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排序方式： 共有140条查询结果，搜索用时 0 毫秒
61.
Sima Shakoorjavan;Monika Dobrzyńska-Mizera;Somaye Akbari;Tomasz Sterzyński; 《Polymer Engineering and Science》2024,64(4):1786-1795
This study details the effect of surface and bulk functionalization of poly(lactic acid) (PLA) with an amine-terminated dendritic polymer, poly(amidoamine) (PAMAM), on the thermal and mechanical properties of PLA-based formulations. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of –NH2 groups derived from PAMAM, through emerging new peaks at around 1650 cm−1 associated with –NH bending vibration and separate double peak between 3705 and 3110 cm−1 associated with stretching vibration of –NH amide groups, in both surface and bulk functionalized PLA samples. Differential scanning calorimetry (DSC) measurements revealed a lowering of cold-crystallization temperature (Tcc) for both surface and bulk functionalized PLA, suggesting that PAMAM served as a nucleating agent. According to thermogravimetric results (TGA), bulk treatment deteriorated the thermal stability of the polymer; while surface modification did not influence the decomposition pathway. Mechanical test results revealed that PAMAM greatly influenced the stiffens and ductility of the composites, with more pronounced changes for higher aminolysis rates. Therefore, the 3-h PAMAM surface functionalization of PLA limits its affinity to solvents' content and enhances crystallization upon permissible deterioration in mechanical properties. 相似文献
62.
The work functions of electrodes can be modified by adding charge transport layers to have good energy level matching with the active materials for organic solar cells (OSCs). Usually, a certain material gives rise to one definite work function of an electrode. In this work it is demonstrated that complexes of poly(amido amine) (generation 3) (PAMAM) with Cu2+ can continuously tune the work function of indium tin oxide (ITO) in a range of 4–5 eV by controlling the ratio of Cu2+ to PAMAM. PAMAM can lower the work function of ITO from 4.60 to 4.07 eV, while Cu2+‐PAMAM can increase the work function. The work function increase depends on the Cu2+‐to‐PAMAM molar ratio, and the work function can be up to 4.96 eV. The Cu2+ effect is ascribed the Cu2+‐caused change in the dipole moment of PAMAM. Moreover, this method can be used to continuously modify the work function of other materials, including Ag, Au, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, and reduced graphene oxide. In addition, PAMAM and Cu2+‐PAMAM are investigated as the charge collection buffer materials of non‐fullerene OSCs of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))]: 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene). The power conversion efficiency can reach 9.2%, which is comparable to that using conventional charge transport materials. 相似文献
63.
In this study, a copper/poly(amidoamine)/multi-walled carbon nanotube/reduced graphene oxide (Cu/PAMAM/MWCNT/rGO) complex was synthesized for fabricating an electrochemical sensor to simultaneously detect nitrate and nitrite ions as inorganic contaminants, and 4-chlorophenol (4-CP) and 1,2,5,8 tetrahydroxy anthraquinone (THA) as organic pollutants. The prepared Cu/PAMAM/MWCNT/rGO electrode was characterized using scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) was performed to investigate the influence of the pH of the solution, concentration of anions, and scan rate on the analytical performance of the electrodes. The simultaneous determination of nitrite/nitrate ions using a Cu/PAMAM/MWCNT/rGO electrode showed sensitivities of 8.030 × 10−3 and 5.370 × 10−3 μA μM−1 mm−2, and limits of detection (LODs) of 0.081 and 0.115 μM, respectively. For the simultaneous determination of 4-CP/THA, the sensitivities of the modified electrode were 0.0105 and 9.399 × 10−3 μA μM−1 mm−2, and detection limits were 0.062 and 0.070 μM respectively. 相似文献
64.
Magdalena Szota Katarzyna Reczy&#x;ska-Kolman Elbieta Pamu&#x;a Olga Michel Julita Kulbacka Barbara Jachimska 《International journal of molecular sciences》2021,22(20)
Two generations of positively charged poly(amidoamine) dendrimers (PAMAMs) were selected for study as potential carriers for the anticancer drug 5-fluorouracil (5FU), a drug primarily used in the treatment of colorectal cancer. Analytical techniques, such as UV-Vis spectrophotometry, NMR Spectroscopy and Laser Doppler Velocimetry (LDV), have shown that the most critical factor determining the formation of a PAMAM–5FU complex is the starting components’ protonation degree. The tests confirmed the system’s ability to attach about 20 5FU molecules per one dendrimer molecule for the G4PAMAM dendrimer and about 25 molecules for the G6PAMAM dendrimer, which gives a system yield of 16% for the fourth generation and 5% for sixth generation dendrimers. Additionally, using the QCM-D method, the adsorption efficiency and the number of drug molecules immobilized in the dendrimer structure were determined. A new aspect in our study was the determination of the change in zeta potential (ζ) induced by the immobilization of 5FU molecules on the dendrimer’s outer shell and the importance of this effect in the direct contact of the carrier with cells. Cytotoxicity tests (resazurin reduction and MTS tests) showed no toxicity of dendrimers against mouse fibroblast cells (L929) and a significant decrease in cell viability in the case of four human malignant cell lines: malignant melanoma (A375), glioblastoma (SNB-19), prostate cancer (Du-145) and colon adenocarcinoma (HT-29) during incubation with PAMAM–5FU complexes. The purpose of our work was to investigate the correlation between the physicochemical properties of the carrier and active substance and the system efficiency and optimizing conditions for the formation of an efficient system based on PAMAM dendrimers as nanocarriers for 5-fluorouracil. An additional aspect was to identify potential application properties of the complexes, as demonstrated by cytotoxicity tests. 相似文献
65.
Dr. Aurora Sganappa Dr. Ezequiel Wexselblatt Dr. Maria Cristina Bellucci Prof. Dr. Jeffrey D. Esko Prof. Dr. Gabriella Tedeschi Prof. Dr. Yitzhak Tor Prof. Dr. Alessandro Volonterio 《Chembiochem : a European journal of chemical biology》2017,18(1):119-125
We present the synthesis of polymeric amino‐ and guanidinoglycosides prepared by tethering neomycin and guanidinoneomycin to PAMAM dendrimers of generations 2 and 4. The ability of these conjugates to promote cellular uptake of high‐molecular‐weight cargo is discussed, together with their cytotoxicity and mechanisms of entry. We demonstrate that the presence of multiple guanidinoneomycin carriers on the PAMAM surface plays an important role in promoting cellular uptake of the dendrimers, maintaining the heparan sulfate specificity and negligible cytotoxicity typical of monomeric guanidinoglycoside molecular transporters. 相似文献
66.
67.
68.
Nano-sized monodisperse gold particles (AuNPs) have received significant attention in the past decade, due to their unique physical properties and good chemical stability, which can lead to a wide variety of potential applications. In this work, TEG-derived PAMAM dendrimers with amine-terminating groups were synthesized and characterized by 1H NMR and FT-IR. These dendrimers were investigated as the templates for preparation of gold nanoparticles through the reduction of HAuCl4 by NaBH4 in water. Stable gold nanoparticles with diameters around 10 nm were obtained in the presence of G2.0 – G5.0 dendrimers and characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The particle size of the produced AuNPs decreased with increasing dendrimer generations. A dendrimer of higher generation has a rigid structure with many end groups on the surface and may play a powerful role in the growth of the AuNPs, as well as having a solid stabilization effect on the AuNPs. 相似文献
69.
以端氢聚二甲基硅氧烷(HTPDMS)和烯丙基缩水甘油醚(AGE)为原料,利用硅氢加成反应合成出单端环氧基聚二甲基硅氧烷(SEPDMS),再将其接枝到一代树枝状聚酰胺-胺(G1 PAMAM)上,制备出聚硅氧烷改性的树枝状-线性聚合物(G1 PAMAM-Si)。通过傅里叶红外光谱(FTIR)、核磁共振氢谱(1HNMR)及纳米粒度分析仪表征分析了产物的结构及乳液性能。将G1 PAMAM-Si应用于皮革加脂工序,并使用扫描电镜(SEM)、X射线衍射谱图分析手段考察了加脂后皮革样品的结构与性能。结果表明,G1 PAMAM-Si加脂后革样胶原纤维间距增大,纤维排列无序度增加。柔软度增加至6.07 mm,抗张强度为17.43 MPa,且撕裂强度增加至94.97 N/mm。 相似文献
70.
聚氧乙烯链封端的聚酰胺-胺树状聚合物的性质与应用 总被引：2，自引：0，他引：2
研究了聚氧乙烯链封端的非离子型聚酰胺-胺树状聚合物的热稳定性以及在造纸助留和催化剂载体上的应用。结果表明,该类树状聚合物具有较好的热稳定性,温度低于300℃无明显热分解行为,最大的热分解温度均为400℃。助留性能测试表明,M4.0G与P44复配双元助留体系(摩尔比1∶23.22),造纸助留率为89.2%,比空白造纸助留率分别提高了18.3%。纸样的物理机械特性:撕裂指数、撕裂强度、耐破指数、耐破强度和抗张指数比空白纸样分别提高了8.6%、1.5%、35.5%、29.6%和4.3%。TEM测试表明:以聚氧乙烯大单体(PEO-A)链封端的聚酰胺-胺树状聚合物样品封装的钯金属纳米粒子单分散性较好,粒径分布在0.75～2.4nm。 相似文献