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     

金属配位树枝状大分子鞣剂的合成及表征

以乙二胺和丙烯酸甲酯为原料合成了 0 .5～ 3 .5代的树状聚酰胺大分子 ,在碱性条件下水解 ,将其外围官能团转变为羧基 ,并与CrCl3 配位得到金属配位树状大分子鞣剂。利用红外光谱、核磁共振、紫外光谱等手段对合成产物进行了表征。     

改性天然橡胶MG-30和树枝状聚酰胺-胺对轮胎胎面胶耐磨性能的影响

研究甲基丙烯酸甲酯接枝改性的天然橡胶（NR）MG-30和树枝状聚酰胺-胺（PAMAM）对全钢子午线轮胎胎面胶耐磨性能的影响。结果表明：与生产配方胶料相比,加入MG-30后的NR胶料的门尼特性和硫化特性均无明显变化、物理性能有所提高,但邵尔A型硬度增大;加入PAMAM后,NR/MG-30并用胶的物理性能和耐磨性能明显提高,邵尔A型硬度减小。     

Modular Integration of Upconverting Nanocrystal–Dendrimer Composites for Folate Receptor‐Specific NIR Imaging and Light‐Triggered Drug Release

Upconversion nanocrystals (UCNs) display near‐infrared (NIR)‐responsive photoluminescent properties for NIR imaging and drug delivery. The development of effective strategies for UCN integration with other complementary nanostructures for targeting and drug conjugation is highly desirable. This study reports on a core/shell‐based theranostic system designed by UCN integration with a folate (FA)‐conjugated dendrimer for tumor targeting and with photocaged doxorubicin as a cytotoxic agent. Two types of UCNs (NaYF₄:Yb/Er (or Yb/Tm); diameter = ≈50 to 54 nm) are described, each displaying distinct emission properties upon NIR (980 nm) excitation. The UCNs are surface modified through covalent attachment of photocaged doxorubicin (ONB‐Dox) and a multivalent FA‐conjugated polyamidoamine (PAMAM) dendrimer G5(FA)₆ to prepare UCN@(ONB‐Dox)(G5FA). Surface plasmon resonance experiments performed with G5(FA)₆ dendrimer alone show nanomolar binding avidity (K_D = 5.9 × 10⁻⁹m ) to the folate binding protein. This dendrimer binding corresponds with selective binding and uptake of UCN@(ONB‐Dox)(G5FA) by FAR‐positive KB carcinoma cells in vitro. Furthermore, UCN@(ONB‐Dox)(G5FA) treatment of FAR(+) KB cells inhibits cell growth in a light dependent manner. These results validate the utility of modularly integrated UCN‐dendrimer nanocomposites for cell type specific NIR imaging and light‐controlled drug release, thus serving as a new theranostic system.     

Grafting and phosphonic acid functionalization of hyperbranched polyamidoamine polymer onto ultrafine silica

In this study, grafting of hyperbranched polyamidoamine (PAMAM) polymer onto ultrafine silica followed by functionalization via the introduction of phosphonic acid groups into the branch ends was performed. First, an initiating site was incorporated into the silica surface by reacting the silica silanol group with 3‐aminopropyltriethoxysilane, producing amino‐functionalized silica. The free amine group content was altered by varying the ratio of methanol to water in the hydrolysis step of the silanization reaction. Grafting of PAMAM was attained by three rounds of sequential Michael addition of silica amino groups to methyl acrylate and amidation of the resulting terminal methyl ester groups with ethylenediamine. Completion of the grafting reaction in each step was clearly confirmed using FTIR analysis. Excessive ethylenediamine and unattached hyperbranched PAMAM present in the reaction product were removed by dialysis with a molecular weight cutoff of 6000–7000 Daltons. However, the amino group content determined in each step was found to be significantly lower than theoretically expected, perhaps indicative of side reactions and, in later stages, steric hindrance. The resultant hyperbranched PAMAM‐grafted onto silica was functionalized by phosphorylation of the terminal amino groups by a Mannich type reaction, producing the phosphorylated hyperbranched PAMAM‐grafted silica. Then its application on cotton fabric to produce fire‐retardant cellulose was tentatively investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Composites membranes based on Nafion and PAMAM dendrimers for PEMFC applications

The aim of this work consists in to incorporate organic compounds as PAMAM (Poly-amidoamine) dendrimers into the polymeric Nafion matrix to prepare composite membranes as a possible alternative to reduce methanol crossover effect. Composite Nafion membranes were prepared using a 3 wt% of Generation-4 hydroxyl-terminated PAMAM (G4OH) dendrimers containing 64-terminal OH-functional groups. The influence of PAMAM-(G4OH) dendrimer on chemical–physical properties of the composite membrane was highlighted resulting in a reduction of the methanol permeability (1.05 × 10⁻⁶ cm² s⁻¹) if compared to a recast bare Nafion membrane (8.19 × 10−6 cm² s⁻¹), used as a reference. Good proton conductivity was also observed for PAMAM-(G4OH) composite membrane. The polarization curves carried out at 100 °C in the presence of 2 M methanol have revealed the higher performance of the PAMAM-(G4OH) membrane when compared to a recast Nafion membrane.     

微波法制备3．5GPAMAM树状大分子保护的金纳米粒子

以3．5GPAMAM（3．5代聚酰胺一胺型）树状大分子为保护剂，利用微波法还原HAuCl4溶液制备金纳米粒子．考察了当3．5GPAMAM与HAuCl4物质的量的比一定时，微波照射不同时间对金纳米粒子大小及形状的影响；以及同一照射条件下，3．5GPAMAM与HAuCl4不同的物质的量比值对金纳米粒子大小及形状的影响．利用紫外可见分光光度计、透射电子显微镜对其进行了表征．结果表明，当3．5GPAMAM与HauCl4物质的量的比值一定时，金纳米粒子的形状和大小受微波照射时间长短的影响不大；适当延长照射时间，制得的金纳米粒子的分散性较好．在相同照射条件下，随着3．5GPAMAM与HAu—C14物质的量比值的减小，得到的金纳米粒子粒径逐渐变大，且分散性变差．     

Electrochemistry of polyamidoamine dendrimers ester gel electrolytes

This paper described the first example of polyamidoamine dendrimers ester (PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as a plasticizer. The polymer films are solid and sticky. Background cyclic voltammetry (CV) shows a potential window between 0.7 and -0.7 V vs. Ag/AgCl. The voltammetry of ferrocene and 7,7,8,8-tetracyanoquinodimethane (TCNQ) indicates that diffusion coefficients are in the range of 10^-8-10^-9 cm^2/s.Ionic conductivities are approximately 10^-6 S/cm. Similar films using dimethyl sulfoxide (DMSO) as a plasticizer instead of MPEG-400 have demonstrated ionic conductivities of 10-4 S/cm and reversible voltammetry. However, UV spectropho-tometry shows that 70% of the DMSO is lost under vacuum, indicating the difficulty in quantifying the DMSO content when exposed to vacuum.     

Thin Metal Films Deposited on Dendrimer Monolayers

Chemical interactions and the evolution of surface morphology resulting from deposition of Cr and Co onto dendrimer monolayers have been investigated by XPS, RAIRS, and AFM. Evidence is presented for formation of metal nitrides and mediation of film morphology as a function of the metal and generation number of the dendrimer comprising the monolayer.     

硅胶表面上聚酰胺-胺的合成及其对Ag（Ⅰ）的吸附

用硅烷偶联剂对硅胶表面进行氨基功能化,利用氨基与丙烯酸甲酯发生的Michael加成反应和乙二胺与酯进行的交换反应,在硅胶表面合成了聚酰胺-胺（PAMAM-SG）树状大分子,用红外光谱对PAMAM-SG的结构进行了表征。研究了溶液pH、浓度和吸附温度对PAMAM-SG吸附Ag（Ⅰ）的影响。结果表明,溶液的最佳吸附pH值范围为4.0~7.0,吸附速率随时间的增加逐渐降低,随温度的升高有一定升高,在30℃时具有较好的吸附性能,吸附量达59.9 mg/g;各代PAMAM-SG的吸附量大小依次为2.0G〉1.5G〉1.0G〉0.5G〉0G〉-0.5G;吸附容量随浓度的增大而增加,直至平衡。