Surface modification of CaCO3 filler and its characterization using inverse gas chromatography (IGC)

A CaCO₃ filler was treated by generally used coupling agents and a special one — ethylene-octene copolymer (POE)-g-maleic anhydride (MAH). Fourier transform infrared spectroscopy (FTIR) results show that the special coupling agent POE-g-MAH, in a chemical reaction with CaCO₃, can produce an interfacial layer stronger than simple physical adhesion attained with usual coupling agents. Inverse gas chromatography (IGC) was used to investigate the surface free energy of CaCO₃ after surface modification and to optimize the monolayer content of coupling agents. Based on the IGC results, it can be deduced that the monolayer cover is around 1.9% for CaCO₃ treated with a titanate coupling agent. Scanning electron microscope (SEM) observation results show that the separated morphology existed in the ternary composites containing CaCO₃ after surface treatment with coupling agents, whereas the core-shell morphology was obtained in the ternary composites with POE-g-MAH. The encapsulation of the CaCO₃ filler treated with POE-g-MAH was caused by the strong chemical reaction between the elastomer and CaCO₃ particles. __________ Translated from Journal of Northwestern Polytechnical University, 2007, 25(2): 274–278 [译自: 西北工业大学学报]     

Cobalt(II) ion-selective electrode with solid contact

A new all plastic sensor for Co²⁺ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10⁻⁶ mol L⁻¹ and almost theoretical Nernstian slope in the activity range 4.0 × 10⁻⁶–1 × 10⁻¹ mol L⁻¹ of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co²⁺ in real samples and as an indicator electrode in potentiometric titration of Co²⁺ ions with EDTA.      

Total-reflection X-ray fluorescence: An alternative tool for the analysis of magnetic ferrofluids

This work presents the first application of the total-reflection X-ray fluorescence (TXRF) to the compositional study of magnetic ferrofluids. With the aims of validating the best analytical conditions and also, limitations of the TXRF in the compositional study of these materials, an alternative empirical method, based in the use of angle-dependence TXRF (AD-TXRF) measurements, is proposed. Three kinds of ferromagnetic nanoparticles, with different morphologies, have been studied. The techniques of inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) have been used to validate the TXRF results. In contrast with the plasma techniques, the developed TXRF procedure need not of previous chemical acid digestion. Additionally, two procedures of magnetic nanoparticles synthesis, co-precipitation and laser-pyrolysis, have been checked for the contaminants trace metals Zn, Mn and Cr. It has been found that the method of laser-pyrolysis produces nanoparticles of higher purity.     

Synthesis of phosphinodiselenoic acid esters and their application as RAFT agents in styrene polymerization

Phosphinodiselenoic acid esters are synthesized from the reaction of chlorodiphenylphosphine and aryl- or alkyl-magnesium bromide in the presence of selenium powder. They are employed as RAFT agents in thermally initiated, styrene polymerization. The phosphinodiselenoic acid esters 6a and 6b showed some degree of control over the radical polymerization of styrene.     

Thermal decomposition of various alkyl onium organoclays: Effect on polyethylene terephthalate nanocomposites' properties

The thermal stability of organically modified layered silicates is determinant for processing polymer nanocomposites and is believed to play a key role on their properties. In this work, alkyl phosphonium, alkyl pyridinium and dialkyl imidazolium surfactants were used as intercalating agents for the preparation of highly thermally stable organophilic montmorillonites. The thermal decomposition of the surfactants and of their organoclays was studied by combined thermogravimetric analysis (TGA) and mass spectroscopy (MS), which allowed the identification of specific volatile compounds issued from the degradation. In order to investigate the influence of the thermal decomposition of the intercalating agent during processing, the various organoclays were incorporated in a polyethylene terephthalate (PET) matrix. The color of the nanocomposites was significantly affected by the thermal decomposition of the intercalating agent. In the case of the alkyl pyridinium modified clay, the degradation of the intercalating agent during processing was found to alter the clay dispersion. Finally, the crystallization was analyzed by differential scanning calorimetric (DSC) analysis and polarized optical microscopy (POM): it was demonstrated that the kinetics of nucleation and growth is not only affected by the dispersion state of the clay, but also depends on the clay/polymer interface properties, and therefore on the nature of the intercalating agent.     

奈必洛尔的不对称合成

首先合成4-氟-2-(5-羟基戊烷基-3-烯)-苯酚(2), 再经Sharpless不对称环氧化等反应分别得到2-氨基-1-[6-氟- (2S)-3,4-二氢-2H-2-苯并吡喃]-(1R)-1-乙醇(6)和6-氟-2-[(2R)-2-环氧乙烷基]-(2R)-3,4-二氢苯并吡喃(10). 最后, 6和10发生亲核开环反应即得到目标产物奈比洛尔. 整个合成路线简单易行, 并在原有文献的基础上有较大改进, 使收率大大提高, 总收率由文献的2.1%提高到14.1%.     

Understanding the folding process of synthetic polymers by small-molecule folding agents

Two acceptor containing polyimides PDI and NDI carrying pyromellitic diimide units and 1,4,5,8-naphthalene tetracarboxy diimide units, respectively, along with hexa(oxyethylene) (EO6) segments as linkers, were prepared from the corresponding dianhydrides and diamines. These polyimides were made to fold by interaction with specifically designed folding agents containing a dialkoxynaphtha-lene (DAN) donor linked to a carboxylic acid group. The alkali-metal counter-ion of the donor carboxylic acid upon complexation with the EO6 segment brings the DAN unit in the right location to induce a charge-transfer complex formation with acceptor units in the polymer backbone. This two-point interaction between the folding agent and the polymer backbone leads to a folding of the polymer chain, which was readily monitored by NMR titrations. The effect of various parameters, such as structures of the folding agent and polymer, and the solvent composition, on the folding propensities of the polymer was studied.     

A carbohydrate-linked hypericinic photosensitizing agent

With respect to an enhanced solubility under physiological conditions, a carbohydrate-containing hypericin-based second-generation photosensitizer was prepared. Its photochemical properties were tested by means of the light-sensitized destruction of bilirubin IXα to be even better than those of the parent compound hypericin. Investigations on binding-interactions with DNA showed promising results as well.     

Polymer toughening using residue of recycled windshields: PVB film as impact modifier

In this work, poly(vinyl butyral) (PVB) film originated from the mechanical separation of windshields was tested as an impact modifier of Polyamide-6 (PA-6). The changes undergone by PVB film during the recycling process and the blend manufacturing were evaluated by thermal analyses, infrared spectroscopy and loss on ignition. Blends of PA-6/original PVB film and PA-6/recovered PVB film were obtained in concentrations ranging from 90/10 to 60/40. The mechanical properties of the blends were investigated and explained in light of the blends morphologies, which in turns were correlated to the changes undergone by the PVB film during the recycling process. The original film presented a plasticizer content of 33 wt.%, which decreased to as low as 20 wt.% after the recycling and blend preparation processes. The PA-6/PVB film blends presented lower values of tensile strength and Young’s modulus than Polyamide-6, but all blends presented a dramatic increase in their toughness, with a special feature for the 40 wt.% blend, which resulted in a super toughened material (impact strength exceeding 500 J/m). Similar results were obtained with recovered PVB film and super tough blends were also obtained. The use of recovered PVB resulted in a smaller improvement of the impact strength due to the loss of plasticizer undergone during the recycling process. The morphological observations showed that if the interparticle distance is smaller than around 0.2 μm (critical value), the notched Izod impact strength values increase considerably and the fracture surface of blends exhibit characteristics of tough failure.     

Polymer coated sensor array based on quartz crystal microbalance for chemical agent analysis

Quartz crystal microbalance (QCM) gas sensors based on polymeric material were fabricated and their gas response characteristics were examined for four simulant gases of chemical agents, which were dimethyl methyl phosphonate (DMMP), N,N-dimethylacetamide (DMA), 1,5-dichloropentane (DCP) and dichloroethane (DCE). For the selection of appropriate coating materials, both principal component analysis (PCA) and hierarchical cluster methods were applied to a data set collected from 15 QCM sensors for 12 analytes. Four appropriate coating materials were selected after optimizing the correlation between the 15 coating materials and the first four principal component (PC) factors. The four chosen polymers were used as sensitive component for a sensor array, and then PCA is adapted to classify four simulant gases. The results show that the QCM sensor array has high sensitivity and selectivity to four chemical agents.