Improved facile synthesis of α-amino phosphonates by the reaction of α-amido sulfones with dialkyl trimethyl silyl phosphites catalyzed by Fe(III) chloride

An improved efficient synthesis of α-amino phosphonates has been discovered by the reaction of N-benzyloxycarbonylamino sulfones with dialkyl trimethyl silyl phosphites in the presence of FeCl₃ as a catalyst. The products were formed in high yields (86–94%) within 2–4?h. The catalyst is inexpensive, easily available, and highly active. The unreacted dialkyl trimetyl silyl phosphites can easily be removed from the products due to their low boiling points. The sulfones can conveniently be prepared and are generally stable.     

Polyimides containing nonaromatic nitrogen linkages

Two diamines, 2,5-bis (4-aminophenyl)-2,5-diazahexane and 1,4-bis (4-aminophenyl)-1,4-diazacyclohexane were chosen as components for polyimidizations because they have melting points that differ by nearly 200°C (66–67 and 229–230°C, respectively) and are relatives of p-nitro-N,N-dimethylaniline. The melting points of the model compounds (phthalic anhydride) do not differ by as much as those of the free amines [303–304 and 386°C (DSC), respectively]. Six polyimides were prepared by a two-step polycondensation of the diamines with pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl) ethylidene] bis-1,3-isobenzofurandione. DSC thermograms failed to indicate any distinct transitions up to 450°C, however, the polyimide prepared from 2,5-bis (4-aminophenyl)-2,5-diazahexane and pyromellitic dianhydride shows a slight break in its DSC curve at 233°C.     

稳定分散的纳米银溶胶的制备及其表征

Stable aqueous dispersive colloidal Ag nanoparticles were prepared by reducing silver nitrate with sodium borohydride in the presence of 3-mercaptopropionic acid. The formation process of the Ag nanoparticles was investigated by UV-Visible spectroscopy and transmission electron microscopy. The results show that the spherical and rodlike particles and aggregates are formed in the initial stage of the reaction， then the rodlike particles and aggregates are gradually decomposed into small spherical particles， and the final obtained Ag nanoparticles with an average size of 8 nm are in uniform shapes and narrow size distribution， and the colloid remains stable for more than one month， which makes it convenient for use in practice. The presence of capping agent plays an extra role over nanoparticles stabilization and morphology. The presence of capping agent on the surface of Ag nanoparticle is confirmed by the X-ray photoelectron spectroscopy. It is found that Ag nanoparticles are negatively charged in alkaline condition， whereas they are positively charged in acid condition. Electrosteric effect is responsible for their long-term stability.     

Synthesis of aromatic poly(amide-imide)s from novel diimide-diacid (DIDA) containing sulphone and bulky pendant groups by direct polycondensation with various diamines

A novel diimide-diacid (DIDA) monomer, 4-{4-[(4-methyl phenyl) sulphonyl]}-1,3-bis-trimellitoimido benzene containing sulphone and bulky pendant groups was successfully synthesized and used to synthesize a series of wholly aromatic poly(amide-imide)s (PAIs) by direct polycondensation method. The direct polycondensation of newly synthesized DIDA with different diamines was carried out via Yamazaki’s phosphorylation method using triphenyl phosphite and pyridine system. The resulting poly(amide-imide)s were obtained in quantitative yields with inherent viscosities 0.36-0.47 dl/g in DMAc at 30 ± 0.1 °C. The poly(amide-imide)s were amorphous and were readily soluble in various solvents such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), and pyridine. Tough and flexible films were obtained by casting their DMAc solution. According to thermogravimetric analysis, the polymers were fairly stable up to temperature around 396 °C, and 10% weight losses in the temperature range of 476-511 °C that showed good thermal stabilities of these polymers.     

Paternò-Büchi反应的区域选择性

Paternò-Büchi(P-B)反应,即羰基-烯的[2+2]光环化加成反应,利用其特殊的区域及立体选择性可以合成一些结构精巧的取代氧杂环丁烷。随着P-B反应在有机合成中越来越广泛的应用,人们对P-B反应的区域选择性的研究也越来越深入。在P-B反应发现之初,人们一直用“最稳定的双自由基规则”解释其区域选择性,这一规则对有些体系却不适用,近年来有人开始运用“自旋化学”理论来解释区域选择性。本论文结合作者的研究工作,评述了近年来P-B反应的区域选择性的研究进展,重点阐述了反应温度、反应物的取代基对P-B反应区域选择性的影响及其规律。     

Fully Crosslinked Poly[cyclotriphosphazene‐co‐(4,4′‐sulfonyldiphenol)] Microspheres via Precipitation Polymerization and Their Superior Thermal Properties

Fully crosslinked, stable poly[cyclotriphosphazene‐co‐(4,4′‐sulfonyldiphenol)] (PZS) microspheres have been prepared via the polycondensation between hexachlorocyclotriphosphazene and 4,4′‐sulfonyldiphenol by precipitation polymerization. The diameter of the PZS microspheres ranged from 0.6 to 1.0 µm with the specific surface area of the microspheres ranging from 11.7 to 10.1 m² · g^?1. The formation of the non‐porous microspheres was observed to obey an oligomeric species absorbing mechanism. The fully crosslinked chemical structure of the PZS microspheres were determined by IR, CP/MAS NMR, XRD, and EDX. No glass‐transition temperature was observed and the onset of the thermal‐degradation temperature was 542 °C. Thermal stability of the PZS microspheres by the precipitation polycondensation was significantly improved as compared with crosslinked microspheres produced by addition polymerizations.

     

Lithium Germanate (Li2GeO3): A High‐Performance Anode Material for Lithium‐Ion Batteries

A simple, cost‐effective, and easily scalable molten salt method for the preparation of Li₂GeO₃ as a new type of high‐performance anode for lithium‐ion batteries is reported. The Li₂GeO₃ exhibits a unique porous architecture consisting of micrometer‐sized clusters (secondary particles) composed of numerous nanoparticles (primary particles) and can be used directly without further carbon coating which is a common exercise for most electrode materials. The new anode displays superior cycling stability with a retained charge capacity of 725 mAh g^?1 after 300 cycles at 50 mA g^?1. The electrode also offers excellent rate capability with a capacity recovery of 810 mAh g^?1 (94 % retention) after 35 cycles of ascending steps of current in the range of 25–800 mA g^?1 and finally back to 25 mA g^?1. This work emphasizes the importance of exploring new electrode materials without carbon coating as carbon‐coated materials demonstrate several drawbacks in full devices. Therefore, this study provides a method and a new type of anode with high reversibility and long cycle stability.     

Synthesis,characterization, and thin‐film properties of 6‐oxoverdazyl polymers prepared by ring‐opening metathesis polymerization

Redox‐active 6‐oxoverdazyl polymers were synthesized via ring‐opening metathesis polymerization (ROMP) and their solution, bulk, and thin‐film properties investigated. Detailed studies of the ROMP method employed confirmed that stable radical polymers with controlled molecular weights and narrow molecular weight distributions (Ð < 1.2) were produced. Thermal gravimetric analysis of a representative example of the title polymers demonstrated stability up to 190 °C, while differential scanning calorimetry studies revealed a glass transition temperature of 152 °C. Comparison of the spectra of 6‐oxoverdazyl monomer 12 and polymer 13 , including FT‐IR, UV‐vis absorption, and electron paramagnetic resonance spectroscopy, was used to confirm the tolerance of the ROMP mechanism for the 6‐oxoverdazyl radical both qualitatively and quantitatively. Cyclic voltammetry studies demonstrated the ambipolar redox properties of polymer 13 (E_1/2,ox = 0.25 and E_1/2,red = ?1.35 V relative to ferrocene/ferrocenium), which were consistent with those of monomer 12 . The charge transport properties of thin films of polymer 13 were studied before and after a potential of 5 V was applied, revealing a drastic drop in the resistivity from 10⁶?10¹⁰ Ω m or more to 1.7 × 10⁴ Ω m and suggesting the potential usefulness of polymer 13 in bistable electronics. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1803–1813     

Core‐stabilized polymeric micelle as potential drug carrier: increased solubilization of taxol

Poly(ethylene glycol‐b‐lactide) possessing a methoxy group at the poly(ethylene glycol) (PEG) chain end and a polymerizable methacryloyl group at the poly(lactic acid) (PLA) chain end (MeO–PEG/PLA–methacryloyl) was prepared by an anionic ring‐opening polymerization of ethylene oxide and DL ‐lactide in tandem manner initiated with a potassium 2‐methoxyethanolate, followed by end‐capping with an excess of methacrylic anhydride. The molecular weight of the obtained polymer was controlled by the initial monomer/initiator ratio, which was confirmed by the combination of gel permeation chromatography and nuclear magnetic resonance analyses. The functionality of the methacryloyl–PLA end was almost quantitative. The MeO–PEG/PLA–methacryloyl (38/35; these numbers in parentheses denote the molecular weights of PEG and PLA segments divided by 100, respectively) formed a core–shell type spherical micelle in aqueous media obtained by a dialysis technique, the cumulant diameter of which was ca. 30 nm with very low polydispersity factor. The methacryloyl group adjacent to the PLA was polymerized in the PLA core of the micelle. The polymerization proceeded thermally with radical initiator and photochemically with photo‐initiator to produce core‐polymerized nanoparticles, which was found by spectroscopic and light‐scattering techniques. Taxol‐incorporated micelles were prepared to entrap Taxol into MeO–PEG/PLA–methyacryloyl block copolymer micelles by the oil/water emulsion method. Copyright © 1999 John Wiley & Sons, Ltd.     

Modeling stable free-radical polymerization

A kinetic model has been developed for stable free-radical polymerization (SFRP) processes by using the method of moments. This model predicts monomer conversion, number-average molecular weight, and polydispersity of molecular weight distribution. The effects of the concentrations of initiator, stable radical, and monomer, as well as the rate constants of initiation, propagation, termination, transfer, and the equilibrium constant between active and dormant species, are systematically investigated by using this model. It is shown that the ideal living-radical polymerization having a linear relationship between number-average molecular weight and conversion and a polydispersity close to unity is the result of fast initiation, slow propagation, absence of radical termination, and a high level of dormant species. Increasing stable radical concentration helps to reduce polydispersity but also decreases polymerization rate. Thermal initiation significantly broadens molecular weight distribution. Without the formation of dormant species, the model predicts a conventional free-radical polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2692–2704, 1999