positional isomers of butyrate TAG, interesterified TAG mixtures, and natural and interesterified butteroil can be determined by integration of these signals.     

Model studies and the ADMET polymerization of soybean oil

Grubbs' ruthenium catalyst 2 has been employed in model studies of the acyclic diene metathesis (ADMET) polymerization of soybean oil. In the presence of 0.1 mol% of catalyst 2, the ADMET polymerization of ethylene glycol dioleate afforded the isomerized (E)-dioleate (27%), dimer (18%), trimer (13%), tetramer (7%), pentamer (5%), hexamer (4%), heptamer (4%), and 9-octadecene (21%). Only a trace of any intramolecular cyclized product was formed. Under the same conditions, glycerol trioleate underwent ADMET polymerization to produce dimer, trimer, tetramer, pentamer, and monocyclic oligomers, with monocyclic oligomers predominating. The high number of repeat units in the monocyclic oligomers (n≅6, 10, and 21) in dicates that cross-linking occurs readily in this process. Based on our model system studies, we have examined the ADMET polymerization of soybean oil and succeeded in producing polymeric materials ranging from sticky oils to rubbers.     

Influence of reduction-oxidation synthesis conditions on the nature of color centers in silicate glass doped with selenium

Silicate glasses doped with elemental selenium and compounds affecting its oxidation state are studied using optical spectroscopy (absorption, resonance Raman scattering, luminescence). The absorption spectra of the synthesized glasses contain three bands with maxima at energies of 1.64, 2.47, and 3.5 eV. The band observed at 2.47 eV is identified in the resonance Raman spectrum from the appearance of the vibrational mode at 323 cm⁻¹, which belongs to the Se₂⁻ dimer. The other two bands are supposedly assigned to the Se₃⁻ trimer (1.64 eV) and the Se₂ dimer (3.5 eV) according to the data available in the literature for the crystal structures. It is shown that the relative content of these centers and their related coloration of glasses are determined by the reduction-oxidation synthesis conditions. Original Russian Text ? A.A. Lipovskii, V.G. Melekhin, V.D. Petrikov, B.V. Tatarintsev, 2008, published in Fizika i Khimiya Stekla.     

Cure and reaction kinetics of an anhydride‐cured epoxy resin catalyzed by N‐benzylpyrazinium salts using near‐infrared spectroscopy

The cure behavior and the reaction kinetics of an anhydride‐cured epoxy resin catalyzed by cationic thermal latent initiator, N‐benzylpyrazinium salts, have been investigated by a near‐infrared (NIR) spectroscopy. The spectral changes are interpreted in terms of the mechanism of cure. NIR absorption bands are due to protons connected to carbon, nitrogen, and oxygen. In this work, the homogeneous model system involves a simple addition reaction mechanism leading to an exothermic reaction between epoxide and anhydride activated groups. A comprehensive account of the origin, location, and shifts during reaction of all major NIR absorption peaks in the spectral range from 4000 to 7100 cm^?1 is provided. The extent of reaction is calculated from NIR absorption band at 4530 cm^?1, which depends on epoxide concentration. The utility of NIR spectroscopy to study the kinetics of epoxy cure reaction has been established. Consequently, absorbencies in the NIR spectra suitable for quantitative studies of epoxy resin reaction kinetics have been identified.     

Preparation and properties of photocurable unsaturated oligoester acrylourethanes

Syntheses of several photocurable resins and their properties before and after photocuring are investigated. Unsaturated oligoester acrylourethanes (IIIa–IIId) are prepared by addition reaction between four types of hydroxy-terminate unsaturated oligoesters (Ia–Id) and intermediate of adduct II. The former is prepared by addition-condensation reaction of glycols and maleic anhydride, while the latter is prepared from 2,4-TDI and equivalent HEMA by addition reaction in the presence of stannous octoate with THF as solvent. From the decrease of NCOs characteristic absorption peak at 2250 cm^?1 of IR spectrum, the conversions of the reaction of 2,4-TDI with HEMA and hydroxy-terminated unsaturated oligoesters were calculated. The unsaturated photocurable resins are compared with saturated oligomers (obtained by replacing maleic anhydride with succinic anhydride) with regard to curing rates and mechanical properties. Properties of pure oligomers are determined both before and after hardening. If added with reactive monomers, the oligomers thus cured are found to possess better properties than otherwise. Among the monomers, HEMA proves to be especially helpful in the increase of mechanical properties. Above all, combined use of IIIb oligomer and HEMA serves the best purpose for metal coating.     

Raman Spectrum of Iodine Pentafluoride: Evidence for Polymerization in the Liquid State

Raman spectra of iodine pentafluoride have been measured for the gas as well as for the liquid as a function of temperature. The intense polarized band which appears in the room temperature spectra of the liquid at 697 cm^?1 and a weaker, previously unreported, band at 218 cm^?1 are absent both from the gas spectra and from the elevated temperature spectra of the liquid. This indicates that these bands arise from the presence of polymers in the liquid state rather than from Fermi resonance.     

Synthesis and characterization of cardanol‐grafted natural rubber—The solution technique

Cardanol, a by‐product of the cashew industry, has been recently proven to be a multifunctional additive (MFA) in rubbers. It is expected that grafting of cardanol onto natural rubber (NR) would impart inherent MFA characteristics to the rubber. Grafting has been carried out in solution using toluene as the solvent and a peroxide initiator. Optimized conditions of grafting reaction could be arrived at using a statistical tool namely orthogonal array testing strategy, keeping the maximum percentage of grafting as the selection criteria. Further studies were conducted to study the influence of monomer concentration and initiator concentrations. The effect of the reaction temperature and reaction time were also investigated. Characterization of grafted rubber was carried out with the help of infrared spectroscopy, nuclear magnetic resonance spectroscopy and thermal analysis. IR spectrum of cardanol exhibited the characteristic peak of cardanol at 3356 cm^?1. Percent grafting (PG) of cardanol onto NR was determined by residual weight method. PG increased with increasing cardanol quantity reached an optimum and then decreased. The increase in reaction time and reaction temperature also caused increasing levels of the grafted cardanol. However, PG continuously increased with increasing initiator concentrations. Differential scanning calorimetry studies of the grafted NR showed a lower glass transition temperature than that of the raw NR, which is indicative of the plasticization effect of cardanol. The thermogravimetric analysis showed a higher thermo oxidative stability for cardanol‐grafted NR. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Structural changes and crystallization kinetics of polylactide under CO2 investigated using high‐pressure Fourier transform infrared spectroscopy

The structural changes and crystallization kinetics of polylactide (PLA) during cold crystallization under CO₂ at 80 °C were studied using in situ high‐pressure Fourier transform infrared (FTIR) spectroscopy. The FTIR spectra show that PLA can crystallize under air and CO₂, and some differences are observed. In the second‐derivative spectra, the 1220 cm^?1 band is only found for PLA crystallized under CO₂, and the tt conformer of PLA crystallized under CO₂ is located at 1749 cm^?1, while that of PLA crystallized under air is located at 1751 cm^?1. From wide‐angle X‐ray diffraction, only the α′‐crystal is observed when PLA is crystallized under air, whereas the α‐crystal appears when crystallized under CO₂. The crystalline‐sensitive bands at 921 and 1458 cm^?1 were used to analyze the crystallization kinetics of PLA. When PLA crystallizes under air, the 1458 cm^?1 band changes faster than the 921 cm^?1 one; when it crystallizes under CO₂, the result reverses. This suggests that CO₂ hinders interchain interactions while promoting the helix conformation. © 2015 Society of Chemical Industry     

Infrared Spectra and Surface Reactions of HCl,DCl and Cl2 Adsorbed on Germanium

Adsorption of HCl, DCl and Cl₂ on high surface area germanium films was studied by means of IR absorption spectra. The films were prepared by high temperature evaporation of germanium in a helium atmosphere. On adsorption of HCl and DCl two main absorptions appeared at 460 cm^?1 and 408 cm^?1 and additional weaker bands at 2050 cm^?1 and 2920 cm^?1 (with HCl) and at 1313 cm^?1 (with DCl). The spectra indicate that both gases undergo dissociation on adsorption. In the case of Cl₂ the bands at 460 cm^?1 and 408 cm^?1 appeared in the spectrum; here again strong evidence exists that dissociative adsorption takes place. Mass spectrometer analysis showed that the desorption product consists mainly of GeCl₄.     

Comparative analysis of different properties of polyhydroxyalkanoates isolated from two different bacterial strains: Alkaliphilus oremlandii OhILAs and recombinant Escherichia coli XL1B

We synthesized poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(3‐HB‐co‐3‐HV)] copolymer having different contents of 3‐hydroxyvalerate (3‐HV) units (16.04, 16.3, 24.95, 25.62, and 16.52 mol % 3‐HV) with different yields of polyhydroxyalkanoates (PHAs) by feeding with different cooking oils and with Alkaliphilus oremlandii OhILAs strain. The PHA production efficiency of the Alkaiphilus strain was compared with that of the control strain, Bacillus cereus. The synthesis of each PHA biopolymer was performed with different toxic spent oils as the sole carbon source in an oil‐in‐water‐based microemulsion medium. We observed that the productivity of the poly(3‐hydroxybutyrate) [P(3‐HB)] copolymer from the Alkaliphilus strain was higher than those of the PHAs isolated from B. cereus and the Escherichia coli XL1B strain. The synthesized PHA copolymers were characterized by ¹H‐NMR and Fourier transform infrared (FTIR) spectroscopy. In the ¹H‐NMR spectra, a doublet resonance peak at 1.253 ppm of the/ methyl protons of the 3‐hydroxybutyrate (3‐HB) side group and one at 0.894 ppm due to the methyl protons of the 3‐HV side group indicated the presence of 3‐HB and 3‐HV units in the copolymer. The chemical shift values at 1.25 and 2.2 ppm, due to the resonance absorption peaks of the methyl protons and methylene protons, confirmed the synthesis of the P(3‐HB) homopolymer. From the FTIR spectra, a strong C?O stretching frequency in the range of 1745–1727 cm^?1, together with strong C? O stretching bands near 1200 cm^?1 and a strong band near 3400 cm^?1, confirmed the synthesis of P(3‐HB‐co‐3‐HV) and P(3‐HB). Thus, waste cooking oil as a substrate provided an alternate route for the formation of P(3‐HB‐co‐3‐HV) and P(3‐HB) by Alkaliphilus and E. coli strains, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41080.     

壬基酚甲醛低聚物的组成分析

以壬基酚和甲醛为原料,在十二烷基苯磺酸催化下制备得到壬基酚甲醛低聚物。采用高效液相色谱-质谱联用技术,对壬基酚甲醛低聚物进行了组成分析。结果表明,壬基酚甲醛低聚物中含有游离壬基酚、十二烷基苯磺酸、二聚体、三聚体、四聚体、五聚体、六聚体及七聚体。该方法简捷可行,可对壬基酚甲醛低聚物的质量性能进行有效监控。     

Side effects in the application of polyamide 6 barrier materials for fuel tanks

To reduce the pollution of air by minimizing evaporative emissions from fuel tanks, new plastic fuel tanks made of materials with excellent barrier properties have to be developed. Single‐layer polyamide 6 tanks are one option to meet the requested low‐hydrocarbon permeation rates for motorcycle vehicle tanks. Recently, some problems with respect to deposits in polyamide 6 tanks, blocked nozzles, tubing, and gasoline filters were observed. Thus, samples (precipitates) were taken from unused tanks after conditioning as well as of used tanks and filters after being in contact with gasoline for some time. By investigating the precipitates and deposits by means of infrared (IR) spectroscopy, the main constituents were identified to be cyclic caprolactam oligomers. Additional investigations on the extracted samples by mass spectroscopy allowed us to attribute specific features of the IR spectra to the individual cyclic oligomers (dimer, trimer, and tetramer). In addition, we could show that the crystalline precipitates and deposits in the fuel systems of used vehicles consist of mixtures of the cyclic dimer, trimer, tetramer, and even pentamer of caprolactam with varying contributions of the individual oligomers in dependence of the history of the part. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of chemically modified wood fibers using FTIR spectroscopy for biocomposites

Chemical modifications of wood fibers (Lignocel® C120) were performed for biocomposite applications, and chemically modified wood fibers were analyzed by FTIR spectroscopy. NaOH treatment showed band shifts from Cell‐I to Cell‐II in FTIR spectra from 2902 cm^?1, 1425 cm^?1, 1163 cm^?1, 983 cm^?1, and 897 cm^?1 to 2894 cm^?1, 1420 cm^?1, 1161 cm^?1, 993 cm^?1, and 895 cm^?1 and the change in peak height at 1111 cm^?1 and 1059 cm^?1 assigned for Cell‐I structure. Silane treatment showed peak changes at 1200 cm^?1 assigned as Si? O? C band, at 765 cm^?1 assigned as Si? C symmetric stretching bond, at 700 cm^?1 assigned as Si? O? Si symmetric stretching, and at 465 cm^?1 assigned as Si? O? C asymmetric bending. Benzoyl treatment resulted in an increase in the carbonyl stretching absorption at 1723 cm^?1 and in band characteristics of aromatic rings (1604 cm^?1 and 710 cm^?1) and a strong absorption at 1272 cm^?1 for C? O band in aromatic ring. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rational Design of Domain‐Swapping‐Based c‐Type Cytochrome Heterodimers by Using Chimeric Proteins

The design of protein oligomers with multiple active sites has been gaining interest, owing to their potential use for biomaterials, which has encouraged researchers to develop a new design method. Three‐dimensional domain swapping is the unique phenomenon in which protein molecules exchange the same structural region between each other. Herein, to construct oligomeric heme proteins with different active sites by utilizing domain swapping, two c‐type cytochrome‐based chimeric proteins have been constructed and the domains swapped. According to X‐ray crystallographic analysis, the two chimeric proteins formed a domain‐swapped dimer with two His/Met coordinated hemes. By mutating the heme coordination structure of one of the two chimeric proteins, a domainswapped heterodimer with His/Met and His/H₂O coordinated hemes was formed. Binding of an oxygen molecule to the His/H₂O site of the heterodimer was confirmed by resonance Raman spectroscopy, in which the Fe?O₂ stretching band was observed at 580 cm^?1 for the reduced/oxygenated heterodimer (at 554 cm^?1 under an ¹⁸O₂ atmosphere). These results show that domain swapping is a useful method to design multiheme proteins.     

Synthesis and characterization of polyazomethine conducting polymers and oligomers

Conjugated polyazomethine polymers were prepared from the polycondensation of terephthalaldehyde with 4,4′-thiodianiline, and 4,4-thiodibenzaldehyde with 4,4′-thiodianiline, 4,4′-phenylenediamine and benzidine. The polymers showed good stability in air and were soluble in many organic solvents. The electrical conductivities of the undoped and doped (H₂SO₄ and I₂) polymers were studied. Doping the polymers markedly increased their conductivities from 10^?8 ? 10^?11 S cm^?1 (dielectric region) to 10^?3 ? 10^?5 S cm^?1 (semiconducting region). The polymers were characterized by IR spectroscopy, elemental analyses, viscosity measurements and X-ray diffraction. Furthermore, polyazomethine oligomers were prepared and a comparative study of the physical properties of the oligomers and their corresponding polymers was performed. The electrical behavior of the oligomers was studied. It was found that oligomers with a minimum of eight aromatic (Ar) rings gave almost the same electrical conductivities as long-chain polymers.     

Stereochemical effects on the fragmentation in mass spectrometry of stereoregular oligomers of methyl methacrylate

Summary The effects of stereochemical structure of MMA oligomers on the fragmentation during ionization process in electron-impact ionization and chemical ionization mass spectrometry were studied using the oligomers prepared by stereospecific living oligomerization. The MMA oligomers having t-C₄H₉-group at the left end and methine proton at the right end showed strong tacticity dependence in their fragmentation process. Fragmentation of MMA tetramer having one head-to-head linkage in the middle of the chain was also studied.     

Synthesis and properties of oxetane monomers and oligomers with electro‐active pendent groups

BACKGROUND: Monomers and polymers carrying pendent electro‐active fragments are widely studied due to their application in various optoelectronic devices. Monomers containing triphenylamino, triphenyldiamino and carbazol‐9‐yl fragments with vinyl, epoxy or acryl functional groups are mostly used. The synthesized materials are used for preparation of hole transport layers as well as host materials for electrophosphorescent light‐emitting diodes. Much fewer presentations are reported on the preparation of monomers containing other electro‐active or functional groups. RESULTS: Here we describe oxetane monomers and their oligomers containing various electro‐active pendent groups. The weight‐average molecular weights of the oligomers are in the range 1420–3250 g mol^?1 with a molecular weight distribution of 1.7–4.1. The electron photoemission spectra of amorphous layers of the compounds established ionization potentials of 5.55–5.85 eV. Room temperature hole drift mobility in the layers of some oligomers exceeds 10^?7 cm² V^?1 s^?1 at high electric fields. CONCLUSION: The synthesized oligomers exhibit promising thermal and film‐forming properties. Amorphous layers of some of the materials demonstrate suitable ionization potentials and sufficient hole transport properties for their application in optoelectronic devices. Copyright © 2008 Society of Chemical Industry     

Model processing agents for rubber manufacturing

Summary Oligomers with different aromatic substituents (oligostyrenes, oligo-p-ethylstyrenes, oligo-p-methoxystyrenes and oligo-1-vinylnaphthalenes) were synthesized by living anionic polymerization using sec-butyllithium as initiator. Number average degrees of polymerization were varied between 2 and 16 and narrow homologuedistributions were obtained. In the case of the benzenic types the isolation into pure homologues from dimers to hexamers was carried out by preparative gel permeation chromatography (GPC). In a polymeranalogous heterogeneous catalytic hydrogenation reaction the aromatic compounds were converted into oligomers with saturated cyclic structures, the initial homologue-distributions not being changed. Characterization of all oligomers was performed by GPC and proton nuclear magnetic resonance (¹H-NMR). In the case of oligostyrenes and oligo-p-ethylstyrenes the occurrence of the characteristic high field shift of the ortho-protons is observed in dependence of the degree of polymerization. Oligo-1-vinylnaphthalenes show three differently shielded aromatic resonance areas.     

Electrosynthesis and characterization of o‐phenylenediamine oligomers

The contribution of electrochemical methods to the development of conducting polymers has been most relevant, although the electropolymerization mechanism has not yet been totally elucidated. The formation of a high‐density oligomeric region in the electrode–solution interface has been clearly established as formed by oligomers with different chain lengths. It has been confirmed that, depending on the variables governing the process (applied potential, electrolysis time, concentration, etc), it is possible to control to some extent the oligomer to be generated. In this present work, the electrosynthesis of oligomers of o‐phenylenediamine is proposed. A saturated solution of the monomer was electrolysed at 0.95 V versus SCE over 1 min, using stainless steel as the working electrode material. Under these conditions, a mixture of the dimer and tetramer, relatively easy to separate by thin layer chromatography, was deposited. The products were characterized by mass spectrometry, UV–vis spectroscopy, elemental analysis and ¹H NMR spectroscopy. This approach allows the synthesis of oligomers in a fast and simple way. In addition, the product is directly obtained on the electrode surface, hence making its separation and purification very straightforward. Copyright © 2004 Society of Chemical Industry