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1.
Preparation of Cyclophosphates, Cyclophosphatophosphonates, Diphosphonates, and Di-phosphites in Urea Melts Ammonium cyclotriphosphate (NH4)P3O9, ammonium cyclotetraphosphate [PIV? PIV ? O? ]2, ammonium cyclotriphosphatophosphonates Ammonium organyldiphosphonates And ammonium diphosphites are prepared in high yields on heating acidic phosphates, phosphonates, and phosphites in urea or urea/ammonium nitrate melts. The mechanism of the dehydration of phosphorus compounds containing POH groups in molten urea is discussed.  相似文献   

2.
Summary: A scalable synthesis of copper nanowires by alternating current electrodeposition into porous aluminium oxide was used to produce multigram quantities of 16 nm diameter by >2 µm long nanowires. Polystyrene nanocomposites were prepared by solution processing. The composites containing unpassivated nanowires were non‐uniformly dispersed and showed electrical percolation at ≈2 vol.‐% Cu loading, while the composites containing HSC18H37‐passivated nanowires were uniformly dispersed, but remained resistive up to at least 10 vol.‐% Cu loading.

Copper nanowires prepared by alternating current electrodeposition into porous aluminium oxide templates.  相似文献   


3.
The Fatigue Crack Propagation (FCP) behavior of block amide copolymers is investigated as a function of molecular weight, rubber toughening as well as environmental conditions. The enhancement of FCP resistance with increasing average molecular weight is shown and correlated to features observed on the fracture surface. Particular attention is paid to hysteretic heating, measured with an infrared camera, in the crack tip zone of different average molecular weight copolymers and rubber-toughened copolymer. A FCP approach of stress-cracking in an aqueous solution of zinc chloride is proposed here. An improvement in FCP resistance as the average molecular weight increases, similar to that exhibited in normal environment, appears. The shift in da/dN values over the tested range of can be approximated by an exponential function:   相似文献   

4.
Summary: We describe an interesting approach to the fabrication of wettability gradients from hydrophobicity to superhydrophobicity in low‐density polyethylene (LDPE) films by first forming high porosity surfaces and placing the specimens onto linear temperature gradients. While the polymer chosen for the study is non‐polar, its microporous layer provides sufficient superhydrophobicity. Lateral gradient heating of the layer results in partial melting of the polymer and correspondingly decreases porosity thus decreasing hydrophobicity.

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5.
The synthesis of polythioethers of the form was effected, where Cp denotes cyclopentadienyl. Four reaction systems were studied and evaluated. Two proved to be undesirable (the “reverse” interfacial and organic solution methods), while two proved acceptable (the “normal” interfacial and aqueous solution methods). A number of added bases were evaluated. Et3N and NaOH were found to be acceptable. Yield increases with reaction time for aqueous solution syntheses, while yield remains constant with reaction time for synthesis via the normal interfacial method.  相似文献   

6.
A reactivity study of the most important elementary steps (propagation, intermolecular degradative transfer, and re‐initiation) in free‐radical polymerization of acrylfuranic systems, furfuryl acrylate (FA), and furfuryl methacrylate (FM), using the frontier molecular orbital theory is described. A qualitative explanation of reactivity trends of these steps for both systems is given based on absolute values of the SOMO/HOMO gap. The small difference between values of kp for FA and FM compared to that found for MA and MMA ( ) is justified semi‐quantitatively by applying a formulation for the change of energy in the transition state using second‐order perturbation theory.

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7.
The formation of oxazolidines from propionaldehyde and aliphatic β-aminoalcohols is complicated by the appearance of appreciable amounts of unsaturated Schiff bases. The simple Schiff base, often the dominant species when aromatic aldehydes react with amines, could not be detected in the present aliphatic systems. We conclude that in aliphatic systems the order of stability is and . The gem-dimethyl group α to nitrogen stablizes the heterocyclic ring remarkably.  相似文献   

8.
Summary: The success of metathesis chemistry techniques has sparked a tremendous interest in polymer and material chemistry. This contribution provides an overview of the state of the art in ring opening metathesis polymerisation (ROMP). It is intended to provide the reader with useful information on the interplay of initiators, monomers, and reaction conditions, thus aiding polymer chemists to utilise the ROMP toolbox. Prominent and illustrative examples from current research are given in the article.

The “ROMP toolbox”.  相似文献   


9.
Transparent film materials with excellent mechanical and thermal properties were elaborated by drying a latex suspension of armored polymer/Laponite composite particles. Low‐temperature TEM observation of ultrathin cross‐sections of the films indicated a unique network morphology characterized by a “honeycomb” distribution of the Laponite platelets remindful of the original particles morphology.

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10.
Titanium polyesters of the form where Cp denotes cyclopentadiene, have been synthesized by utilizing both the interfacial and solution techniques. Polymer yield increases with reaction time. The reactive titanium reactant in the solution polycondensations is believed to be the Cp2Ti+2 cation.  相似文献   

11.
The reactions where Y = CH3 (M), C2H5 (E), i? C3H7 (I), and t? C4H9 (T) have been studied between 488 and 606 K. The pressures of CHD ranged from 16 to 124 torr and those of YE from 57 to 625 torr. These reactions are homogeneous and first order with respect to each reagent. The rate constants (in L/mol·s) are given by The Arrhenius parameters are used as a test for a biradical mechanism and to discuss the endo selectivity of the reactions.  相似文献   

12.
POSS‐functionalized polyisobutylenes (PIBs) were synthesized by carbocationic polymerization using an epoxy‐POSS/TiCl4 initiating system in hexane/methyl chloride (60:40 v/v) solvent mixture at −80 °C. 1H NMR spectroscopy verified the incorporation of one epoxy‐POSS per polymer chain. Light scattering and TEM analysis demonstrated the formation of 50–100 nm sized aggregates and micron‐sized clusters.

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13.
Dinucleation of TiCl4 on the MgCl2 (100) surface has been conventionally believed as the origin of the stereospecificity of heterogeneous Ziegler‐Natta catalysts for propylene polymerization, while the MgCl2 (110) surface has been regarded as non‐stereoselective in the absence of organic donors. Based on periodic density functional calculations, we propose a new isospecific Ti dinuclear species on the MgCl2 (110) surface, which is formed as a result of reduction of Ti from 4+ to 3+. The new species closely resembles the dinuclear species on the (100) surface, but two Ti ions are obliquely stacked along the (110) surface through Cl bridges. The results address the importance of the reduction and re‐distribution of surface Ti species after contacting with cocatalysts in considering the origin of the stereospecificity.

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14.
Specific losses of water are observed from the molecular anions of monoximes of α-diketones. Labelling studies, kinetic energy release values and the +E spectra of ions have been used to aid in the elucidation of the fragmentation pathways. It is proposed that the majority of ions have α-keto nitrile structures.  相似文献   

15.
Aqueous sols of TiO2 (anatase, particle radius 25 Å) were excited with (347.1 nm)-laser light and the reaction of valence-band holes with halide ions (X = I?, Br?, Cl?) was investigated. Hole transfer takes place within the duration of the (10 ns)-laser pulse and results in the formation of anion radicals according to the sequence: The quantum yield of X increases in the order Cl < Br < I, attaining 0.8 for I at pH 1. It is affected by pH, halide concentration and the presence of a protective agent for the sol. RuO2 deposited onto TiO2 enhances markedly Cl and Br -formation, but has no effect on the yield of I. Laser-photolysis investigation of halide oxidation were also carried out with colloidal Fe2O3 (particle radius 600 Å). For I2?formation, the quantum yield exceeds 0.9 indicating almost quantitative hole scavenging by iodide.  相似文献   

16.
Poly(2‐alkyl‐2‐oxazoline)s can be regarded as pseudo‐peptides or bioinspired polymers, which are available through living/controlled cationic polymerization and polymer (“click”) modification procedures. Materials and solution properties may be adjusted via the nature of the side chain (hydrophilic‐hydrophobic, chiral, bio‐functional, etc.), opening the way to stimulus‐responsive materials and complex colloidal structures in aqueous environments. Herein, we give an overview over the macromolecular engineering of polyoxazolines, including the synthesis of biohybrids, and the “smart”/bioinspired aggregation behavior in solution.

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17.
Conformational analysis of macromolecular structures reveals interesting higher‐order spatial arrangements. Analyzing these features as a function of time provides insights into the dynamical behavior of these systems and the identification of relevant subdomains. We present some visual‐analytic methods that we devised to explore the spatial‐temporal properties from molecular dynamics simulation data. These methods automatically detect common features and connect them to properties of interest. These methods yield physical insights that are not easily obtainable with existing methods for particle simulation data, as illustrated for polyacetylene interacting with a carbon nanotube.

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18.
IR-spectroscopic investigations of light-induced rearrangement reactions of nitrosooxymethane (CH3ONO3), nitrosooxyethane (CH3CH2ONO) and N,N-dimethylnitrosamine ((CH3)2NNO) in low-temperature rare-gas matrices have established that these molecules are transformed in two photolysis steps to the previously unknown C-nitroso compounds nitrosomethanol (CH2(OH)(NO)), 1-nitrosoethanol (CH3CH(OH)(NO)), and methyl(nitrosomethyl)amine CH2(NO)(NH)(CH3). Evidence for a similar rearrangement reaction has been advanced for N-Nitrosopyrrolidine which is converted to C-nitrosopyrrolidine . The matrix-isolation technique in combination with wavelength-selective irradiation allowed to trap and characterize an intermediate of rearrangement which revealed to be nitroxyl (HNO) complex (CH2…HNO, CH3CHO…HNO, CH3N = CH2…HNO, and ). Since these findings have a close resemblance with rearrangement reactions of more complex nitrosooxy compounds, nitrosamines, or nitrosohydrazines used in organic synthesis, it is suggested that also in these reactions nitroxyl is present as an intermediate species.  相似文献   

19.
Summary: The evolution of the photoinduced birefringence in thin films of narrow polymer fractions is studied and compared with the behavior of the non‐fractionated polymer. The Δnind value decreases by increasing the degree of polymerization ( ) within the oligomeric range but becomes independent of molecular weight starting from a of ≈70. Thermal pretreatment of the films results in higher photoinduced birefringence. The films show good stability of the photorecording.

Birefringence induced after 10 min, Δnind(600) and its growth rate at the same moment versus molecular weight.  相似文献   


20.
The structure of the tetrameric dianion formed by α-methylstyrene in tetrahydrofuran by reaction with sodium has been examined. Mass spectral, NMR, infrared, and kinetic data all indicate that the structure is rather than the structure which had previously been assumed for this species.  相似文献   

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