Influence of Polymerization Temperature on Reactivity of 1- and 2.Vinyl Naphthalenes

Reactivity ratios relative to the copolymerizations of 1-vinyl naphthalene and 2-vinyl naphthalene with styrene have been determined at different specific temperatures. In the case of the system 1-vinyl naphthalene-styrene, the Arrhenius plot exhibits a curve when the temperature is above -50°C. This is explained by the depropagation contribution, The value of the enthalpy of polymerization calculated by using the Lowry relation is in satisfactory agreement with that obtained from calorimetric determinations. From activation enthalpies and entropies it appears that the selection of the two monomers by the cation is entropically controlled for 2-vinyl naphthalene and enthalpically controlled for 1-vinyl naphthalene.     

Energy migration and transfer in polymer systems

Theoretical treatments of singlet energy transfer are reviewed with the objective of determining the expressions most relevant for polymeric systems. Observations of singlet energy transfer from 1,3 diphenyl oxazole to 1,4 di[2-(4-methyl 5-phenyl oxazolyl)]-benzene, anthracene and benzophenone confirm that the Förster relationships are valid for dilute solutions of these small molecules. For a polymer donor in which there exists spectral overlap in absorption and emission, there is the possibility of energy migration along the chain. Under these conditions, and where acceptor diffusion may be important, it is found that relationships due to Yokota and Tanimoto are the most useful in both fluid and polymeric environments. Coefficients for migration of singlet energy down chains of poly(N-vinyl carbazole), poly(2-vinyl) naphthalene) and copolymers of N-vinyl carbazole with methyl acrylate have been evaluated. They are consistent with a model in which energy is transferred by a random walk series of Förster interactions between spectroscopically active nearest neighbours.     

Time-resolved spectroscopy of solid poly(1-vinyl naphthalene)following electron beam pulse radiolysis: pulse radiolytic studies on polymers

Transient emission studies following pulse radiolysis of solid poly(1-vinyl naphthalene) show existence of excited monomers and two excimers. Quenching experiments indicate that excimers are not formed directly by recombination of ions but probably by trapping of migrating monomeric excitation in performed traps whose density is approximately one in 10³.     

Excimer dissociation in poly(1-vinyl naphthalene)

Time-resolved fluorescence spectroscopy has been used to probe the formation and decay of excimeric sites in poly(1-vinyl naphthalene) in methylene chloride solution. Contrary to earlier reports, it has been found that reverse dissociation of excimers does occur appreciably at room temperature. Monomer fluorescence decay curves are thus represented by the sum of two exponential terms, and excimer curves by the difference in two exponentials. Lifetimes of 7.43 and 43.1 ns were obtained from the monomer and excimer fluorescence decay data.     

peri-Naphthylenediamines 18. 1,8-Bis(dimethylamino)-4-vinylnaphthalene

The 1-[1,8-bis(dimethylamino)-4-naphthyl[ethyl carbocation generated from the corresponding alcohol in benzene in the presence of Al₂O₃ undergoes elimination according to theE1 mechanism to give previously unknown 1,8-bis(dimethylami no)-4-vinyl naphthalene in a good yield. This compound was also synthesized from 1,8-bis(dimethylamino)-4-formylnaphthalene by the Wittig reaction. Polymerization of the vinylic derivative obtained was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2297–2300, September, 1996.     

Determination of vinyl orientation of mouse neuroglobin by 2D nuclear Overhauser spectroscopy

1H NMR has been used to determine the 2-,4-vinyl orientation of heme active site from oxidized mouse neuroglobin (mNgb).The NOEs between 3-methyl and Hα, Hβ of 2-vinyl, together with the NOEs between 5-methyl and Hα, Hβ of 4-vinyl, allowed the unambiguous determination of trans and cis orientations for the 2- and 4-vinyl groups in the mNgb, respectively.     

Phosphorescence studies of relaxation effects in bulk polymers. I. Depolarization measurements of segmental relaxation in poly(methyl acrylate)

This paper reports the first measurements of macromolecular segmental relaxation times by phosphorescence depolarization. Steady-state phosphorescence polarization experiments were performed on samples of poly(methyl acrylate) incorporating 0.5 wt % copolymerized acenaphthylene or 1-vinyl naphthalene as phosphorescent probes over the temperature range 77 to 310°K. Depolarization of phosphorescence occurs with the onset of segmental motion of the polymer at ca. 278°K. Motion of either probe is characterized by an activation energy of 195 (±5) kJ mole^?1, which is in fair agreement with the mean value of 230 kJ mole^?1 estimated for the segmental relaxation of poly(methyl acrylate) by dielectric and mechanical relaxation techniques. Transient depolarization measurements confirm the absence of probe motion below the glass transition temperature. Phosphorescence intensity and triplet state lifetime data are capable of detection of a second transition in the polymer in accord with observations using more conventional techniques.     

Solid-phase extraction and HPLC determination of 4-vinyl guaiacol and its precursor, ferulic acid, in orange juice.

This study is undertaken to develop a simplified, rapid method to determine both immediate and potential off odors due to 4-vinyl guaiacol and its odorless precursor, ferulic acid, from a single sample preparation and chromatographic analysis. Orange juice sample preparation consists of a simple, C18 solid phase extraction. Utilizing a 5-microns, 25-cm, C18 column, both compounds can be separated within 40 min using a one-step, linear gradient beginning with an aqueous 12% tetrahydrofuran (THF)-5% acetonitrile mixture and ending with 35% aqueous THF. Hesperidin and nariutin have been identified as the compounds that interfered with the ultraviolet (UV) determination of sinapic and caffeic acids. Fluorescence detection with wavelength programming offers optimal sensitivity and selectivity. Recoveries of 4-vinyl guaiacol and ferulic acid range from 90 to 103%. Detection limits are 1 ppm and 5 ppm for ferulic acid and 4-vinyl guaiacol, respectively. Other hydroxycinnamic acids such as coumaric, sinapic, and caffeic acids may also be determined from the same chromatogram.     

The synthesis of azabicyclo[4.2.1]nonenes by the addition of a cyclopropenone to 4-vinyl substituted 1-azetines—isomers of the homotropane nucleus

The conversion of 4-vinyl substituted β-lactams into 4-vinyl substituted 1-azetines and their subsequent reaction with diphenylcyclopropenone (DPP) results in the formation of a highly functionalised 7-azabicyclo[4.2.1]nonene. This heterocyclic system is an isomer of the homotropane (9-azabicyclo[4.2.1]nonene) nucleus, which is the core structure of a class of alkaloid natural products that includes anatoxin-a. The key processes involved are two ring expansions, one of which constitutes a formal [3+2] cycloaddition and the other of which is an unusual aza-Cope (amino-Claisen) [3,3]-sigmatropic rearrangement.     

The preparation of immobilized stationary phase fused silica capillary columns with OV-1701-vinyl deactivation

A new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV-1-vinyl, SE-54, and OV-1701-vinyl. This methodology includes the application of the moderately polar stationary phase OV-1701-vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory-produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV-1701-vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.     

Formation and catalytic activity of spherical composites with surfaces coated with gold nanoparticles

Micelle-supported gold composites with a polystyrene core and a poly(4-vinyl pyridine)/Au shell are synthesized using NaBH(4) to reduce a mixture of micelle and HAuCl(4) in acidic aqueous solution (pH approximately 2). The template micelle with a polystyrene core and a poly(4-vinyl pyridine) shell is formed by self-assembly of block copolymer polystyrene-block-poly(4-vinyl pyridine). The gold nanoparticles coated onto the surfaces of the composites possess an average diameter of about 15 nm. The composites are applied to catalyze the reduction of p-nitrophenol in the presence of NaBH(4), and the results indicate that the kinetic constant of the reaction increases when the composite concentration and the reaction temperature increase. In addition, research results also indicate that composites with high content of gold show higher catalytic activity and higher catalytic efficiency.     

Molecules that mimic Schottky diodes

Self-assembled monolayers of cationic donor-(pi-bridge)-acceptor dyes coupled with anionic donors exhibit asymmetric current-voltage (I-V) characteristics when contacted by Au or PtIr probes. Rectification ratios of 3000 at +/- 1 V are obtained from Au-S-C10H20-A+-pi-D|D-|Au structures in which the cationic moiety is 5-(4-dimethylaminobenzylidene)-5,6,7,8-tetrahydro-isoquinolinium and the counterion is copper phthalocyanine-3,4',4',4'-tetrasulfonate (SAM ). Similar behaviour, with a high rectification ratio of 700-900 at +/- 1 V, is also obtained for the CuPc(SO3-)4 salt of 4-[2-(4-dimethylaminonaphthalen-1-yl)-vinyl]-quinolinium (SAM ). The properties are dependent upon the D-pi-A+ moieties which, for these highly rectifying salts, have sterically locked non-planar structures causing the conjugation to be effectively broken. Its effect on the electrical asymmetry is less spectacular when the cationic species is sterically unhindered: the rectification ratio decreases to 15-70 at +/- 1 V for films of the 4-[2-(4-dimethylaminophenyl)-vinyl]-pyridinium salt (SAM ), which has single-ring substituents on opposite sides of the -CH=CH- bridge and an almost planar D-pi-A+ structure. Rectification ratios from the sterically hindered structures are on a par with electrical asymmetries from metal-insulator-metal (MIM) devices where oxide-induced Schottky barriers dominate the behaviour.     

Synthesis of 1-phenylseleno-1-vinyl and 1-methylseleno-1-vinyl cyclopropanes by formal dehydration of β-hydroxycyclopropyl selenides

Unknown 1-phenylseleno-1-vinyl and 1-methylseleno-1-vinyl cyclopropanes are readily available from β-hydroxycyclopropyl selenides using (carboxysulfamoyl.) triethylammonium hydroxide inner salt methyl ester. Limitations of the method are presented.     

Assignment of stereochemistry to cyclohexenylidenecyanoacetates by 1H NMR spectroscopy

The stereochemistry of various pairs of isomeric 2-cyclohexen-1-ylidenecyanoacetates was assigned using ¹H NMR spectroscopy. The isomers with the γ-methylene or the γ-vinyl protons cis to the carbalkoxy group were found to have the signals of these protons at approximately 0.3 ppm and 1 ppm, respectively, downfield relative to their geometrical isomers or the corresponding 2-cyclohexen-1-ylidenemalononitriles. The observation regarding the γ-vinyl proton proved useful for the assignment of configuration to cyclohex-enylidenecyanoacetates derived form cholest-4-en-3-one. The large and constant downfield shift (c. 1 ppm) of the γ-vinyl proton when cis to the ester group results from the rigid cyclohexenylidenecyanoacetate system, in which the vinylic proton can approach more closely to the magnetically anisotropic ester carbonyl group.     

丙烯酸甲酯/乙烯基吡啶共聚物铑配合物的配体空间结构对甲醇羰基化反应催化性能的影响

针对共聚物配体聚合的随机性及其共聚结构单元的复杂性 ,运用XPS及红外光谱等分析手段 ,探讨了共聚物铑配合物微观结构对催化性能的影响 ;研究了丙烯酸甲酯 2 乙烯基吡啶和丙烯酸甲酯 4 乙烯基吡啶两种共聚物与铑的不同配比的配合物的活性 ,考察了相同配比的共聚物配合物结构单元、温度等因素对消化活性的影响 ,为催化剂结构的合理设计提供了理论参考     

两亲性杂壳聚合物粒子的高效制备及以其作为模板合成金纳米簇合物

将等质量的嵌段聚合物聚乙烯基萘聚丙烯酸和聚氧化乙烯聚丙烯酸（P2VN-b-PAA和PEO-b-PAA）溶解于N,N′-二甲基甲酰胺(DMF)中,加入小分子二元胺（1,2-丙二胺,PDA）,制备出均匀的两亲性杂壳聚合物纳米粒子(MSNPs)。 该粒子以PEO和P2VN混合嵌段为壳层,非共价键交联的PAA嵌段为核,在水相及有机相中均可稳定分散,具有典型的两亲性特点。 扫描电子显微镜和光散射测试结果表明,该杂壳聚合物粒子(MSNPs)的粒径在300 nm左右,分布较均匀,并显示出壳层可塌缩变形的疏松核（软粒子）特征。 以该聚合物粒子(MSNPs)为模板,可以方便制备出金纳米粒子簇合物。     

Transfer constants relative to the cationic polymerization of 1- and 2-vinyl naphthalenes and 3-vinyl phenanthrene

Transfer and termination constants have been determined for the cationic polymerization of 1- and 2-vinyl naphthalenes and 3-vinyl phenanthrene. They have been compared with the values obtained for styrene under the same experimental conditions. Experimental values are in good agreement with theoretical determinations.     

Styrene-containing Phosphine-sulfonate Ligands for Nickel-and Palladium-catalyzed Ethylene Polymerization

A series of phosphine-sulfonate ligands bearing 2-, 3-and 4-vinylphenyl on the phosphorus atom were designed, synthesized,characterized and investigated in Ni-and Pd-catalyzed ethylene polymerization. The structure of the phosphine-sulfonate Pd complex bearing2-vinylphenyl on the phosphorus atom showed 2,1-insertion for the 2-vinyl group. The phosphine-sulfonate Ni complex bearing 2-vinylphenyl resulted in significantly increased thermal stability and polyethylene molecular weights(Mn=3.69×104 g·mol-1 at 80 °C) versus the counterparts bearing 3-/4-vinyl groups as well as previously reported phosphine-sulfonate Ni complexes bearing bulky biaryl substituents.     

Facile synthesis of plasmalogens via Barbier-type reactions of vinyl dioxanes and vinyl dioxolanes with alkyl halides in LiDBB solution

Plasmalogens (i.e. plasmenylcholines or plasmenylethanolamines) are a biologically important class of glycerophospholipids that have been difficult to synthesize due to the presence of an acid and oxidatively labile (Z)-vinyl ether substituent at the sn-1 position and a base-labile sn-2 acyl substituent that easily migrates during silica gel purification. We report two facile synthetic methods for the preparation of racemic plasmenylcholines via a tandem reductive vinyl dioxane/dioxolane ring opening and alkyliodide coupling process that proceeds in a single pot reaction. The key step in the formation of (Z)-vinyl ether precursors for the production of plasmenylcholines is accomplished using LiDBB under Barbier-type conditions to give the corresponding TBDMS-protected 1-O-Z'-vinylglycerol intermediate in moderate yields. This pathway is the most direct synthetic route for the formation of plasmenylcholines to date, requiring a total of six transformations from acrolein and glycerol or solketal as inexpensive starting materials, to generate glycerophosphocholine-type plasmalogens in 4% overall yield.