Poly(amidoamine) dendrimers with phenyl shells: fluorescence and aggregation behavior

The fluorescence and aggregation behavior of poly(amidoamine) (PAMAM) dendrimers modified with phenyl groups at the periphery (PAMAM-P) were investigated. For comparison, the third generation (G3) PAMAM dendrimer with a shell of positive charge (PAMAM-PA) was also synthesized. PAMAM-P G3, G4 and G5 show dual fluorescence emission due to the fluorescence emission of phenyl ring and its excimer. By increasing the generation number from G2 to G4, the fluorescence intensity of phenyl ring decreases, and the fluorescence of phenyl excimer appears and becomes obvious. The three-dimensional geometry arrangement or dendrimer architecture was found to have a strong effect on their fluorescence behavior. This result is further supported by the solvent effect and model compound studies. The lower generations (PAMAM-P G0 to G3) were self-organized into spherical aggregates. However, no aggregation behavior was observed for the higher generations (>G3). The critical aggregation concentration (CAC) values measured by fluorescence spectroscopy were found to decrease gradually with increasing generation number from G0 to G3.     

酸碱滴定分析在聚酰胺-胺表征中的应用

整数代聚酰胺-胺(PAMAM)树形分子含有末端伯胺基及内部有叔胺基,酸碱滴定分析可以表征伯胺基及叔胺基的数量。文中详细讨论了该方法的原理,说明滴定过程中产生的酰胺键水解不影响滴定及计算结果。滴定分析在不同初始pH条件下进行,通过实验表明,在pH<2的条件下滴定可以保证叔胺的充分质子化。     

Spectroelectrochemical analysis of ion-transfer and adsorption of the PAMAM dendrimer at a polarized liquid|liquid interface

The interfacial behavior of the fourth generation polyamidoamine (G4 PAMAM) dendrimer at a water|1,2-dichloroethane (DCE) interface was studied by cyclic voltammetry and potential modulated fluorescence (PMF) spectroscopy. Irregular voltammetric responses were observed at positively polarized interfaces. The cyclic voltammogram was strongly dependent on pH and on the concentrations of the G4 PAMAM dendrimer and the organic supporting electrolyte. PMF spectroscopy was successfully used to analyze the interfacial mechanism of the dendrimer by adding an anionic porphyrin derivative as a fluorescent probe. The results of the PMF measurements demonstrated that the G4 PAMAM dendrimer was transferred across the interface, a process that was accompanied by an adsorption step at pH 7. In contrast, under alkaline conditions, the adsorption process did not seem to be involved in the interfacial behavior.     

Water-soluble porphyrin-PAMAM-conjugates of melphalan and their anticancer activity

p-[bis(chloro-2-ethyl)amino]-L-phenylalanine (melphalan) is an approved anti-cancer agent with a broad spectrum of antitumor activity. However, it has some disadvantages, such as poor water-solubility followed by rapid elimination, which reduce the target specificity. To solve these problems, porphyrin- poly(amidoamine) or PAMAM-conjugates of melphalan were synthesized and characterized. The dendrimeric conjugates showed satisfactory water solubility. It was found that the size of the dendrimer played a crucial role in controlling the drug content and diameter of the melphalan-conjugates. The in vitro studies of cell cytotoxicity revealed that by employing the dendrimeric conjugation strategy and using the PAMAM dendritic arms as spacers, the conjugates had good anti-cancer activity and lower toxicity than free melphalan.     

环氧基POSS/PAMAM杂合材料的制备及性能研究

以3-缩水甘油基氧丙基三甲氧基硅烷(EPTMS)为原料,合成得到了八官能团缩水甘油醚-多面体低聚倍半硅氧烷(简称POSS-EP)。采用4代树型端氨基聚酰胺-胺(PAMAM)作为POSS-EP和双酚A型环氧树脂(DGEBA)共混物的固化剂,制备了5个环氧基POSS/PAMAM杂化材料。通过动态差示扫描量热仪(DSC),研究了环氧和PAMAM的固化反应动力学。通过DSC、热重分析(TGA)、拉力和冲击测试,对环氧基POSS/PAMAM杂化材料的热性能和力学性能进行了研究。结果表明,该环氧基POSS/PAMAM杂化材料具有优良的热性能和力学性能。     

含1,3,5-三嗪核结构的新型聚酰胺(PAMAM)树枝状化合物的合成

以2,4,6,三氯-1,3,5-三嗪为核(GO)与亚胺基二乙酸二乙酯进行取代反应制得具有枝化的含有酯基官能团的树枝状化合物(G0.5),然后依次与乙二胺、丙烯酸甲酯和乙二胺反应分别制得含有1,3,5-三嗪核的G1.0、G1.5和G2.0代的树枝状化合物.采用FT-IR、1HNMR、13CNMR和ESI-MS对所合成的化...     

荧光性聚酰胺-胺树形分子在潜指纹显现中的应用研究

本文系统研究了不同条件(树形分子代数、浓度、浸泡时间等)下荧光性聚酰胺-胺树形分子(PAMAM)水溶液作为荧光探针对锡纸、透明胶带等基底上油印潜指纹的显现效果.结果发现PAMAM树形分子可以和指纹残留物进行靶向结合.结合到指纹纹线上的该荧光性纳米材料在暗室中365 nm紫外光的激发下发出明亮的蓝色荧光,指印纹线与基底反差大、指纹易于辨认,且操作简单,试剂完全环保无污染.这些结果表明PAMAM水溶液是一种潜在的优良的指纹显现试剂.最后,把PAMAM树形分子水溶液对指纹的显现效果进行量化处理,乳突纹与基底间的灰度对比度达到90%以上.     

Enhanced Electrocatalysis for Methanol Oxidation on Ordered {[PdPW11O39]5–/Pt/PAMAM}n Multilayer Composites

The {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}_n multilayer composites constructed from G4.0 Amino‐terminated poly (amidoamine) dendrimer (PAMAM), Pt and Keggin‐type palladium(II)‐substituted polyoxometalates anion ([PdPW₁₁O₃₉]^5–) were prepared via layer by layer electro‐depositing technique. The X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and field emission scanning electron microscope (FE‐SEM) characterization indicate that the Pt nanoparticles have been anchored on the as‐prepared nanocomposites. And the morphologies of Pt nanoparticles are influenced by deposition potential, the number of layers of {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}_n multilayer nanocomposites, and the existence of PAMAM. The electrocatalytic properties and stability of {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}_n multilayer nanocomposites were investigated by cyclic voltammetry. Experimental investigation results reveal that PAMAM is a good support for Pt nanoparticle growth due to its interior cavity structure and high stability. [PdPW₁₁O₃₉]^5– play an important role to prevent intermediate product (mainly as CO) in the methanol oxidation from poisoning the as‐prepared catalyst. The {[PdPW₁₁O₃₉]^5–/Pt/PAMAM}₃/GC shows better electrocatalytic properties, stability, and CO tolerance ability than Pt/GC and {Pt/PAMAM}₃/GC fabricated by similar electrodeposition processes.     

Preparation of catalytic films of platinum on Au substrates modified by self-assembled PAMAM dendrimer monolayers

In this work we demonstrate the preparation of highly catalytically active Pt formed by the galvanic replacement of the copper adlayer on Au substrates, modified by the self-assembly of fourth generation amine terminated PAMAM dendrimer (G4NH₂). The copper adlayer was formed on the dendrimer-modified gold substrate by chemical preconcentration of copper ions followed by electrochemical reduction. The Pt overlayer was characterized by SEM, XPS and by cyclic voltammetry. The catalytic efficiency of the modified film thus prepared through soft route was evaluated by the electro catalytic oxidation of methanol using cyclic voltammetry, chronoamperometry and AC impedance techniques. This work also demonstrates that the copper adlayer formed on the dendrimer-modified electrode can undergo galvanic replacement by nobler metals like Au and Ag, besides Pt. An elegant soft route involving a new three-step protocol to build the concentration of active Pt on the Au surface has been developed. Concentration of the same metal (Pt) or two different metals (Pt–Au) can be built at the interface in a stepwise manner at ambient temperature.     

Synthesis and antioxidant activities in polyolefin of dendritic antioxidants with hindered phenolic groups and tertiary amine

Two novel primary antioxidants with dendritic structure and hindered phenolic groups were synthesized using 3‐(3,5‐diter‐butyl‐4‐hydroxyphenyl) propionic acid as raw material and dendritic poly(amidoamine) (PAMAM) as linker in chloroform. The antioxidant activities of the dendritic antioxidants were evaluated in polyolefin by melt flow index (MFI), yellowness index (Y.I.), and oxidation induction time (OIT). The dendritic antioxidants had excellent processing property and oxidation resistance behavior in polyolefin. At the same weighed amount of antioxidant, the MFI and Y.I. values of mulitiple‐extruded polyethylene (PE) stabilized with the dendritic antioxidants were smaller than those of the commercial antioxidants, as well as the OIT values of polyethylene (PE) stabilized with the dendritic antioxidants were larger. Applying to polypropylene, the antioxidant ability of the second‐generation dendritic antioxidant (G2.0 dendritic antioxidant) with larger molecular weight was superior to the commercial antioxidants and that of the first‐generation dendritic antioxidant (G1.0 dendritic antioxidant) was equal to the commercial antioxidants. The dendritic antioxidants can prevent polyolefin from breaking of macromolecular chain in processing and had stabilizing effect in polyolefin in service life by donating H‐atoms and electron to free radicals. The dendritic antioxidants combined with Irgafos 168 had improvement of antioxidant activities of the dendritic antioxidants in polyolefin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012