Synthesis and utilization of alternative chain transfer agent in cobalt catalyzed 1,3-butadiene polymerization reaction to produce cis-polybutadiene rubber

The cyclodimerization of 1,3-butadiene was performed to synthesize 1,5-cyclooctadiene by using nickel-phosphite based catalyst system. The optimization of cyclodimerization reaction was done to achieve up to 80% selectivity towards 1,5-cyclooctadiene. 1,5-Cyclooctadiene, thus synthesized, was subsequently employed as a chain transfer agent (CTA) for controlling the molecular weight (M.W.) of cis-polybutadiene rubber (BR) in cobalt-complex catalyzed 1,3-butadiene polymerization reaction. The M.W. of BR was reduced from 6.7 to 1.88 × 10⁵ g/mol by escalating the concentration of 1,5-cyclooctadiene from 0% to 0.5% with respect to 1,3-butadiene (monomer) concentration. Similar reducing trend was observed for the Mooney viscosity and gel content of BR with increasing 1,5-cyclooctadiene concentration. The efficacy of 1,5-cyclooctadiene as a CTA for 1,3-butadiene polymerization reaction was further explored by conducting polymerization reaction in various solvents and at higher monomer conversion (∼70%). The effect of 4-vinyl cyclohexene, which was a dominant byproduct during cyclodimerization of 1,3-butadiene, was also investigated. The presence of 4-vinyl cyclohexene has shown adverse effect in the polymerization reaction and was not functioning as a chain transfer agent. Finally, a feasibility of replacement of commercially used gaseous CTA, 1,2-butadiene, by in-house synthesized liquid CTA, 1,5-cyclooctadiene, was also investigated.     

Rheology and interdiffusion in miscible blends of a low molar mass liquid crystal and bisphenol A–polycarbonate

The melt rheology of blends of a low molar mass liquid crystal (LC) blended with bisphenol A–polycarbonate (PC), and the self‐diffusion of the polycarbonate in the blends are reported. Results of small angle light scattering indicate that the LC is miscible in the mixture for weight fraction of LC less than 6%. The rheological properties of the blended sample within the miscible regime of the blends vary significantly with LC content. Although at low shear rates, the viscosity is similar to that of the pure polycarbonate, at high shear rates the curves show three regions of behavior, as has been described previously for pure LCs. The diffusion coefficient was obtained from interdiffusion studies using nuclear reaction analysis of bilayer films. An addition of only 1 wt % LC to the polycarbonate significantly increased the diffusion coefficient, but at higher concentration the converse was found. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2187–2195, 2007     

Catalytic Chain Transfer Copolymerization of Propylene Oxide and CO2 using Zinc Glutarate Catalyst

Oligo and poly(propylene ether carbonate)-polyols with molecular weights from 0.8 to over 50 kg/mol and with 60–92 mol % carbonate linkages were synthesized by chain transfer copolymerization of carbon dioxide (CO₂) and propylene oxide (PO) mediated by zinc glutarate. Online-monitoring of the polymerization revealed that the CTA controlled copolymerization has an induction time which is resulting from reversible catalyst deactivation by the CTA. Latter is neutralized after the first monomer additions. The outcome of the chain transfer reaction is a function of the carbonate content, i. e. CO₂ pressure, most likely on account of differences in mobility (diffusion) of the various polymers. Melt viscosities of poly(ether carbonate)diols with a carbonate content between 60 and 92 mol % are reported as function of the molecular weight, showing that the mobility is higher when the ether content is higher. The procedure of PO/CO₂ catalytic chain copolymerization allows tailoring the glass temperature and viscosity.     

LC Separation and Quantification of Tocopheryl Polyethylene Glycol Succinate and Tocopheryl Acid Succinate in TPGS Reaction Mixture

An analytical method was proposed for the determination of d-α-tocopheryl polyethylene glycol 1,000 succinate (TPGS 1000) and d-α-tocopheryl acid succinate (TAS) in TPGS reaction mixture with a simple and inexpensive reversed-phase liquid chromatographic method. The LC separation was carried out on a C18 analytical column with UV detection at 284 nm using acetonitrile and water (90:10, v/v) with 0.5% acetic acid (pH 3.73) at a flow rate of 1.5 mL min^?1. The average recoveries of TPGS were between 95.41 and 96.82%, while those of TAS were between 96.69 and 102.39%. Within-day and day-to-day relative standard deviations of TPGS were less than 0.23 and 0.29%, while those of TAS were less than 0.17 and 0.27%. The content of TPGS was determined in terms of the hydrolyzed α-tocopherol. The alkaline hydrolysis process demonstrated high α-tocopherol recoveries between 98.78 and 103.05%. This method has been applied successfully to the accurate determination of TAS and TPGS in highly complex reaction mixture to monitor the reaction process progress.     

Side‐chain functionalized liquid crystalline polymers and blends, 2. Phase behavior of comb‐shaped liquid crystalline ionomers containing ions of alkaline metals

An effective way to synthesize liquid crystalline ionomers by an exchange reaction between the acid groups of functionalized LC polymers and a metal acetate was examined. A number of LC ionomers containing ions of the alkaline metals Na and Rb (1.2–18.3 mol‐%) were obtained. The introduction of small amounts (1.2–5 mol‐%) of metal ions into a functionalized LC polymer matrix leads to significant changes in the phase state of copolymers – the nematic phase is replaced by a SmA phase; an increase of the content of alkaline metal ions causes linear growth of clearing temperatures. The influence of the nature of the metal ions on the phase behavior of LC ionomers was determined. To describe the peculiarities of the LC ionomers' phase behavior a model based on the assumption that an ion multiplet is formed was proposed. Here, the rigidity of the functionalized LC copolymer chains used as a matrix for the preparation of LC ionomers was taken into consideration.     

Evaluation of two liquid chromatography/tandem mass spectrometry platforms for quantification of monensin in animal feed and milk

Monensin is an anticoccidial drug that has been used as an additive in medicated feed. The United States Food and Drug Administration (USFDA) has included monensin in the national surveillance schemes for residues in foodstuff. In this study, two simple, selective and rapid methods were developed to determine monensin content in animal feed and milk. The methods enabled the detection of monensin residues as low as 1 ppb. Moreover, the two methods were used as models to compare two common liquid chromatography/tandem mass spectrometry (LC/MS/MS) platforms; an LC linear ion trap (LC/LIT) and an LC triple quadrupole (LC/QqQ). The two instrument platforms were evaluated for their matrix effect dependence, precision and accuracy. The LC/QqQ presented a lower limit of detection and limit of quantitation (LOD and LOQ) and showed less matrix dependence as compared to the LC/LIT. The LC/QqQ instrument also demonstrated a better intermediate precision. For example, the intermediate precision standard deviation calculated for 27 analyses across three days was 4% and 11% for LC/QqQ and LC/LIT, respectively. Overall, the LC/QqQ represents a better choice for analysis of monensin with respect to LOD, LOQ, matrix interference and precision. Copyright © 2010 John Wiley & Sons, Ltd.     

尼龙6/液晶聚合物共混体系中化学反应对体系热行为及形貌的影响

采用漫反射红外光谱法(DRIFT)和示差扫描量热法(DSC)研究了2种不同特性黏数的尼龙6与3种液晶聚合物(Vectra A950、Vectra B950和Rodrun LC5000)之间的酯-酰胺交换反应.DRIFT测试证实了尼龙6与LC5000之间存在化学反应.DSC分析表明,酯-酰胺交换反应使体系中尼龙6的熔点下降、结晶度降低.增加反应时间和增大共混体系中液晶聚合物的含量有利于酯-酰胺交换反应的发生.与Vectra A950和Vectra B950相比,分子链柔性较强的Rodrun LC5000与尼龙6之间的化学反应更容易进行.扫描电子显微镜(SEM)观察表明,随着共混时间的延长,分散相形貌由球状粒子发展为短棒状纤维,乃至最终形成直径更细的微纤结构.     

三醋酸纤维素膜辐射可控接枝甲基丙烯酸缩水甘油酯及其性能

三醋酸纤维素(CTA)是一种高强度的天然高分子衍生物,对其进行表面接枝改性将扩展其在物质分离、吸附、检测等领域的广泛应用,但是化学接枝改性CTA比较困难。 本文结合辐射引发接枝和可逆加成-断裂链转移(RAFT)聚合方法,成功地在CTA膜表面可控接枝了聚甲基丙烯酸缩水甘油酯(PGMA)。 研究了吸收剂量、单体GMA质量分数和RAFT试剂含量等因素对接枝率的影响,采用傅里叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)和接触角技术手段对CTA膜接枝前后的结构、形貌和表面性质进行了表征。 实验结果表明,为了得到较高的接枝率,同时又保持较好的形貌,合适的条件为:吸收剂量为10~12 kGy,GMA质量分数为30%,RAFT试剂与GMA的物质的量比为1：400;在不同条件下得到的最高接枝率为41%,接枝聚合物相对分子质量分布最低为1.33。 此外,接枝PGMA后的CTA膜疏水性增加。 该工作提供了可控接枝CTA的简便方法,与传统辐射接枝相比,RAFT辅助辐射接枝反应更加可控,得到的PGMA接枝链更加均匀,有利于根据实际应用来控制接枝率和进行后续的功能修饰。     

Kinetics of the seeded semicontinuous emulsion copolymerization of methyl methacrylate and butyl acrylate

The effect of a chain‐transfer agent (CTA) on the kinetics and molecular weight distribution of the methyl methacrylate/butyl acrylate semicontinuous emulsion polymerization was investigated. The dodecanethiol had a slight effect on the reaction rate but significantly affected the secondary nucleation. The effect of the CTA concentration on the gel formation and the effect of the reaction conditions on the mass‐transfer limitations of the CTA are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 367–375, 2000     

胆甾侧链聚硅氧烷高分子液晶的合成与相行为研究

本工作利用双键与Si-H键的加成反应合成了以丙烯酸胆甾醇酯为侧链的硅氧烷梳状聚合物液晶ECS.聚合物的结构得到了核磁与红外分析的证明.偏光显微镜和DSC对ECS的相态转变研究表明,ECS在一定的温度范围内能够形成液晶相,液晶相的存在范围与聚合物的结构密切相关.     

Separation and identification of organic acid-coenzyme A thioesters using liquid chromatography/electrospray ionization-mass spectrometry

A method has been developed for the direct determination of coenzyme A (CoA) and organic acid-CoA thioesters in mixtures using directly combined liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). Mixtures of CoA and organic acid-CoA thioesters were analyzed by LC/ESI-MS with detection of protonated molecular ions and characteristic fragment ions for each compound. The identities of the CoA-thioesters were established based on LC retention times and simultaneously recorded mass spectra. Monitoring of the CoA specific fragment ion at m/z 428 throughout the chromatogram provides a unique fingerprint for CoA content in the samples that corroborates the identification of organic acid-CoA thioesters in the mixtures. Furthermore, fragment ions arising from the ester linkage portion of the molecule allow unambiguous identification of the CoA esters in the samples. A second LC elution system was developed that allows the simultaneous separation and identification of 2-hydroxypropionyl-CoA (lactyl-CoA) and 3-hydroxypropionyl CoA (3HP-CoA), which have the same mass and identical MS fragmentation behavior. The utility of LC/ESI-MS employing this elution system is demonstrated by the determination of 3HP-CoA and lactyl-CoA (converted to CoA-thioesters from their corresponding free acids using CoA-transferase) in fermentation broths from Escherichia coli strains engineered for the production of 3-hydroxypropionic acid (3HP). External calibration employing a purified 3HP-CoA standard allowed indirect quantification of 3HP content in the broth with a precision of 1% (RSD). The feasibility of extending the method described above to perform LC/selected reaction monitoring-tandem mass spectrometry for direct determination of organic acid-CoA thioesters in cells was also demonstrated.     

Effects of monomer structures on the evolution of liquid–crystal texture and crystallization during thin-film polymerization

We investigated in situ the effects of monomer structures on the formation and evolution of liquid–crystal texture and crystallization during thin-film polymerization of a series of liquid–crystalline and crystalline polymers. The monomers used in this study consisted of 2,6-acetoxynaphthoic acid (ANA), p-acetoxybenzoic acid (ABA), acetoxy acetanilide (AAA), and isophthalic acid (IA). The polycondensation reactions were conducted on the heating stage of a polarizing microscope. The formation of liquid crystallinity was found to be strongly dependent on the straight-monomer structures of ANA and ABA and their percentages as well as the reaction temperature. For the ANA/AAA/IA and ABA/AAA/IA reaction systems, the critical straight-monomer content (ANA or ABA) existed to form the liquid–crystalline (LC) state. Interestingly, the critical content to form liquid crystallinity decreased with an increase in the reaction temperature. Above the critical content, the appearance of a defective LC phase and the annihilation of disclinations were observed during the polycondensation reactions. The number of defects decreased with increasing reaction time through annihilation. The annihilation rate increased whereas the defect density decreased with increasing straight-monomer content. For the same molar ratio, the reaction system containing ANA had a faster annihilation rate than that containing ABA. Below the critical content, crystalline polymers were formed. Nucleation and crystal growth were observed during the reactions, and the rate of crystal growth decreased with increasing ANA or ABA content. For the systems having the same molar ratio of ANA or ABA, the ANA/AAA/IA system had a higher tendency to yield the LC phase than the ABA/AAA/IA system because ANA has a longer mesogenic unit. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3084–3096, 1999     

New Cyclic Dimers of Cholic Acid

Two new cyclic dimers of cholic acid were obtained in the reaction of 3-O-acetyl methyl cholate with oxalyl chloride. The oxalates bound the cholate subunits side-to-side as a result of acylation of 7 and 12 OH groups in the substrate. The selective deprotection of hydroxy groups at C-3 and C-24 proved to be rather difficult and led to various products depending on the reaction conditions.     

Improvements in morphological and electro‐optical properties of polymer‐dispersed liquid crystal grating using a highly fluorine‐substituted acrylate monomer

To improve the morphological and electro‐optical properties of a polymer‐dispersed liquid crystal (PDLC) grating, a type of highly fluorine‐substituted acrylate monomer was added to the prepolymer mixture. The morphologies of the PDLC gratings were investigated using atom force microscopy and scanning electron microscopy. The grating had a very clear polymer/LC interface after addition of 3.9 wt % of fluorine‐substituted monomer. The LC droplets in this case were much larger than the sample without fluorinated monomer. This phenomenon indicated that an almost complete phase separation had occurred. However, as the content of fluorine‐substituted monomer increased, the morphologies of gratings became less defined and the volumes of LC droplets were smaller. The diffraction efficiency (DE) decreased with increasing of fluoride content and the V ₉₀ increased simultaneously, which may be ascribed to the blurry interface and the small LC droplets. The highest DE (90%) and lowest V ₉₀ (70 V) were obtained simultaneously under the condition of 3.9 wt % fluoride added in the prepolymer. In addition, it was also found that the fluorine‐substituted monomer may disorder the alignment of LCs in the grating.     

热致液晶（LC70）／PET共混物的结构与性能

采用ＷＡＸＤ、ＤＳＣ、ＰＯＭ、ＳＥＭ和力学测试方法研究了ＬＣ７０／ＰＥＴ原位复合材料的结构与性能。结果表明,当ＬＣ７０／ＰＥＴ＜２０％时,ＬＣ７０对ＰＥＴ的结晶生长具有一定促进作用;当ＬＣ７０／ＰＥＴ＞３０％时,共混物结晶能力迅速下降,结晶放热和熔融焓明显降低。     

Determination of antitubercular drugs in urine and pharmaceuticals by LC using a gradient flow combined with programmed diode array photometric detection

The simultaneous determination of the antitubercular drugs rifampicin, pyrazinamide, isoniazid and the acetylisoniazid metabolite has been accomplished by LC, using a C-18 analytical column. The assayed drugs are usually administered together in the treatment of tuberculosis. Creatinine was also included in the chromatographic determination, in order to establish the curve of excretion of the drugs in urine. The chromatographic method uses a gradient flow in three steps, in conjunction with a programmed diode array photometric detection. In a 0.02 M potassium dihydrogen phosphate pH 7.0 buffer, a 5% (v/v) content of methanol for 1 min, a 8% (v/v) content of methanol for 3.4 min, and a 75% (v/v) content of methanol for 4 min were used. At 4.5 min, the wavelength value of detection was changed from 254 to 475 nm. Creatinine, acetylisoniazid, isoniazid and pyrazinamide were eluted in the first 4.5 min and rifampicin before 8 min. The method has been satisfactorily applied to the determination of the drugs in urine samples and in pharmaceuticals. The proposed LC method is simple, and a short time, less than 8 min is necessary for compounds elution.     

Analysis of anthocyanin pigments in Lonicera (Caerulea) extracts using chromatographic fractionation followed by microcolumn liquid chromatography-mass spectrometry

Anthocyanins from the fruit Lonicera caerulea L. var. kamtschatica (blueberry honeysuckle, Caprifoliaceae) were studied via (semi)preparative chromatographic fractionation followed by MS and μLC/MS analysis. The extraction procedure was optimized with respect to analytical purposes as well as its potential use for the preparation of nutraceuticals. The highest yield of anthocyanins was obtained using acidified methanol as the extraction medium. A comparable total anthocyanin content was obtained using a mixture of methanol and acetone. However, when Lonicera anthocyanins were in contact with acetone, a condensation reaction occurred to a large extent and related 5-methylpyranoanthocyanins were found. The effect of other extraction media, including ethanol as a "green" solvent, is also discussed. The potential of two fractionation procedures for extract purification differing in their chromatographic selectivity and scale was studied (i.e. using a Sephadex LH-20 gel column and a reversed phase). Fractions obtained by both procedures were used for a detailed analysis. MS and μLC/MS(2) methods were used for monitoring anthocyanin and 5-methylpyranoderivatives content as well as identifying less common and more complex dyes (dimer of cyanidin-3-hexoside, cyanidin-ethyl-catechin-hexosides, etc.). These more complex dyes are most likely formed during fruit treatment.     

Effect of catalysts on thin‐film polymerization of thermotropic liquid crystalline copolyester

Using a novel thin‐film polymerization technique, we have investigated in situ uncatalyzed and catalyzed polycondensation reaction systems for 73/27 (mol ratio) poly(p‐oxybenzoate/2,6‐oxynaphthoate) [P(OBA/ONA)] thermotropic liquid crystalline copolyester. We have also determined the effect of catalysts on the kinetics and morphological changes of the reactions. Because the thin‐film polymerization is conducted on the heating stage and the morphology is observed in situ by a polarizing microscope, we can directly observe and determine the accurate onset time for LC phase generation. The number‐average degree of polymerization (DP) at the onset of this morphological change decreases with decreasing reaction temperature in the range of 230–290 °C. The LC phase may form at a DP as low as 2 at 230 °C. Most importantly and surprisingly, the reaction rate constant obtained from the thin‐film polymerization is much greater (20–30 times) than the previous reported value obtained from the bulk polymerization reaction because the release of acetic acid in the former is much easier and quicker than in the latter. Clearly, the thin‐film polymerization may be a better and accurate technique to observe the approximately inherent properties of polymerization kinetics than the traditional bulk polymerization reaction. Three kinds of catalysts, namely, sodium acetate, calcium acetate, and antimony oxide, have been studied. Sodium acetate has obvious acceleration effect on the reaction. Reaction rate constant increases almost proportionally to the catalyst content in the low catalyst content range, and activation energy slightly decreases with an increase in sodium acetate percentage. Calcium acetate has a higher catalytic effect than sodium acetate when the catalyst content is high, but the trend reverses when the catalyst content is low. Polymerization with high content of calcium acetate produces LCP with undesirable morphology because it suppresses the coalescence process among LC domains. Antimony oxide is a polymerization inhibitor for this reaction. It slows down the reaction, but does not alter the sequence of the morphological changes during the polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1257–1269, 2000     

Synthesis of Poly(methyl acrylate) Grafted onto Silica Particles by Z-supported RAFT Polymerization

RAFT polymerization of methyl acrylate (MA) mediated by silica-supported 3-(methoxycarbonyl-phenyl-methylsulfanylthiocarbonylsulfanyl) propionic acid (Si- MPPA) and 3-(benzylsulfanylthiocarbonylsulfanyl) propionic acid (Si-BSPA) was investigated. The molecular weight and polydispersity of grafted polymeric chains and the grafted chain transfer agent (CTA) efficiency (G_e) were strongly dependent on the types and loading of Si-CTAs and free CTA used in solution. Under similar reaction conditions, the graft polymerization mediated by Si-MPPA was better controlled than that using Si-BSPA. The introduction of a free CTA in solution during Si-MPPA mediated polymerization could significantly decrease the polydispersity of free and grafted polymeric chains and enhance the grafted CTA efficiency, and longer polymeric chains could be grafted onto silica support when Si-MPPA with a higher CTA loading was used to mediate the polymerization. In all cases, the RAFT polymerization using 2-(2-cyanopropyl) dithiobenzoate (CPDB) as a free CTA could afford well-defined grafted PMA and significantly increased G_e value, while the polymerization rate was also decreased.     

Identification and Recovery of an Asymmetric Calix[4]arene Tetranitrile Derivative using Liquid Chromatography and Mass Spectrometry

A simple analytical liquid chromatography mass spectrometry (LC-MS) method and associated instrumentation has been adapted for use by the organic chemist to yield milligram quantities of target compound from a reaction mixture. Calix[4]arene 3 was identified as representing 51% of total peak area of a reaction mixture containing no less than 10 components, using LC-MS. This peak corresponded to a mass of 878.8, equivalent to a complex of 3 and an ammonium cation. Molecular models further rationalize this observation by showing that the asymmetric binding cavity of 3 is suitable for binding tetrahedral guests such as the ammonium ion. By scaling up the LC method, using analytical instrumentation, 55?mg of 98% pure 3 was isolated with a recovery yield of 90% in 1?h. The current method represents a powerful and easily adapted tool for monitoring a challenging synthesis that combines identification, efficient separation and partial characterization for reaction mixture components using readily available instrumentation and methods.