KF-蒙脱土催化下丙二腈与α,β-不饱和酮的迈克尔加成反应

本论文研究了KF-蒙脱土催化下丙二腈与α,β-不饱和酮的迈克尔加成反应,研究发现在不同的反应温度下可以得到加成和环化两种不同的产物。该方法和现有的方法相比具有产率高、反应条件温和、操作简单、试剂易得等优点。     

Fabrication of a Covalently Attached Multilayer Film via In‐Situ Reaction

A covalently linked ultrathin multilayer film was fabricated from 2‐nitro‐N‐methyl‐diphenylamine‐4‐diazonium‐formaldehyde resin (NDR) and phenol‐formaldehyde resin (PR) in methanol in‐situ. The UV‐vis, XRD, AFM and FTIR show that this multilayer is of high regularity, smoothness and stability.     

Single‐Handed Helical Carbonaceous Nanotubes: Preparation,Optical Activity,and Applications

Carbon‐based nanomaterials have been widely studied in the past decade. Three approaches have been developed for the preparation of single‐handed helical carbonaceous nanotubes. The first approach uses the carbonization of organopolymeric nanotubes, where the organic polymers are polypyrrole, 3‐aminophenol‐formaldehyde resin, and m‐diaminobenzene‐formaldehyde resin. The second approach uses the carbonization of aromatic ring‐bridged polybissilsesquioxane followed by the removal of silica. Micropores exist within the walls of the carbonaceous nanotubes. The third approach uses the carbonization of organic compounds within silica nanotubes. This hard‐templating approach drives the formation of helical carbonaceous nanotubes containing twisted carbonaceous nanoribbons. All of these helical carbonaceous nanotubes exhibit optical activity, which is believed to originate from the chiral π‐π stacking of aromatic rings. They can be used as chirality inducers, and for lithium‐ion storage.     

Comparative use of solvent‐free KF‐A12O3 and K2CO3 in acetone in the synthesis of quinoxaline 1,4‐dioxide derivatives designed as antimalarial drug candidates

In this paper we describe two new basic conditions for the synthesis of quinoxaline 1,4‐dioxide derivatives in moderate to good yields. These conditions, exemplified by the use of K₂C0₃ in acetone or KF/A1₂0₃ in the absence of an organic solvent, were reproducible and applicable to the synthesis of 2‐(carboethoxy)‐3‐phenylquinoxaline 1,4‐dioxide derivatives substituted in position 4 with electron‐donating or electron‐withdrawing groups.     

Determination of 3‐chloro‐1,2‐propanediol in polyamideamine epichlorohydrin resin solution by reaction‐based headspace gas chromatography

We report on a headspace gas chromatographic method for determining the content of 3‐chloro‐1,2‐propanediol in polyamideamine epichlorohydrin resin solution. It was based on quantitatively converting 3‐chloro‐1,2‐propanediol to formaldehyde by periodate oxidation in a closed headspace sample vial at a room temperature for 10 min, and then to methanol by borohydride reduction at 90°C for 40 min followed by the headspace gas chromatographic measurement. The results showed that the present method has an excellent measurement precision (relative standard deviation < 2.60%) and accuracy (recoveries from 96.4–102%) in 3‐chloro‐1,2‐propanediol analysis. The limit of quantitation was 0.031 mg/mL. It is simple and suitable for determining the 3‐chloro‐1,2‐propanediol content in polyamideamine epichlorohydrin resin solution.     

Doped Nano‐Sized Copper(I) Oxide (Cu2O) on Melamine?Formaldehyde Resin: a Highly Efficient Heterogeneous Nano Catalyst for ‘Click’ Synthesis of Some Novel 1H‐1,2,3‐Triazole Derivatives Having Antibacterial Activity

A facile and simple protocol for the 1,3‐dipolar cycloaddition of organic azides with terminal alkynes catalyzed by doped nano‐sized Cu₂O on melamine? formaldehyde resin (nano‐Cu₂O? MFR) as a new and convenient heterogeneous catalyst is described. In this method, ‘click’ cycloaddition of various structurally diverse β‐azido alcohols and alkynes in the presence of nano‐Cu₂O? MFR in H₂O/THF 1 : 2 furnished the corresponding 1,4‐disubstituted 1H‐1,2,3‐triazole adducts 1a – 1o in good to excellent yields at room temperature (Scheme and Table 3). The nano‐Cu₂O? MFR was characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), inductively coupled plasma (ICP) analysis, and FT‐IR. The nano‐Cu₂O? MFR could be easily recovered and recycled from the reaction mixture and reused for many consecutive trials without significant decrease in activity (Table 4). The in vitro antibacterial activities of all synthesized compounds were tested on several Gram‐positive and/or Gram‐negative bacteria (Table 5). The results demonstrate the promising antibacterial activity for some of the synthesized compounds.     

Synthesis of Nanocomposites from Pd0 and a Hyper‐Cross‐Linked Functional Resin Obtained from a Conventional Gel‐Type Precursor

Hyper‐cross‐linked resins stemming from a gel‐type poly‐chloromethylated poly(styrene‐co‐divinylbenzene) resin (GT) have been investigated by a multi‐methodological approach based on elemental analysis, scanning electron microscopy, X‐ray microanalysis, and solvent absorption. The hyper‐cross‐linking of the parent resin was accomplished by Friedel–Crafts alkylation of the phenyl rings of the resins with the chloromethyl groups. This produced a permanent pore system comprising both micropores (<2.0 nm in diameter) and mesopores (2.2 nm). The chloromethyl groups that did not react in the hyper‐cross‐linking step were transformed into methylmercaptan groups and the latter were then converted into sulfonic groups by oxidation with hydrogen peroxide. By this procedure the extensive permanent porosity of the parent unsulfonated hyper‐cross‐linked polymer (HGT) was retained by the sulfonated polymer (HGTS). The final exchange capacity of HGTS was determined to be 0.36 mmol g^?1. HGTS was easily metalated with Pd^II and the subsequent reduction of the metal centers with either aqueous sodium borohydride, formaldehyde, or dihydrogen produced three Pd⁰/HGTS nanocomposites. The metal nanoparticles had diameters in the 1–6 nm range for all the nanocomposites, as determined by TEM, but with somewhat different distributions. When formaldehyde was used, more than 90 % of the nanoparticles were less than 3 nm and their radial distribution throughout the polymer beads was quite homogeneous. These findings show that with this reducing agent the metal nanoparticles are generated within the pore system of the polymer matrix, hence their size is controlled by the dimensions of the pores of the polymeric support.     

Polyoxometalate and Resin‐Derived P‐Doped Mo2C@N‐Doped Carbon as a Highly Efficient Hydrogen‐Evolution Reaction Catalyst at All pH Values

A new type of P‐doped Mo₂C coated by N‐doped carbon (P‐Mo₂C@NC) has been successfully prepared by calcining a mixture of H₃[PMo₁₂O₄₀] polyoxometalates (POMs) and urea‐formaldehyde resin under an N₂ atmosphere. Urea‐formaldehyde resin not only serves as the carbon source to ensure carbonization but also facilitates the uniform distribution of POM precursors, which efficiently avoid the aggregation of Mo₂C particles at high temperatures. TEM analysis revealed that the average diameter of the Mo₂C particles was about 10 nm, which is coated by a few‐layer N‐doped carbon sheet. The as‐prepared P‐Mo₂C@NC displayed excellent hydrogen‐evolution reaction (HER) performance and long‐term stability in all pH environments. To reach a current density of 10 mA cm^?2, only 109, 159, and 83 mV were needed for P‐Mo₂C@NC in 0.5 m H₂SO₄ (pH 0), 0.1 m phosphate buffer (pH 7), and 1 m KOH (pH 14), respectively. This could provide a high‐yield and low‐cost method to prepare uniform nanosized molybdenum carbides with highly efficient and stable HER performance.     

Fire‐Retardant and Thermally Insulating Phenolic‐Silica Aerogels

Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co‐polymerization and nanoscale phase separation of the phenol‐formaldehyde‐resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO₂ aerogel can resist a high‐temperature flame without disintegration and prevents the temperature on the non‐exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures.     

Structural characteristics of p‐t‐Octylphenol formaldehyde resole resins using molecular simulation

p‐t‐Octylphenol formaldehyde resole resins have two linkage types of methylene‐ and dimethylene ether‐linkages and have three terminal types of hydrogen, methylol, and o‐methylene quinone. Variation of structural characteristics of the resins due to different types of linkages and terminals were studied using molecular dynamics and molecular mechanics. The structural characteristics of the methylene‐bridged resins were intramolecular hydrogen bonds between hydroxyl groups of the adjacent p‐t‐octylphenols. In the dimethylene ether‐bridged resin, the intramolecular hydrogen bonds between oxygen atoms of the dimethylene ether‐linkages and hydroxyl groups of the neighboring phenolic units were found. For the resins with both methylol terminals, one of both terminals of the resins was hidden at the center of the molecule when the resin size is large. The number of hydrogen bonds in the resins with the methylol terminal was larger than for the resins with the o‐methylene quinone terminal. Variation of the structural characteristics of the resins by dehydration of the terminal methylol was discussed. Using the calculated results, dissociation of the dimethylene ether linkage and crosslinking reaction of rubber chains by the resin were explained. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of ether‐linked bisoxazolines and their use in step‐growth polymerization reactions with phenolics

Six new ether‐linked bisoxazolines have been synthesized via reaction of p‐hydroxyphenyl‐2‐oxazoline with dihalides. These bisoxazolines may be used as chain extenders or crosslinkers for resins, monomers or polymers containing various acidic groups, including phenolics, via step‐growth (1 : 1) reactions. As an illustration, a phenol‐formaldehyde polycondensate (Alnovol) and an enzyme oligomerized bisphenol A resin, as well as poly (p‐hydroxystyrene), was chain extended and crosslinked to produce thermosets with high glass transition temperatures. The new bisoxazolines were also polymerized with diphenol compounds, such as diphone D and bisphenol P to generate linear or branched oligomers and polymers. Differential scanning calorimetry was used to evaluate the potential for polymerization and crosslinking reactions. Preliminary results showed that the new, ether‐linked bisoxazolines have potential for formulating high performance thermosets. Copyright © 2002 John Wiley & Sons, Ltd.     

Ultrafast Preparation of AIE‐Active Fluorescent Organic Nanoparticles via a “One‐Pot” Microwave‐Assisted Kabachnik–Fields Reaction

The development of effective strategies for fabrication of fluorescent organic nanoparticles (FONs) with an aggregation‐induced emission (AIE) feature has an important impact on the biomedical applications of these AIE‐active FONs. In the current work, an ultrafast strategy for fabricating AIE‐active FONs is developed through a “one‐pot” microwave‐assisted, catalysts‐free, and solvent‐free Kabachnik–Fields (KF) reaction for the first time. It is demonstrated that such organophosphorous‐containing AIE‐active block polymers can be synthesized within 2 min under air atmosphere through the microwave‐assisted KF reaction. These polymers show amphiphilic properties and can self‐assemble into mPEG‐CHO‐Phe‐NH₂‐DEP FONs, which display high water dispersibility and desirable optical properties. Biological evaluation results suggest that the mPEG‐CHO‐Phe‐NH₂‐DEP FONs exhibit low toxicity and are potential for biological imaging applications. More importantly, many other multifunctional AIE‐active FONs can also be fabricated through the strategy described in this work owing to the universality of KF reaction. Besides, combined with the excellent properties of mPEG‐CHO‐Phe‐NH₂‐DEP FONs, it is believed that such microwave‐assisted KF reaction shall be an effective route for designing various AIE‐active nanomaterials for different biomedical applications.

     

The Reaction Mechanism of the Transetherification and Crosslinking of Melamine Resins

Melamine formaldehyde resins (MFR) are well known resins in the wood board and paper coating market. Etherified MFR's are applied as crosslinkers in the automotive coating industry. In Europe the growth of the market and the research activities are relatively small. On the other side in comparison to other polymers outstanding properties are possible to realize. So the development of new melamine ether resins (MER) was started. MER is a partly methylolated and fully etherified resin with a highly stable “thermoplastic” processing range. The MER's themselves are transparent granulates with enough stability for storage and transport. The crosslinking reaction can be started either by thermal or acidic catalytic activation, without losses of formaldehyde. Transetherifications with oligomeric diols can lead to more elastic and higher molecular melamine polyether resin (MPER) structures. The reaction mechanism and the crosslinking kinetics of the partly methylolated melamine ethers of methanol in comparison to the fully methylolated hexamethylol melamine ether will be discussed in this paper.     

Effect of the organophosphate structure on the physical and flame‐retardant properties of an epoxy resin

2‐(6‐Oxido‐6H‐dibenzo〈c,e〉〈1,2〉oxa‐phosphorin‐6‐yl)1,4‐benzenediol (ODOPB) and bis(3‐dihydroxyphenyl) phenyl phosphate (BHPP) were successfully synthesized and used as reactive flame retardants in o‐cresol formaldehyde novolac epoxy resin. Because of the rigid, cyclic, side‐chain structure of ODOPB, the resultant phosphorus‐containing epoxy resin exhibited a higher glass‐transition temperature, better flame retardancy, higher modulus, and greater thermal stability than the regular bromine‐containing tetrabromobisphenol A epoxy resin and the linear, main‐chain, phosphorus‐containing BHPP epoxy resin. A UL‐94VO rating was achieved with a phosphorus content as low as 1.1% with ODOPB (comparable to a bromine content of 12% and a phosphorus content of 2.2% with BHPP) in the cured resins, and no fumes or toxic gas emissions were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 369–378, 2002     

Self‐Sufficient Formaldehyde‐to‐Methanol Conversion by Organometallic Formaldehyde Dismutase Mimic

The catalytic networks of methylotrophic organisms, featuring redox enzymes for the activation of one‐carbon moieties, can serve as great inspiration in the development of novel homogeneously catalyzed pathways for the interconversion of C₁ molecules at ambient conditions. An imidazolium‐tagged arene–ruthenium complex was identified as an effective functional mimic of the bacterial formaldehyde dismutase, which provides a new and highly selective route for the conversion of formaldehyde to methanol in absence of any external reducing agents. Moreover, secondary amines are reductively methylated by the organometallic dismutase mimic in a redox self‐sufficient manner with formaldehyde acting both as carbon source and reducing agent.     

Azide/alkyne‐“click”‐reactions on amino resin materials: An LC‐ESI‐TOF analysis

This article describes the reaction of amino resins with functional molecules using the azide/alkyne‐“click”‐reaction, opening a simple chemical modification of amino resins under aqueous conditions. Alkyne‐modified melamine‐formaldehyde resins are prepared via a direct cocondensation approach using propargylic alcohol (21.6–86.3 mmol) as additive. Subsequently, alkyne‐modified mono‐, bi‐, and trinuclear melamine‐species are identified via LC‐ESI‐TOF methods proving the covalent incorporation of alkyne‐moieties in amounts of up to 3.9 mol %. Subsequent modification of the alkyne‐modified resins was accomplished by reaction of functional azides (octyl azide (1), (azidomethyl)benzene (2), 1‐(6‐azidohexyl) thymine (3), and 4‐azido‐N‐(2,2,6,6‐tetramethylpiperidin‐4‐yl)benzamide (4)) with Cu(I)Br and DIPEA as a base. The formation of triazolyl‐modified MF‐resins was proven by LC‐ESI‐TOF methods, indicating the successful covalent modification of the amino resin with the azides 1 – 4 . © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Analysis of dammar resin with MALDI‐FT‐ICR‐MS and APCI‐FT‐ICR‐MS

Comprehensive analysis of high‐resolution mass spectra of aged natural dammar resin obtained with Fourier transform ion cyclotron resonance mass spectrometer (FT‐ICR‐MS) using matrix‐assisted laser desorption/ionization (MALDI) and atmospheric pressure chemical ionization (APCI) is presented. Dammar resin is one of the most important components of painting varnishes. Dammar resin is a terpenoid resin (dominated by triterpenoids) with intrinsically very complex composition. This complexity further increases with aging. Ten different solvents and two‐component solvent mixtures were tested for sample preparation. The most suitable solvent mixtures for the MALDI‐FT‐ICR‐MS analysis were dichloromethane‐acetone and dichloromethane‐ethanol. The obtained MALDI‐FTMS mass spectrum contains nine clusters of peaks in the m/z range of 420–2200, and the obtained APCI‐FTMS mass spectrum contains three clusters of peaks in the m/z range of 380–910. The peaks in the clusters correspond to the oxygenated derivatives of terpenoids differing by the number of C₁₅H₂₄ units. The clusters, in turn, are composed of subclusters differing by the number of oxygen atoms in the molecules. Thorough analysis and identification of the components (or groups of components) by their accurate m/z ratios was carried out, and molecular formulas (elemental compositions) of all major peaks in the MALDI‐FTMS and APCI‐FTMS spectra were identified (and groups of possible isomeric compounds were proposed). In the MALDI‐FTMS and APCI‐FTMS mass spectrum, besides the oxidized C₃₀, triterpenoids also peaks corresponding to C₂₉ and C₃₁ derivatives of triterpenoids (demethylated and methylated, correspondingly) were detected. MALDI and APCI are complementary ionization sources for the analysis of natural dammar resin. In the MALDI source, preferably polar (extensively oxidized) components of the resin are ionized (mostly as Na⁺ adducts), whereas in the APCI source, preferably nonpolar (hydrocarbon and slightly oxidized) compounds are ionized (by protonation). Either of the two ionization methods, when used alone, gives an incomplete picture of the dammar resin composition. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of microencapsulated ammonium polyphosphate with montmorillonite‐melamine formaldehyde resin and its flame retardancy in EVM

Microencapsulated ammonium polyphosphate (MMT‐MF‐APP) with a montmorillonite‐melamine formaldehyde resin coating layer was successfully prepared by in situ polymerization. The product was characterized by Fourier‐transform infrared, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Water absorption analysis showed that the microencapsulation of APP with the MMT‐MF resin leads to a decrease in the particle's water solubility. The microcapsules also exhibited better mechanical properties and higher flame retardancy in the ethylene–vinyl acetate copolymer with high vinyl acetate content (EVM) rubber compared with the common ammonium polyphosphate. Moreover, thermogravimetric analysis results showed that the EVM composites with MMT‐MF‐APP and dipentaerythritol (DPER) as flame retardants possess higher thermal stability than those with common APP and DPER as flame retardants. Copyright © 2011 John Wiley & Sons, Ltd.     

Examination of selected synthesis parameters for typical wood adhesive‐type urea–formaldehyde resins by 13C NMR spectroscopy. I

Selected synthesis parameters of typical wood adhesive‐type urea–formaldehyde (UF) resins were examined using the ¹³C NMR spectroscopy. The monomeric hydroxymethylureas and methylene–ether derivatives formed in the initial alkaline reaction polymerize in the subsequent acidic reaction by forming methylene bonds and cleaving some hydroxymethyl groups as formaldehyde. For typical resin syntheses at F/U ratio of 2.10, the resulting UF polymer is found to be a number‐averaged pentamer having 3.25 polymer chain branches with about 80% of chain ends bonded to hydroxymethyl groups and the rest being free amide groups. When the second urea is added during the cooling period, about 67% of hydroxymethyl groups cleave from the UF polymeric components and the freed formaldehyde reacts with second urea to form monomeric hydroxymethylureas. This hydroxymethyl group move is suppressed when the second urea is added at low temperatures, suggesting that wood adhesive‐type UF resins are composed of monomeric and polymeric UF components having hydroxymethyl functional groups in varying proportions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 995–1007, 1999     

Synthesis and characterization of novel phenolic resins containing aryl‐boron backbone and their utilization in polymeric composites with improved thermal and mechanical properties

In the present study, a novel aryl‐boron‐containing phenolic resin named as PBPR has been synthesized from phenol and formaldehyde in the presence of phenylboronic acid. The chemical structure of the PBPR was confirmed by Fourier transform infrared, nuclear magnetic resonance and X‐ray photoelectron spectroscopy. The molecular weight, viscosity and curing behavior were examined to demonstrate that PBPRs have better processability than common boric acid‐modified phenolic resin. The thermal stability and fracture toughness of the cured PBPRs were greatly enhanced, where the char yield at 1000°C (nitrogen atmosphere) and the glass transition temperature reached 70.0% and 218°C, respectively. The excellent mechanical and ablative properties of the PBPR composites may have benefited from the good interfacial adhesion between the resin matrix and the reinforced fiber. The flexural strength and the linear ablative rate are 436.8 ± 5.2 MPa and 0.010 mm/sec, respectively. This study opens a new window for the preparation of high‐performance ablative composites by designing a resin matrix containing an aryl‐boron backbone. Copyright © 2013 John Wiley & Sons, Ltd.