Oxygen reduction and diffusion in electroactive nanostructured membranes (ENM) using a layer-by-layer dendrimer-gold nanoparticle approach

The fabrication of an electroactive nanostructured membrane (ENM) for oxygen reduction, made of layer-by-layer (LbL) films comprising Au nanoparticle-containing amine-terminated G4 PAMAM dendrimer alternated with poly(vinylsulfonic acid) (PVS) layers is reported. Electrochemical impedance spectroscopy and cyclic voltammetry show that electrodes with PVS/PAMAM-Au multiple bilayers are efficient for oxygen reduction and diffusion. A linear increase of oxygen reduction current occurs for up to 3 bilayers, with no further significant increase occurring for more than 3 bilayers. The 3-bilayer PVS/PAMAM-Au electrode, as an Au-ENM, is an attractive new system with potential for building diverse electrocatalytic devices with high molecular control.     

树枝状聚酰胺胺与线形聚合物共混的研究

介绍了聚酰胺胺(PAMAM)树状分子的独特结构和性能,综述了国内外有关聚酰胺胺树状分子与线形聚合物共混的研究进展。参考文献24篇,包括树枝状聚酰胺胺的分子结构,它的性能及其同PHE-MA、PVC、PVC和PVAC,尼龙6、聚马来酸酐、聚甲基乙烯基醚、环氧树脂等共混物。     

树形高分子增强的高分子磁性颗粒的制备与表征

利用化学共沉淀法制备Fe3O4磁性纳米粒子;悬浮聚合的方法制备带有酰胺基的聚苯乙烯-丙烯酰胺磁性颗粒(NMP);发散法制备聚酰胺胺树形高分子(PAMAM)并与酰胺修饰聚苯乙烯磁性颗粒结合,得到树形高分子增强的磁性微粒。并对NMP和PAMAM-NMP的颗粒基质晶体结构、饱和磁化强度、表面官能团和微观结构以及各元素的百分含量进行表征。结果显示,Fe3O4磁核晶形完整,平均粒径为9 nm;PAMAM-NMP的红外图谱在3478 cm-1和3 300 cm-1处有吸收峰,证明存在胺基;经PAMAM增强后氮元素百分含量由0.225%增加到0.992%,证明PAMAM为NMP提供了更多的活性基团;在有无磁场存在时的沉淀时间分别为16 h和2112 h,证明PAMAM-NMP有良好的磁响应性和悬浮性。     

Thermo- and pH-sensitive dendrimer derivatives with a shell of poly(N,N-dimethylaminoethyl methacrylate) and study of their controlled drug release behavior

Novel dendrimer derivatives combining the temperature- and pH-sensitivities are synthesized. At first, polyamidoamine (PAMAM) dendrimers with generations 1-5 are synthesized by the reaction of ethylenediamine with methyl acrylate, and then the dendrimers are acylated by chloroacetyl chloride to obtain PAMAM-Cl, which can act as a macroinitiator for further synthesizing functional dendrimers. For fulfilling this goal, the polymers consisting of a dendritic PAMAM core and poly(N,N-dimethylaminoethyl methacrylate) (PDMA) shell are synthesized by atom transfer radical polymerization (ATRP). Their macromolecular structures are characterized by FTIR, ¹H NMR, DSC and particle size analyses, and their aqueous solutions are inspected by UV spectroscopy for understanding their thermo- and pH-sensitivities. The results show that novel dendrimer derivatives exhibit clearly thermo- and pH-respondings in accordance with the change of the environment. Using chlorambucil (CLB) as a model drug, the behaviors of the controlled drug release from polymers with different average graft length of PDMA are studied. The results indicate that the rate of the drug release can be effectively controlled by the pH value.     

紫外光辐照下以PAMAM树形分子为模板制备Ag纳米簇及光致发光性能研究

以G5．0-OHPAMAM树形分子为模板，用紫外光辐照法制备银纳米簇．用透射电子显微镜、紫外-可见吸收光谱和共振散射光谱等对所制备的银纳米簇进行了表征．结果表明：用紫外光辐照法可以制备尺寸分布均匀、稳定的银纳米簇；且辐照时间、PAMAM树形分子的浓度及Ag^＋／PAMAM树形分子的摩尔比都会对所制备的银纳米簇产生较大的影响．由于所制备的银纳米簇的粒径小于树形分子的流体力学半径，表明树形分子起到了“内模板”作用．同时研究了银纳米簇的尺寸对其光致发光性能的影响，发现通过调节银纳米簇的尺寸可实现其光致发光的可调性．     

聚酰胺胺(PAMAM)树状分子的合成

介绍了聚酰胺胺(PAMAM)树状分子的三种合成方法,即发散合成法、收敛合成法以及发散收敛结合合成法的主要特点及其进展,探讨了各种方法的优缺点。发散合成法具有分子量增长迅速的优点,但是分离纯化步骤多;收敛合成法的特点是分子量分布窄,但是分子量增长慢;发散收敛结合合成法综合了发散合成法和收敛合成法的优点,很有发展前途。同时,提出了PAMAM树状分子合成研究发展方向。     

以酯端基PAMAM树形分子为模板在N，M-二甲基甲酰胺溶剂中制备金纳米粒子

用UV-vis、FT-IR光谱研究了HAuCl4和酯端基聚酰胺胺(PAMAM)树形分子在N，N-二甲基甲酰胺(DMF)溶剂中的相互作用，提出HAuCl4与树形分子之间的络合机理：[AuCl4]^-离子与质子化叔胺基团形成离子对，Au^3 离子与PAMAM树形分子上的酯基和酰胺基团形成配位作用。在DMF溶剂中酯端基PAMAM树形分子与HAuCl4配位后用柠檬酸钠还原形成金纳米粒子，UV-vis光谱和TEM图像分析表明了随树形分子代数的增加，金纳米粒子的直径减小，并提出了树形分子-金纳米复合物的结构模型：(1)较低代数的树形分子环绕在金粒子的外围；(2)在较高代数的树形分子空腔内部封装金纳米粒子。     

萘修饰的树枝形聚酰胺-胺的合成与荧光性质研究

在DMF溶剂中使用不同代数的整代树枝形聚合物聚酰胺-胺(PAMAM)与1,8-萘二甲酸酐进行酰胺化反应,制备了1,8-萘酰亚胺修饰的3.0G以及5.0G的树枝形聚合物D3、D5。对产物进行红外、紫外-可见吸收、荧光发射、激发光谱以及元素分析的表征,产物与目标产物结构一致。在氯仿与乙醇(体积比为1∶1)的混合溶剂中,由于PAMAM对萘环的固定作用,在萘环浓度相同的情况下,1,8-萘二甲酸酐不形成激发态萘环与基态萘环的激基缔合物,而聚合物D形成了分子内萘环的激基缔合物,在471 nm处产生萘环激基缔合物的荧光发射峰,具有潜在的应用价值。     

Study on Interaction Energy of PAMAM/Lanthanide（ Ⅲ ） by Molecular Dynamics Method

PAMAM/lanthanide （Ⅲ） nanocomposite was studied by molecular simulation method. Molecular simulation enabled study of the lanthanide tetrad effect at atomic level. However, PAMAM dendrimer exhibiting unique properties such as nanometer size and highly functionalized terminal surface provided a novel space for lanthanide （Ⅲ） to show their peculiar tetrad effect. The results showed that total energies of PAMAM/lanthanide（Ⅲ） nanocomposites presented obvious tetrad effect and special double-double effect. Nd, Gd, and Er fell to the lower point and Gd fell to the lowest point in the TE-Ln curve with four groups. In order to explain the tetrad effect, kinetic energy （KE） and potential energy （PE） were analyzed. The KE curve consisted of three W-type parts （La - Pm, Pm - Tb, Tb - Tm, and the latter two W-type part were axial symmetry） and an exception part （Yb - Lu）. It also showed that the KE of odd atomic number was higher than the even one＇s with exception of Yb and Lu. Furthermore, decomposed potential energies gave out the atomic-level subtle difference of lanthanide which present more regulations for Eu（Ⅲ） - Lu（Ⅲ） compared with La（Ⅲ） - Sm（Ⅲ）. And also Ho-valley and three platforms （Sm - Eu, Td - Dy, Er - Tm） were discovered that refect the regular change of nanocomposite structures. Additionally, there are distinct correlations between Ebond and EInversion, EAngle and EVDW, Eworsion and ECoul, respectively. Therefore, PAMAM could be used in separation of lanthanide by changing conditions.     

High‐flow nylon 6 by in situ polymerization: Synthesis and characterization

A new synthetic strategy for high‐flow nylon 6 was developed in this article. Generation 1, 2, 3 (G1, G2, G3) polyamidoamine (PAMAM) dendrimers reacted with p‐phthalic acid by equimolar terminal groups in water solution, respectively, and mother salt solution was then prepared. The high‐flow nylon 6 was prepared with suitable quantity of mother salt solution, end‐capping agent, and ?‐caprolactam by in situ polymerization. Blue shifts are found for the peaks of NH (γN? H and 2δN? H) of the high‐flow nylon 6 compared with pure nylon 6 in the IR spectra. Comparing with the pure nylon 6, the high‐flow nylon 6 containing low content of PAMAM units, has high‐flow property and almost the same mechanical property. The high‐flow nylon 6 with low content of PAMAM units has greater melt‐flow index (MFI) (the value of MFI increased by 70–90%). Hardly any decrease in the tensile strength is observed with the elongation at break decreasing by 20–35%. But the izod impact strength of the high‐flow nylon 6 increases. The SEM images show that the high‐flow nylon 6 presents brittle fracture with conglomeration‐like structure, while pure nylon 6 exhibits plastic fracture with island‐like structure. DSC thermograms of nonisothermal crystallization exhibit that the peak of high‐flow nylon 6 broadens compared with pure nylon 6, and the broader peak means the wider processing temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008