Kinetic relationships of metal filling of epoxy resin by in situ reduction of silver nitrate

The kinetics of metal filling of ED-20 epoxy oligomer by its action on AgNO₃ in the temperature interval 50–90°C was studied.     

Deconstructing Oligomer Distributions: Discrete Species and Artificial Distributions

The separation of an oligo(methyl acrylate) distribution, obtained from reversible addition–fragmentation chain transfer (RAFT) polymerization, in a discrete (dispersity=1) oligomeric library (degree of polymerization between 1 and 22) is presented. The properties of this library in terms of diffusivity, glass transition temperature, and viscosity are determined, filling a significant knowledge gap associated with these materials. The obtained oligomer library is used to construct artificial oligomer distributions on demand. These artificial oligomer distributions are used to highlight the potential to tailor physical properties of a material, while concomitantly demonstrating the limitations associated with size‐exclusion chromatography analysis of molecular weight and dispersity in particular.     

Improvement in Tensile Strength and Water Repellency of Paper after Treatment with Methyltrimethoxysilane Oligomer Using Titanium Butoxide as a Catalyst

The improvement in the tensile strength and water repellency of paper after treatment with a 2-propanol solution of a methyltrimethoxysilane (MTMS) oligomer was studied using filter paper. Titanium butoxide introduced in the solution as a catalyst effectively reacted with the MTMS oligomer, and a Si–O–Ti bond was generated inside the paper. The tensile strength of the paper was remarkably improved by this treatment of impregnation and polymerization of the MTMS oligomer. It was speculated that the reaction proceeded by consuming water that existed among the cellulose fibers by hydrogen bonding, because there was little difference in the tensile strength between the paper treated in air and the paper treated in a dry box. The methoxy groups in the MTMS oligomer demonstrated their good ability of making a three-dimensional network, and at the same time, the methyl groups in the oligomer showed their excellent water repellency. As a result, the treated paper had a good tensile strength even under wet conditions.     

Synthesis of Citric Acrylate Oligomer and Its In-Situ Reaction with Chrome Tanned Collagen (Hide Powder)

Summary: The purpose of this study was to formulate the new combined system of acrylic and citric acids, which was prepared by free radical polymerization and esterification reaction at the same time to form citric-acrylate CAC oligomer. The presumable chemical structure of this oligomer and the reaction mechanism were investigated by different spectroscopic tools (¹H,¹³C-NMR and ATR-IR), GPC and TGA/DTA. The effect as masking agent of the eco-friendly oligomer (CAC) in the chrome tanning of the collagen and the pickling of the hide was approached by the study of the hydrothermal and mechanical properties of in-situ treated/grafted chrome tanned collagen (hide powder) and pickled hide, respectively. The use of citric acrylate CAC oligomer instead of the traditional strong acids resulted in significant improvement in chrome exhaustion and physical properties of the leather.     

十八烷基-L-苯丙氨酸齐聚物在有机溶剂中的自组装

由L-苯丙氨酸和二(三氯甲基)碳酸酯反应得到的L-苯丙氨酸-N-羧基-环内酸酐(L-Phe-NCA), 在十八胺的引发下开环聚合得到十八烷基-L-苯丙氨酸齐聚物(简称L-Phe-R18). ¹H NMR (300 MHz)和FT-IR表征了产物结构, 是平均聚合度为5的齐聚物. L-Phe-R18能在多种有机溶剂中发生聚集和自组装, 并进而在这些有机溶剂中形成热可逆的物理凝胶. 其中, 该齐聚物能在氯苯、二苯醚、甲苯等溶剂中形成透明凝胶. 也能在苯、硝基苯、醋酸丁酯等溶剂中形成非透明凝胶. L-Phe-R18在这些有机溶剂中的最低凝胶化浓度(MGC)在w＝0.3%～1%之间. X射线衍射(XRD)数据和场发射扫描电镜(FE-SEM)以及分子模拟表征了L-Phe-R18聚集体的微观形态和可能的聚集方式. 认为L-Phe-R18在有机溶剂中通过分子间氢键、π-π堆积等非共价键相互作用聚集、组装成厚度约为20 nm左右的带状纤维, 溶剂分子以毛细力存在于相互缠绕的纤维网络结构中, 使体系形成稳定的凝胶.     

Lipase‐Catalyzed Transformation of Unnatural‐Type Poly(3‐hydroxybutanoate) into Reactive Cyclic Oligomer

Unnatural‐type syndiotactic and atactic poly[(R,S)‐3‐hydroxybutanoate]s [P(3HB)s] were enzymatically transformed into a reactive cyclic 3HB oligomer of molecular weight ca. 500 in an organic solvent, such as toluene, using immobilized lipase from Candida antarctica at 40°C for 24 h. It was confirmed that similar results were obtained for both syndiotactic and atactic P(3HB)s. On the other hand, the acidic degradation of these polymers using a protonic acid, such as p‐toluenesulfonic acid, exclusively produced the linear 3HB oligomer instead of the cyclic oligomer. The formation of the cyclic oligomer was regarded as the characteristic feature of the lipase‐catalyzed degradation in organic media. The cyclic oligomer obtained readily reacted with alcohol as a nucleophile, and using lipase, to produce the alkyl ester of the 3HB oligomer.     

Viscosity of dispersedly filled epoxy compositions

Viscosity η of ED-20 oligomer modified by different amounts C of aerosil, carbon black, and multiwall carbon nanotubes is measured by the rotational viscometry method in the temperature interval of 20–80°C. It is shown that the shape of η-C curves depends on the temperature, nature, and shape of particles. With filling by aerosil and carbon black, the η-C dependence is described by curves with minimums at 20°C. Possible mechanisms of the phenomena observed are considered.     

Preparation of amphiphilic networks by Diels-Alder reactions between oligo(butyl methacrylate) with furan end-groups and a poly(ethylene oxide-co-acetylenedicarboxylate)

A butyl methacrylate oligomer with furan end-groups was synthesized by ozonolysing a poly(butyl methacrylate-co-butadiene) latex. The end-groups of this oligomer were amidated with aminomethylfuran to give a coagulated mass of derivatized oligomers. This furan functional oligomer was then mixed with poly(ethylene oxide-co-acetylenedicarboxylate) and heated at 60°C or 125°C. The material cured at 125°C was found to contain a higher gel fraction (55 wt.-%) than that cured at 60°C (30 wt.-%).     

Electrospun electroactive nanofibers of gelatin‐oligoaniline/Poly (vinyl alcohol) templates for architecting of cardiac tissue with on‐demand drug release

In this study, grafted gelatin with oligoaniline (GelOA) was synthesized and then mixed with Poly (vinyl alcohol) (PVA). Several scaffolds with different ratio of PVA/GelOA were electrospun to fabricate electroactive scaffolds. GelOA was characterized using Fourier‐transform infrared spectroscopy (FTIR); moreover, nanofiber properties were evaluated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) analyses. Nanofibers diameter was decreased with aniline oligomer increment form 300 to 150 nm because of the hydrophobic nature of the aniline oligomer. Aniline oligomer electroactivity was studied using cyclic voltammetry, which exhibited two redox peaks at 0.4 and 0.6. Moreover, aniline oligomer enhancement resulted in melting point increasing from 220°C to 230°C because of the crystallinity increment. To assess the biocompatibility of nanofibers, cell viability and cell adhesion were tracked using mesenchymal stem cell (MSCs). It was revealed that the presence of aniline oligomer leads to enhancing the conductivity, thermal properties and lowering the degradation rate and drug release. Among of different scaffolds, sample with high content of GelOA shows better behavior in physical and biological properties. Accumulative drug releases under applied electrical field at 40 minutes showed that the drug release for stimulated condition is about 33% more than the unapplied electrical field one.     

Study of structuring of surface-modified technical-grade carbon particles with metal oxides in oligo(divinyl-isoprene)

Effect of a nanosize coating of technical-grade carbon particles with metal oxides NiO, CuO, PbO, and Bi₂O₃ on processes in which continuous carbon structures are formed in an oligomer formulation was studied. The elastic and dissipative constituents of rheological properties of the 3D carbon structures being formed were determined. An optical method and computerized data processing yielded data on structuring of a filled oligomer system under various testing conditions.     

气相色谱-质谱法研究低分子量高含氢聚硅氧烷的组成

低分子量高含氢聚硅氧烷应用广泛,但组成复杂。实验建立了高含氢聚硅氧烷组成的分析方法。采用气相色谱质谱联用仪,对高含氢聚硅氧烷进行了分析,通过谱图解析和谱峰的规律性研究,共确定了样品中38个组分,包含有4组同系物:3种链状高含氢聚硅氧烷和1种环状高含氢聚硅氧烷。采用气相色谱方法对各组分进行了定量分析,研究结果对于改进生产工艺和提高低分子量聚硅氧烷的性能具有理论指导意义。     

Polycarbonate synthesis by the melt phase carbonate-ester interchange reaction of bisphenol-A diacetate with dimethyl carbonate

The molecular weight of polycarbonate formed by the carbonate-ester interchange reaction of bisphenol-A diacetate (BPAC₂) and dimethyl carbonate (DMC) was found to depend on the composition of the oligomer formed in its first stage. At a [DMC] : [BPAC₂] ratio of 2, an oligomer with relatively higher acetate end group concentration was formed. This upon further polycondensation yielded a polycarbonate of inherent viscosity, 0.2-0.25 dL/g. Upon addition of DMC at a later stage in the oligomer-forming reaction, an oligomer containing relatively higher carbonate end groups could be obtained. These oligomers gave polycarbonates higher inherent viscosity, 0.4-0.5 dL/g. It is therefore proposed that oligomers having carbonate end groups are more reactive in self-polycondensation than those containing acetate end groups. © 1995 John Wiley & Sons, Inc.     

Determination of hexamethylene diisocyanate-based isocyanates in spray-painting operations. Part 2. Comparison of high performance liquid chromatography with capillary zone electrophoresis

A capillary zone electrophoresis (CZE) approach was developed for the determination of hexamethylene diisocyanate (HDI) monomer and HDI-based oligomers. A comparison of CZE with high performance liquid chromatography (HPLC) indicates that the CZE separation completely isolates isocyanates from excess solvent, derivatizing reagent and pigment while offering a fivefold increase in sensitivity. The CZE approach allows for the quantification of HDI monomer and oligomer within a 1 min time window under the run conditions selected. For the determination of HDI-based oligomer, provided that the relative response with respect to HDI monomer is calculated, there is no significant difference (p < 0.05, n = 10) in the isocyanate air concentration when using either HPLC or CZE. The results are significant because they indicate that CZE has advantages for the determination of both HDI-based oligomer and HDI monomer generated during spray-painting operations.     

Estimation of interaction energies by the critical molecular weight method: 1. Blends with polycarbonates

The interaction energies between PS, Pα-MS, and PMMA with several bisphenol-A-based polycarbonates were quantitatively determined from oligomer/oligomer, oligomer/homopolymer, and homopolymer/copolymer blends. Interaction energies were calculated from the Flory-Huggins theory and the Sanchez-Lacombe equation of state theory using experimental cloud points or miscibility boundaries. Alkyl addition to the phenyl rings of polycarbonate is favorable for miscibility with polystyrene whereas halogenation of the bisphenol connector unit is favorable for miscibility with poly(methyl methacrylate). Interaction energies are quantitatively ranked and described qualitatively in terms of changes in the electronic charge distribution of the polymer repeat units as calculated by SYBYL software. © 1994 John Wiley & Sons, Inc.     

Reaction of elemental phosphorus with epoxides

Conclusions The reactions of P₄/propylene oxide/Me₃N/HX (mole ratio=150.81) leads to the formation of an oligomer. The chain of this oligomer features the sequence of -C-P(O)-O-fragments. Features were determined which control the rate of P₄ conversion depending on the composition of the reaction mixture. The oligomer composition was determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1399–1402, June, 1987.     

Preparation of a new composite consisted of titanate nanotubes and porphyrin oligomer by a capillary filling

Titanate nanotubes (TNTs) with high aspect ratio were synthesized via a hydrothermal process. By means of a capillary filling method, the porphyrin oligomers dissolved in the tetrahydrofuran solution could be easily incorporated into the pore channels of TNTs. Transmission electron microscopy of the resulting one-dimensional TNTs/porphyrin oligomer composite showed that the pore channels of TNTs were blurred. The results of solid UV–vis diffuse reflectance spectra, fluorescence spectra and Fourier transform infrared spectra further confirmed that the porphyrin oligomers have successfully been incorporated into the pore channels of TNTs by the host–guest interaction between TNTs and the porphyrin oligomers. The investigation of thermal stability revealed that the porphyrin oligomers in the composite became more stable due to the shielding of TNTs.     

Influence of isocyanate type of acrylated urethane oligomer and of additives on weathering of UV-cured films

The weathering of UV-cured films containing the isocyanate type of acrylated urethane oligomer, and the influence of different additives (HALS, UVA and TiO₂), was investigated by various methods. The UV-cured film containing the acrylated aromatic urethane oligomer showed worse photodegradation than that containing the acrylated aliphatic urethane oligomer. In the case of the UV-cured films containing the acrylated aromatic urethane oligomer, those stabilized using both HALS and UVA showed the highest photostability.     

Quantitative studies of interaction between complementary polymers and oligomers in solutions

A theoretical model for interpolymer reaction of the type: matrix + oligomer ? polycomplex has been considered. Matrix and oligomer are complementary macromolecules with the matrix chain length substantially greater than that of the oligomer chain. Theoretical relations connecting the conversion degree in the interpolymer reaction with temperature, oligomer length and oligomer concentration are developed. The limits for application of the considered theoretical model are indicated. High selectivity of the interpolymer reaction with respect to the oligomer chain length is predicted theoretically. The validity of the theoretical relations is demonstrated by the reactions between polycarboxylic acids and polyethylene glycol in aqueous and water-methanol media. The selectivity of the interpolymer reactions with respect to chain length is experimentally proved for the example of fractionated relatively low molecular poly-N-vinyl pyrrolidone complexing with polyacrylic acid.     

High-pressure synthesis of cyclic phenylacetylene oligomer

New conjugated oligomers were prepared by reacting phenylacetylene under high pressure of 0.11 to 0.92 GPa at 100–200°C for 0–5 h. The number-average molecular weight M?_n, the weight-average molecular weight M?_w, and the oligomer yield increased with pressure, tem-perature, and time. The average molecular weight of the oligomer showed the maximum value (M?_n: 830, M?_w: 2400) under 0.92 GPa, the maximum pressure, where phenylacetylene was oligomerized at a constant temperature. The structure of the oligomer was investigated from ESR, infrared, UV–VIS, field desorption mass (FDMS) spectra, and ¹³C NMR spec-trum. Analysis of the FDMS spectrum revealed that the molecular weight of the oligomer was multiple of the monomer. ¹³C NMR spectrum of the oligomer showed the absence of sp-carbon (? C?). We found that the oligomer had a cyclic structure. The cyclic oligomers of pentamer or more were new compounds. © 1995 John Wiley & Sons, Inc.     

Estimation of interaction energies by the critical molecular weight method: 2. Blends with polysulfones

The interaction energies between PS, Pα-MS, and PMMA, as well as acrylonitrile and maleic anhydride units, with a series of polysulfones were quantitatively determined from oligomer/oligomer, oligomer/homopolymer, and homopolymer/copolymer blends. Interaction energies were calculated from the Flory-Huggins theory and the Sanchez-Lacombe equation of state theory using experimental cloud points or miscibility boundaries. Alkyl addition to the phenyl rings of polysulfone is favorable for miscibility with polystyrene whereas halogenation of the bisphenol connector unit favors miscibility with poly(methyl methacrylate). Interaction energies are quantitatively ranked and described qualitatively in terms of changes in the electronic charge distribution of the polymer repeat units as calculated by SYBYL software. © 1994 John Wiley & Sons, Inc.