Ammonium alcohol polyvinyl phosphate intercalated LDHs/epoxy nanocomposites

Journal of Thermal Analysis and Calorimetry - To improve the flame retardancy and mechanical properties of epoxy (EP), a novel intercalated layered double hydroxides (ILDHs) were synthesized by a...     

Non-isothermal crystallization kinetics of exfoliated and intercalated polyethylene/montmorillonite nanocomposites prepared by in situ polymerization

Polyethylene/montmorillonite (PE/MMT) nanocomposites, one intercalated sample with higher MMT content and one exfoliated sample with lower MMT content, were prepared by in situ polymerization using MMT-supported metallocene as catalyst. Non-isothermal crystallization behaviors of these two nanocomposites were investigated and compared. The exfoliated sample exhibits higher crystallization temperature (T_c) than the neat PE, showing nucleation effect of MMT. The intercalated sample has lower T_c than the neat PE due to the confinement of MMT. It is observed that the intercalated sample has longer induction period and faster overall crystallization rate, indicating co-existence of suppression and nucleation effects in this sample. The Avrami plots show that the crystal growth of PE in the intercalated sample is two-dimensional, while it is three-dimensional in the exfoliated sample. The crystallization activation energy of the intercalated sample is slightly smaller than that of the exfoliated sample.     

Zirconium phosphate changing hygroscopicity of polyamide-6 in nanocomposites PA-6/ZrP

Journal of Thermal Analysis and Calorimetry - Hygroscopicity can be understood as ability of any material to absorb water. This investigation aims to study the effect of lamellar zirconium...     

Synthesis and characterization of polymer/clay nanocomposites by intercalated chain transfer agent

In situ synthesis of poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanocomposites by free radical polymerization using intercalated chain transfer agent (I-CTA) in the layers of montmorillonite (MMT) clay is reported. MMT clay was ion-exchanged with diethyl octyl ammonium ethylmercaptan bromide, which acts both as suitable intercalant and as chain transfer agent. These modified clays were then dispersed in methyl methacrylate (MMA) or styrene (St) monomers in different loading degrees to carry out the in situ free radical polymerization. The intercalation ability of the chain transfer agent and exfoliated nanocomposite structure were evidenced by both X-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied.     

Adsorption behaviors of poly(amido amine) dendrimers with an azacrown core and long alkyl chain spacers on solid substrates

Adsorption behaviors of functional poly(amido amine) dendrimers with an azacrown core and long alkyl chain spacers were investigated on gold and self-assembled monolayer (SAM) by means of time course attenuated total reflection-surface enhanced infrared absorption and surface plasmon resonance spectroscopies. While 1.5th and 2.5th generation (G1.5 and G2.5) ester-terminated dendrimers were slightly adsorbed on all substrates examined, the adsorption of G2 amine-terminated dendrimer increased in the order dodecanethiol SAM相似文献   

无定形（磷酸氢－二苯基次膦酸）锆－氯化铁复合物催化烷基化反应

制得无定形（磷酸氢－二苯基次膦酸）锆－氯化铁复合物Ｚｒ（ＨＰＯ＿４）＿（１．５）［Ｏ＿２Ｐ（Ｃ＿６Ｈ＿５）＿２］·［ＦｅＣｌ＿２（ＯＨ）］．该复合物不易吸潮，不冒烟，在空气中稳定，对卤代烷与芳香烃在液相的烷基化反应有较好的催化活性；反应条件温和，产物收率高，操作方便，后处理简单，并可多次重复使用。     

无定形（磷酸氢—二苯基次膦酸）锆—氯化铁复合物催化烷基化反应

制得无定形（磷酸氢－二苯基次膦酸）锆－氯化铁复合物Ｚｒ（ＨＰＯ４）１．５（Ｏ２Ｐ（Ｃ６Ｈ５）２）．（ＦｅＣｌ２（ＯＨ）。该复合不易吸潮，不冒烟，在空气中稳定，对代烷与芳得在液相的烷基化应有较好的催化活性，反应条件温和，产物收率高，操作方便，后处理简单，并可多次重复使用。     

Synthesis of organically templated nanoporous Tin(II/IV) phosphate for radionuclide and metal sequestration

Nanoporous tin(II/IV) phosphate materials, with spherical morphology, have been synthesized using cetyltrimethylammonium chloride [CH3(CH2)15N(CH3)3Cl] as the surfactant. The structure of the material is stable at 500 degrees C; however, partial oxidation of the material occurs with redox conversion of Sn2+ to Sn4+, resulting in a mixed Sn(II)/Sn(IV) material. Preliminary batch contact studies were conducted to assess the effectiveness of nanoporous tin phosphate, NP-SnPO, in sequestering redox-sensitive metals and radionuclides, technetium(VII), neptunium(V), thorium(IV), and a toxic metal, chromium(VI), from aqueous matrixes. Results indicate that tin(II) phosphate removed >95% of all contaminants investigated from solution.     

Viscoelastic solution of long polyoxyethylene chain phytosterol/monoglyceride/water systems

We have studied the rheology and structure of a mixed long polyoxyethylene chain phytosterol (PhyEO₃₀) and monoglyceride (monolaurin (ML) or monopalmitin (MP)) surfactants in an aqueous system. Both ML and MP are insoluble in 10 wt.% PhyEO₃₀ solution at normal room temperature, but their solubility is found to increase with the rise of temperature and an isotropic solution is formed at higher temperature. A maximum viscosity as a function of temperature appears as ML or MP is solubilized in the micellar solution of PhyEO₃₀. With increasing temperature, viscosity increases rapidly for higher monoglyceride content and forms viscoelastic solution. The oscillatory rheological behavior of the viscoelastic solution can be described by Maxwell model at low-frequency region, which is the typical pattern of entangled wormlike micelles. Upon successive increase in temperature, the viscosity decreases and ultimately a phase separation occurs. Small-angle X-ray scattering measurements were performed to provide a supportive structural evidence for the rheological data.     

Azobenzene derivatives with a long alkyl chain and aminoxyls

A trans-azobenzene derivative with a long alkyl chain and a TEMPO radical showed photo-induced isomerization to become the corresponding cis-isomer with a significant change of its intermolecular magnetic interaction from a weak ferromagnetic one based on the CW model to a relatively strong antiferromagnetic one based on the ST model with the J-value of 36.7 K.     

Extraction with long chain amines-VII polarographic determination of uranium

A polarographic determination of uranium is described, based on the highly selective extraction of uranium(VI) with a chloroform solution of trioctylammonium chloride, followed by re-extraction of uranium into an aqueous 0·5M KCl-0·5M HCl solution, which also serves as the polarographic supporting electrolyte. In this medium, uranium(VI) is reduced at the dropping mercury electrode to give two polarographic waves, the first of which is of analytical significance. In this way it is possible to determine 50–2400 μg of uranium in 1 ml of supporting electrolyte and in the presence of large amounts of accompanying elements.     

Film structures of poly(amido amine) dendrimers with an azacrown core and long alkyl chain spacers on water or Ag nanoparticle suspension

Newly designed poly(amido amine) dendrimers, which have an azacrown core, hexyl spacers, and methyl ester terminals (aza-C6-PAMAM dendrimer), were spread at the air-water and air-silver nanoparticle suspension interfaces, and their film structures were examined by surface pressure-area (pi-A) and surface potential-area (DeltaV-A) isotherms and epifluorescence microscopy. It was revealed that generation (G) 1.5 aza-C6-PAMAM dendrimer on a water subphase formed homogeneous film with face-on configuration, and this configuration was maintained during compression. On the other hand, a G2.5 dendrimer film on the air-water interface took initially homogeneous and face-on configuration that was followed by the conformational change during compression. Using a silver nanoparticle suspension as subphase, G1.5 film was significantly reinforced, and the partial collapse (cracks) in the film appeared as network texture. For a G2.5 dendrimer film, the pi-A and DeltaV-A isotherm properties were similar to that on the water subphase except for the collapsed film; small spots instead of cracks were formed under the film after collapse. These effects of the silver nanoparticle may be due to the formation of a dendrimer/silver nanoparticle composite. The formation process of the nanocomposite film was verified by UV-vis spectroscopy. For the G1.5 dendrimer, silver clusters and nanoparticles adsorbed to the dendrimer film after spreading and formed a small amount of aggregates. During compression, the aggregation proceeded even at low surface pressure. For the G2.5 dendrimer, a dendrimer/nanoparticle composite was also formed after spreading. However, with the initial compression, the absorption bands of clusters, nanoparticles, and aggregate increased together. Upon further compression, while the bands of cluster and nanoparticles decreased, the bands of aggregate still increased. These results suggest that the G2.5 dendrimer covered the cluster and nanoparticles more efficiently than the G1.5 dendrimer did because of the larger molecular size.     

Structure/performance relationships in long chain dimethylamine oxide/sodium dodecylsulfate surfactant mixtures

Dramatic differences in the structure of mixed micelles of long chain amine oxides and sodium dodecylsulfate are noted as a function of composition. In the L₁ micellar pseudophase, a sphere-to-rod transition driven by ion-dipole interactions between the dissimilar headgroups leads to synergisms in aqueous solution thickening, Ross-Miles foaming, and nonpolar oil solubilization. For example, an astounding seven orders of magnitude increase in the zero shear viscosity and viscoelastic properties are observed at a single total surfactant concentration. The sphere-to-rod transition can be viewed in FT-IR by examining both the CH₂ stretching for the methylene tails, and the S-O stretching modes for the sulfate headgroups.     

A new quantitative radiochemical separation procedure to determine Ir at 10−12 g/g level in geological samples by a long chain primary amine extraction

A radiochemical separation procedure has been set up to determine Ir of 10^?12 g/g level and other noble metals in geological samples by using a long chain s-alkyl primary amine, N-1923, as an extractant. A series of factors affecting the chemical recovery of Ir were considered, including extractant, diluent, oxidant, oxidation temperature an time, extraction acidity, reflux acidity and time, etc. Some improvements in the procedure for geological samples were made, i.e. eliminating interference from chromium and raising recoveries of noble metals in geological samples. The extraction percentages of noble metals are more than 95% in one step of extraction and of base metals are generally less than 0.5%.     

Interaction between phospholipid vesicular structures with long chain zwitterionic surfactants

Solubilization of different zwitterionic phospholipid vesicles structures such as L--phosphatidylcholine (PC) and 1,2-didecanoyl-sn-glycero-3-phosphocholine (DPC) have been studied in aqueous bulk by using zwitterionic surfactant dimethylhexadecylammoniopropanesulfonate (HPS). This has been done by studying the aggregation of HPS in pure water and in the presence of 7–36 M of fixed concentrations of each lipid with the help of pyrene fluorescence intensity (I ₁/I ₃) measurements. The fluorescence measurements showed that HPS monomers undergo two kinds of aggregation process, which were identified by the three breaks in a plot of pyrene fluorescence versus HPS concentration. The first two breaks, C ₁ and C ₂, indicate the onset and completion of vesicle solubilization respectively, upon incorporation of HPS monomers into the vesicles and led to solubilization in the form of mixed micelles. This process was not clearly visible at low lipid concentration. We evaluated the partition coefficient (K), which defines the degree of partitioning of surfactant monomers into the vesicles with respect to the aqueous medium. A high K value of HPS-lipid aggregates indicates the stronger interactions between surfactant and lipid vesicles. The K values evaluated for PC and DPC are quite close to each other, which indicates that K values were independent of phospholipid chain length.     

Interaction of long chain alkylammonium cations with reduced charge montmorillonite

Reduced charge montmorillonites (RCM) were prepared using lithium thermal treatment. The sorption of octylammonium (OA), dodecylammonium (DDA) and hexadecylammonium ions (HDA) on differently charged samples were studied. The amounts of DDA and HDA sorbed on each RCM exceed the cation exchange capacity (CEC) but that of OA exceeds only the CEC of samples with the lowest CEC. The sorption is affected not only by the layer charge but also by the formation of collapsed interlayer spaces in the lowest charged montmorillonites. X-ray measurements confirmed the decrease of the layer charge after lithium thermal treatment and the layer charge heterogeneity in RCMs.     

Studies on the thermal properties of caprolactam/long chain lactam copolymer

The thermal properties of caprolactam/long chain lactam copolymer were studied with a Perkin-Elmer DSC 7. The melting point (T _m), heat of fusion (δH _m), crystalline degree (X _c), crystallization temperature (T _c) and glass transition temperature (T _g) of the copolymers increase with decrease of the content of the log chain lactam. From the changes in the mechanical properties with corresponding changes in the thermal properties, it is clear that the copolymers are thermal plastic and elastic. In addition, it is found that the results at a heating rate of 10 deg·min^?1 are almost the same as that at 20 deg·min^?1 after thermal history is erased.     

Zirconium phosphate/phosphonate multilayered films based on push-pull stilbazolium salt: synthesis, characterization and second harmonic generation

The preparation of materials featuring enhanced second harmonic generation (SHG) values by self-assembly of molecules characterized by high second-order non-linear optic (NLO) activity is nowadays an important and challenging field of research. In order to show SHG the material must have an acentric structure with the dipoles of the molecular components oriented in the same direction and this is synthetically fairly difficult to achieve. This study describes the synthesis of the push-pull stilbazolium salt and its assembly in multilayered acentric thin films, on quartz glass surface, by using the zirconium phosphate/phosphonate (Zr-PO(x)) technique. A particular care has been paid to the optimization of the surface preparation and of the deposition conditions. This allows to obtain highly homogeneous lamellar inorganic-organic materials showing satisfactory second harmonic generation (SHG) values together with high chemical, thermal and mechanical stabilities which are necessary for their integration in optoelectronic devices.     

Thermal properties of ethylene/long chain α-olefin copolymers produced by metallocenes

Metallocene type copolymers of ethylene with the α-olefins 1-octene, 1-tetradecene and 1-octadecene were characterized by dynamic scanning calorimeter (DSC) and by dynamic mechanical analysis (DMA). At a similar comonomer content above 3 mol%, the higher α-olefins gave lower melting points, crystallinities and densities than 1-octene. In DSC a separation technique sorting the crystalline sequence lengths of the polymer into groups was applied, and DSC index, DI, which gave a semiquantitative idea of the chemical homogeneity of the comonomer compositional distributions. By DMA the storage modulus as an indicator of stiffness and loss modulus and loss tangent as a measure of the effect of branching on the β relaxations were studied. The DMA measurements showed the loss modulus maximum to be a more sensitive value than the loss tangent maximum for the characterization of the comonomer distribution. The intensity of the β transition of 1-octadecene did not increase with increasing branching in contrast to the situation for 1-octene and 1-tetradecene copolymers.     

Synthesis of aliphatic diamine and polyetherimide with long perfluoroalkyl side chain

The monomer, 2-(perfluorohexylmethyl)butan-1,4-diamine (TFD), was prepared from itaconic acid dimethyl ester via the addition of perfluorohexyl iodide followed by the gradual transformation of ester groups into amino groups. The polymerization of bisphenol-A diphthalic anhydride (BAPA) with TFD led to hydrophobic fluorinated polyetherimide (FPEI) with R_F=C₆F₁₃ side chain. This polymer makes it possible to cast films.