Preparation of Dendritic Carbosilane-supported Palladium Catalyst and Its Catalytic Activity in Hydrogenation of Organic Compounds

A great deal of interest has been shown in the field of dendrimer during the past decade1-10.Among the main potential applications of dendrimer,catalysis stands as one of the most promising applications,because dendrimers offer a unique opportunity to combine the advantages of homogeneous and heterogeneous catalysis11.It is possible to change the structure,size,and solubility of dendrimers and metallodendrimers at will12.It has been demonstrated that this metallodendritic catalyst is possible …     

PAMAM树形分子为模板低温制备纳米硫化锌空心球

Hollow ZnS spheres have been prepared in the presence of generation 3.5 poly (amidoamine) dendrimers with surface ester groups (G3.5-COOCH3 PAMAM dendrimer) as synthetic matrix template. The products obtained were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis absorption. TEM studies show that the hollow spheres with diameters ranging from 80 to 100 nm are prepared. The range of wall thickness was estimated to be about 20～30 nm. It was found that the concentration of PAMAM dendrimer had a significant influence on the formation of hollow ZnS spheres. The possible formation mechanism of the hollow spherical structure is also discussed.     

Synthesis and Properties of a Biodegradable Dendritic Magnetic Resonance Imaging Contrast Agent

Novel biodegradable dendritic contrast agents (DCAs) based on polyester dendrimers were synthesized and characterized.The DCAs were stable at acidic pH,but hydrolyzed rapidly at physiological pH,which rendered the DCA's long-term Gd3+ retention as low as that of small molecule CAs.Their longitudinal relaxivities of 10.2 to 17.5 L·mmol-1·s-1 were about 2.4 to 4.1 times higher than that of DTPA-Gd,indicating their superior contrast-enhancing capability to the clinically used contrast agent.The in vivo MRI study suggested that the DCA at lower generation (G2-DTPA-Gd) could effectively enhance the MRI of tumor,while the one at higher generation (G5-DTPA-Gd) showed more potential in liver imaging.     

银离子与聚酰胺-胺型树形高分子配位作用的研究

The complexation between poly(amidoamine) (PAMAM) dendrimers and silver ion was studied in this paper. The results showed that generations and surface groups of dendrimers， reaction time， pH value， mole ratio of Ag⁺/PAMAM dendrimers， as well as reaction temperature strongly influence complexation between Ag⁺ and PAMAM dendrimers. The maximum complexing number of Ag⁺ that amino-， hydroxyl- and carboxylate- terminated PAMAM dendrimers could bind has been obtained. It has been found that the measured value of amino- and hydroxyl- ter-minated PAMAM is almost similar to the theory value， but to carboxylate- terminated PAMAM， there is a dis-crepancy between the measured value and theory value because of the electrostatic interaction between the silver ion and carboxyl group.     

Synthesis and characterization of carbazole-based dendrimers as bipolar host materials for green phosphorescent organic light emitting diodes

A group of novel, carbazole-based dendrimers comprised of the electron-accepting dibenzothiophene core and the electron-donating oligo-carbazole dendrons, namely G1 SF and G2 SF, are synthesized utilizing the Ullmann C–N coupling reaction. The dendrimers are designed in such a way to show good solubility in common organic solvents, excellent thermochemical stability with decomposition temperatures(Td) up to430 8C, and high HOMO levels in a range from 5.45 e V to 5.37 e V. Results of density functional theory calculations(DFT) indicate G2 SF has an almost complete separation of HOMO and LUMO levels at the holeand electron-transporting moieties; while G1 SF exhibits only partial separation of the HOMO and LUMO levels possibly due to intramolecular charge transfer. Green phosphorescent OLEDs were fabricated by the spin coating method with the dendrimers as hosts and traditional green iridium phosphor as doped emitter. Under ambient conditions, a maximum luminance efficiency(hL) of 19.83 cd A~-(1)and a maximum external quantum efficiency of 5.85% are achieved for G1 SF, and 15.50 cd A (-1)and 4.57% for G2 SF.     

Analyzing solubility of acid gas and light alkanes in triethylene glycol

Physical solvents such as ethylene glycol （EG）, diethylene glycol （DEG）, and triethylene glycol （TEG） are commonly used in wet gas dehydration processes with TEG being the most popular due to ease of regeneration and low solvent losses. Unfortunately, TEG absorbs significantly more hydrocarbons and acid gases than EG or DEG. Quantifying this amount of absorption is therefore critical in order to minimize hydrocarbon losses or to optimize hydrocarbon recovery depending on the objective of the process. In this article, a new correlation that fully covers the operating ranges of TEG dehydration units is developed in order to determine the solubility of light alkanes and acid gases in TEG solvent. The influence of several parameters on hydrocarbon and acid gas solubility including temperature, pressure, and solvent content is also examined.     

Fabrication of Dendrimer－like PAMAM Based on Silica Nanoparticles

A G 4.0 dendrimer-like poly (amido amine) (PAMAM) based on silica nanoparticles was fabricated via a divergent approach.It was built from γ-aminopropyi silica nanoparfides (APSN) core via repetitive addition of acrylate (MA) and hexylenediamine (HDA). FT-IR and EA were used to monitor the progress of dendrimer during each step. The amino group content of the resulting product increased from 0.49 to 3.72 mmol/g after the 4th generation. In addition, the percentage of grafting increased with increasing generation and reached to 65.9% after 4th generation. It was found that the resulting silica nanoparticles could be dispersed in methanol with a mean hydrodynamic particle diameter of 152.7 nm although the silica nanoparticles had agglomerated during the storage period.     

Dendronized Polymers with High FTC-chromophore Loading Density:Large Second-order Nonlinear Optical Effects,Good Temporal and Thermal Stability

In this study,two new dendronized nonlinear optical(NLO)polymers were synthesized with high FTC chromophore loading density by introduction of high generation chromophore dendrons on the side chains.Due to their suitable molecular weights,both of them possessed good solubility in common solvents.They also inherited the advantages of dendrimers(large NLO coefficient),especially for PG2 whose NLO coefficient d33 value was as high as 282 pm·V^–1.Also,PG2 had a good temporal stability with 80%of its maximum value being retained at the temperature as high as 129℃.     

A reactive oxygen species-responsive dendrimer with low cytotoxicity for efficient and targeted gene delivery

Nonviral vectors have been attracting more attention for several advantages in gene delivery and the development of nonviral gene ca rriers with high delivery efficiency and low cytotoxicity has long been a key project.Starburst polyamidoamine dendrimers are a class of synthetic polymers with unique structural and physical characteristics.However,when they are used as gene carrier,the gene transfection efficiency is not satisfactory.Herein,a novel thioketal-core polyamidoamine dendrimer(i.e.,ROS-PAMAM)was synthesized and characterized.Compared to ethylenediamine-core dendrimers or widely used cationic polymers of polyetherimide,ROS-PAMAM showed lower cytotoxicity.Moreover,ROS-PAMAM demonstrated reactive oxygen species responsive characteristics,which can facilitate the release of siRNA in the tumor microenvironment.In vitro gene transfection experiments based on A549 cells confirmed that siRNA/ROS-PAMAM exhibits high gene transfection efficiency.It is concluded that ROS-PAMAM shows great potential as a generalizable vehicle for gene therapy applications.     

Alkoxy encapsulation of carbazole-based thermally activated delayed fluorescent dendrimers for highly efficient solution-processed organic light-emitting diodes

Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent(TADF) emitters(namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via C—N coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core.It is found that,compa red with the commo nly-used tert-butyl groups,the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers,producing stronger TADF effect together with faster reverse intersystem crossing process.Solution-processed TADF organic light-emitting diodes(OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%,respectively,which are ～1.6 and～2.0 times that of the tert-butyl-encapsulated counterparts.These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.     

Aliphatic Hyperbranched Poly（amido amine）s （PAMAMs） ： Preparation and Modification

A series of water soluble aliphatic hyperbranched poly(amido amine)s(PAMAMs) with the same or similar chemical structure of poly(amido amine) dendrimer was successfully synthesized from commercially available AB and Cn types of monomers by one-pot polymerization via the couple-monomer methodology(CMM). The AB type monomer used in this paper was methyl acrylate, and Cn monomers were multi-amino compounds such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetraamine (TETA). tetraethylenepentaamine (TEPA) and pentaethylenehexamine (PEHA). The reaction mechanism was investigated by means of the mass spectra of the reaction intermediates. Adjusting the feed ratio of AB to Cn. hyperbranched polymers with different terminal groups and properties were obtained. FTIR, NMR, DSC. and TGA were used to characterize the polymers. It was found that the polymers‘ properties such as solubility, thermal behaviour and encapsulation capability varied with changing the feed ratio of AB to Cn. Benzoyl and palmitoyl groups were introduced into these macromolecules by acidylation to form amphiphilic hyperbranched polymers which have a high capability to encapsulate water soluble dyes such as Congo red. It is expected that the hyperbranched PAMAMs can play an important role in the industrial applications, such as coatings, cross-linking and phase-transferring agents because of their versatility and availability.     

Reverse-phase high-performance liquid chromatography of virus proteins and other hydrophobic proteins

Summary So far most solvents generally used in reverse phase chromatography (RPC) for separation of peptides and water soluble polypeptides could not be utilized for hydrophobic proteins such as membrane proteins and structural polypeptides of viruses due to their insufficient solubility. But we have introduced a new RP-HPLC solvent system which was very useful in our studies on poliovirus polypeptides. Formic acid in high concentration is an extremely potent solvent for proteins, particularly those that are hydrophobic. Preliminary estimates are made of the concentration of formic acid which is required to completely dissolve hydrophobic proteins. For example, solubilization of structural polypeptides of poliovirus which are absolutely water insoluble requires 60% formic acid. Therefore, we used a proportion of 60% formic acid in all solvents for reversed phase chromatography and applied propanol-2 or acetonitrile as the organic modifiers for gradient elution. Using this mobile phase all four poliovirus polypeptides of three serological types were obtained in high purity by this rapid procedure. In each case, polypeptides were quantitatively eluted independent of the amount of protein (1–1000 μg) injected onto the columns. The solvents used were volatile and easily removed in a short evaporation step. Therefore this solvent system is suited for analytical and for micropreparative separation of proteins for chemical, biochemical and immunological studies. Rechromatography and electrophoresis in SDS-polyacrylamide gels of the separated polypeptides demonstrated that this solvent system with its high proportion of formic acid did not alter their primary structure. There may have been major changes in secondary and tertiary structure. In contrast, alterations of the elution characteristics were observed after reduction of disulfide bridges and several modifications of proteins. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Application of Single—labelled Probe—primer in PCR Amplification to the Detection of Hepatitis B Virus DNA

A new method based on the incorporation of a single-lablled probe-primer into polymerase chain reaction(PCR) for the detection of PCR-amplified DNA in a closed system is reported.The probeprimerc consists of a specific probe sequence on the 5‘‘‘‘‘‘‘‘-end and a primer sequence on the 3‘‘‘‘‘‘‘‘-end.A flurophore is located at the 5‘‘‘‘‘‘‘‘end.The primeR-quencher is an oligonucleotide,which is complementary to the probe sequence of probe-primer and labelled with a quencher at the 3‘‘‘‘‘‘‘‘-end.In the duplex formed by probe-primer and primer-quencher.the fluorophore and quencher are kept in close proximity to each other.Therefore the fluorescence is quenched.During PCR amplificatio,the specific probe sequence of probeprimer binds to its complement within the same strand of DNA,and is cleaved by Taq DNA polymerase,resulting in the restoration of fluorescence.This system has the same energy transfer mechanism as molecular beacons,and a good quenching effciency can be ensured.Following optimization of PCR conditions,this method was used to detect hepatitis b virus(HBV) dna in patient sera.This technology eliminates the risk of carry-over contamination,simplifies the amplification assay and opens up new possibilities for the real-time detection of the amplified DNA.     

Performance enhancement of phosphoric acid fuel cell using phosphosilicate gel based electrolyte

Replacement of phosphoric acid electrolyte by phosphosilicate gel based electrolytes is proposed for performance enhancement of phosphoric acid fuel cell(PAFC).Phosphosilicate gel in paste form and in powder form is synthesized from tetraethoxysilane and orthophosphoric acid using sol-gel method for two different P/Si ratio of 5 and 1.5 respectively.Replacement of phosphoric acid electrolyte by phosphosilicate gel paste enhances the peak power generation of the fuel cell by 133% at 120 ℃ cell temperature;increases the voltage generation in the ohmic regime and extends the maximum possible load current.Polyinyl alcohol(PVA) is used to bind the phosphosilicate gel powder and to form the hybrid crosslinked gel polymer electrolyte membrane.Soaking the membrane with phosphoric acid solution,instead of that with water improves the proton conductivity of the membrane,enhances the voltage and power generation by the fuel cell and extends the maximum possible operating temperature.At lower operating temperature of 70 ℃,peak power produced by phosphosilicate gel polymer electrolyte membrane fuel cell(PGMFC) is increased by 40% compared to that generated by phosphoric acid fuel cell(PAFC).However,the performance of composite membrane diminishes as the cell temperature increases.Thus phosphosilicate gel in paste form is found to be a good alternative of phosphoric acid electrolyte at medium operating temperature range while phosphosilicate gel-PVA composite offers performance enhancement at low operating temperatures.     

外围含对-硝基偶氮苯介晶基团的椭球型硅碳烷树状物

Novel carbosilane liquid crystalline dendrimers based on 1,6-hexanediol were prepared. Using the precursors Gn-C1 （n = 1-3） with Si-C1 bonds on the periphery as dendritic scaffolds and 4-[4-（6-hydroxyhexyloxy）phenylazo]- nitrobenzene as mesogenic group, a series of carbosilane liquid crystalline dendrimers from the first to the third generation were synthesized. These carbosilane liquid crystalline dendrimers showed smectic phase.     

Synthesis of Novel Carbosilane Dendrimers with Myo—inositol Cores

The preparation of carbosilane dendrimers with cores of myo-inositol and the outmost periphery grougs of allyl groups has been reported.By using alternate hydrosilylation and alkenyiation reactions,the dendrimer have been carried up to the third generation with 48 allyl groups on the periphery.     

New materials based on carbazole for optoelectronic device applications：Theoretical investigation

A quantum-chemical investigation on the structural and optoelectronic properties of two materials based on carbazole is carried out.The purpose is to display the effect of grafting the fluorine atoms on their optoelectronic and physico-chemical properties.In addition to solubility in the polar solvents and the modification in geometric parameters,the substitution of fluorine destabilizes the HOMO and LUMO levels,decreases the band gap energy and raises conjugation length.These properties suggest the substituted fluorine compound as a good candidate for optoelectronic applications.     

Theoretical Investigation of Nonlinear Optical Properties of Organic and Transition Metal Hybrid Azobenzene Dendrimers

In this work, we report a theoretical exploration of the responses of organic azobenzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers （GO）, and the first, second and third generation （G1, G2 and G3, respectively） are investigated by semi-empirical methods. The calculated results show that the nonlinear optical （NLO） properties of these organic dendrimers are mainly determined by the azobenzene chromospheres. Additionally, the values oft and y increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers （core-hybrid and branch-end hybrid according to the sites combined with transition metals） are simulated and discussed in detail in the framework of time-dependent density functional theory （TDDFT）. The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.     

乙醇在新型Mo/C催化剂上的气相羰基化反应

The carbonylation of alcohol to acid or ester is an important process in the chemical industry. The Monsanto process for acetic acid via the homoge neous carbonylation of methanol is an example of the largest scale commercial application of this route[1].Recently, ethanol carbonylation for manufacturing propionic acid and ethyl propionate became an at tractive approach, and many research efforts were made for an appropriate catalyst to carry out the va por phase carbonylation under atmospheric pres sure[2～4]. Although an iodide-promoted Ni/C cata lyst is found to exhibit satisfactory activity and se lectivity for the vapor phase carbonylation of ethanol, it is affected by the disadvantages associat ed with a highly corrosive reaction medium and dif ficult product separation owing to the use of ethyl iodide as promoter. There has been little success in finding heterogeneous or homogeneous catalyst that can operate effectively without a halide promoter[5].