Synthesis and surface chemistry of nano silver particles

In this report, we present a simple wet chemical route to synthesize nano-sized silver particles, and their surface properties are discussed in detail. Silver nano particles of the size 40–80 nm are formed in the process of oxidation of glucose to gluconic acid by amine in the presence of silver nitrate, and the gluconic acid caps the nano silver particle. The presence of gluconic acid on the surface of nano silver particles was confirmed by XPS and FTIR studies. As the nano silver particle is encapsulated by gluconic acid, there was no surface oxidation, as confirmed by XPS studies. The nano silver particles have also been studied for their formation, structure, morphology and size using UV–Visible spectroscopy, XRD and SEM. Further, the antibacterial properties of these nano particles show promising results for E. Coli. The influence of the alkaline medium towards the particle size and yield was also studied by measuring the pH of the reaction for DEA, NaOH and Na₂CO₃.     

Effect of poly(butylene succinate) crystals on spherulitic growth of poly(ethylene oxide) in binary blends of the two substances

The effects of the lamellar growth direction, extinction rings, and spherulitic boundaries of poly(butylene succinate) (PBSU) on the spherulitic growth of poly(ethylene oxide) (PEO) were investigated in miscible blends of the two crystalline polymers. In the crystallization process from a homogeneous melt, PBSU first developed volume‐filling spherulites, and then PEO spherulites nucleated and grew inside the PBSU spherulites. The lamellar growth direction of PEO was identical with that of PBSU even when the PBSU content was about 5 wt %. PEO, which intrinsically does not exhibit banded spherulites, showed apparent extinction rings inside the banded spherulites of PBSU. The growth rate of a PEO spherulite, G_PEO, was influenced not only by the blend composition and the crystallization temperature of PEO, but also by the growth direction with respect to PBSU lamellae, the boundaries of PBSU spherulites, and the crystallization temperature of PBSU, T_PBSU. The value of G_PEO first increased with decreasing T_PBSU when a PEO spherulite grew inside a single PBSU spherulite. Then, G_PEO decreased when T_PBSU was further decreased and a PEO spherulite grew through many tiny PBSU spherulites. This behavior was discussed based on the aforementioned factors affecting G_PEO. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 539–547, 2009     

Efficient synthesis of highly functionalized vinylogous thiol esters

A series of vinylogous thiol esters 2,3 and 2,6-dioxo-1,2,5,6-tetrahydropyridines (cyclic vinylogous thiol esters) 4 were prepared in high to excellent yields from the tandem reaction of readily available α-alkenoylketene diethylthioacetals 1 and diethyl malonate. A plausible mechanism, which involves a base catalyzed retro-Michael ring opening of cyclohexanenes 2 to give vinylogous thiol ester 3, is disclosed.     

Synthesis of β-aminovinylphosphonates by organocatalytic nucleophilic displacement of acetate with amines

The synthesis of diethyl β-aminovinylphosphonates 2 from acetoxy phosphonate 1 is described. The reaction entails an organocatalyzed substitution of the acetoxy group by primary or secondary amines. The use of a catalytic amount of DABCO is necessary if the amine is not nucleophilic enough, otherwise a strong nucleophilic amine can react without organocatalyst. The reaction led to a series of functionalized title compounds in good to excellent yields.     

Novel poly(butylene succinate-co-lactic acid) copolyesters: Synthesis, crystallization, and enzymatic degradation

A series of aliphatic biodegradable poly(butylene succinate-co-dl-lactide) (PBSLA) copolyesters were synthesized with the aim of improving the degradation rate of poly(butylene succinate) (PBS) by incorporation of dl-oligo(lactic acid) (OLA) into the PBS molecular chains. The composition and sequential structure of the aliphatic copolyesters were investigated by proton nuclear magnetic resonance (¹H NMR) spectroscopy. The crystallization behaviors, the crystal structure and morphology of the copolyesters were investigated by using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarizing optical microscopy (POM), respectively. The results indicate that the crystallization of the copolyesters was restricted by the incorporation of lactide (LA) units, which further tuned the mechanical properties of the copolyesters. The copolyesters could form complete spherulites and exhibit the same crystal structure as that of PBS. Enzymatic study indicated that the copolyesters with higher content of LA units degraded faster, and the degradation began in the amorphous regions and then in the crystalline regions. The morphology and the resulting degradation products of the copolyesters were investigated by scanning electron microscopy (SEM) and ¹H NMR analysis during the degradation process.     

Selective synthesis of mono- and distannylpyridines from chloropyridinols via an SRN1 mechanism

A selective two-step synthesis of either mono- or distannylated pyridines from commercially available pyridinols, involving its conversion to the corresponding diethyl pyridyl phosphates (pyDEP) followed by the reaction with Me₃SnNa in liquid ammonia, is described.The results obtained clearly indicate that the reactions proceed through an unimolecular radical nucleophilic substitution mechanism (S_RN1) with intermediacy of a monosubstitution product.     

Multiply ionization of diethyl ether clusters by 532 nm nanosecond laser: The influence of laser intensity and the electron energy distribution

The formation mechanism for multiply charged ions (C^q+ and O^q+ (q = 2–4)) were investigated using a dual polarity time-of-flight mass spectrometer when diethyl ether clusters interacted with nanosecond laser pulse. The signal intensity of multiply charged ions and electron energy was measured experimentally. It was shown that the intensity of multiply charged ions increased about 50 times when laser intensity increased from 7.6 × 10⁹ to 7.0 × 10¹⁰ W/cm², then saturated as laser intensity increased further. It is interesting that the evolution of the mean value of electron energy was same to that of multiply charged ions. The theoretical calculation showed the ionization potential of atomic ions could be significantly decreased due to the effect of Coulomb screening especially at low laser intensity. It indicated that the electron ionization combined with Coulomb screening effect could explain the production of multiply charged ions in nanosecond laser field.     

丁二酸二油酯磺酸钠合成及纯化方法的改进

研究了丁二酸二油酯磺酸钠合成及纯化方法的改进，使其产率由30％提高到了80．9％。     

CAN Catalyzed One‐Pot Synthesis of α‐Amino Phosphonates from Carbonyl Compounds

Abstract

α‐Amino phosphonates are synthesized by three component condensation of aldehydes, amines, and diethyl phosphite using ceric ammonium nitrate at room temperature to afford the corresponding α‐amino phosphonates in high yields.     

Preparation of Starch Succinate WITH INTERMEDIATE DS BY AQUEOUS SLURRY REACTION

Modification of starch by chemical derivatization has been widely studied since early 1950s. The formation of starch ester such as acetate and propionate imparts starch water resistance. In contrast, the introduction of carboxylates onto starch increases the hydrophilicity of starch. One example is carboxymethyl starch (CMC), which has been widely used in several industry areas. Succinic anhydride reacts with starch to form starch succinates. Since starch succinates are polyanions, they off…