Efficient Preparation of Hybrid Linear‐Branched Esters of PEG‐PEE Derivatives

A simple and efficient preparation of a number of hybrid linear‐branched PEG esters are described. The polymers are generated by direct coupling of PEG–carboxylic acids and a variety of pentaerythritol ethoxylates using carbon tetrabromide catalyst.     

Polyethylene Glycol–Enhanced Chemoselective Synthesis of Organic Carbamates from Amines,CO2, and Alkyl Halides

An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO₂, and alkyl halides underwent a three-component reaction with the aid of K₂CO₃ and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate.

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Thermal and thermo-oxidative degradation of high density polyethylene/fullerene composites

Fullerene (C₆₀)/high density polyethylene (HDPE) composites were studied in order to understand for their behaviors on thermal and thermo-oxidative degradation. Under different atmosphere, the influences of C₆₀ on the thermal stability of HDPE are different. Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) demonstrate that in N₂ the addition of C₆₀ increases the onset decomposition temperature by about 10 °C with more heavy compounds (more than 34 carbon). Also the thermal stability of HDPE in air is remarkably improved with the addition of C₆₀. When the content of C₆₀ is 2.5 wt% the onset decomposition temperature increases by about 91 °C. The results of viscoelastic behavior and gel content reveal that C₆₀ can trap the alkyl radicals and alkyl peroxide radicals to inhibit hydrogen abstraction to suppress the chain scission and preserve the long chain structure. However, in the absence of C₆₀ or with low C₆₀ concentration, hydrogen abstraction occurs, resulting in the formation of a series of alkyl radicals and alkyl peroxide radicals, which accelerates the chain scission and plays a leading role in the thermal oxidative degradation.     

Synthesis of Some Additives and Study Effect of Gas Oil Composition on Flow Properties

Nine additives were prepared by esterification of dibasic acid (succinic, adipic, sebacic acid) and polyethylene glycol (Mol.wt.=600, 1000, 4000). These additives were characterized by infrared spectral analysis, average molecular weight and polydispersity index. Their influence on the depression of pour point for two type of paraffin gas oils (G1 and G2) were investigated, blends of paraffin gas oils G1 and G2 by different ratio, when their untreated and treated by additives were evaluated as pour point depressant in comparison with the original paraffin gas oils G1 and G2.

The effect of additive type and gas oil composition on wax crystal modification were studied using the photo micrographic analysis. Diethoxylate (eo=182) sebacate with blend gas oil No. 3 has achieved the best performance as pour point depressant. The photo micrographic analysis showed that, the wax morphology was greatly modified to fine dispersed crystals of compact size. A correlation between the pour point depression and the extent of wax modification was detected.     

Application of New Modified Poly(ethylene Oxide)-Block-Poly(propylene oxide)-Block-Poly(ethylene oxide) Copolymers as Demulsifier for Petroleum Crude Oil Emulsion

Water soluble nonionic amphiphilic block copolymers based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(propylene glycol) (PPG) were prepared. Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymers, PEG-PPG-PEG, were prepared in the normal condition. The chemical composition and molecular weights of the prepared copolymers were determined from ¹H NMR and GPC techniques. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The prepared nonionic surfactants were evaluated as demulsifiers for water in crude-oil emulsions that were pronounced at different ratios of crude oil: water at 318 K and 333 K. The experimental results showed that the dehydration rate of the prepared demulsifiers reached 100% based on demulsifier chemical compositions and concentrations.     

Ferroelectric liquid crystal composites based on the porous stretched polyethylene films

Electro-optically active polymer–liquid crystal composites based on ferroelectric liquid crystals and stretched porous polyethylene films were developed. The alignment of ferroelectric liquid crystals incorporated into the porous polyethylene films with average porous diameter of around 200 nm was observed and studied. It was shown experimentally that these samples containing ferroelectric liquid crystals are flexible electro-optical films exhibiting a saturation electric field near 2·10⁷ Vm^?1 and a response time of about 30 μs under the action of the saturation field. A simple theoretical model of ferroelectric liquid crystal molecules' complete reorientation in electric fields inside pores of the films has been proposed and confirmed experimentally.     

PEG接枝氧化石墨烯的制备与细胞成像

通过酯化反应将不同分子量的聚乙二醇（PEG）接枝到氧化石墨烯（GO）表面,得到系列GO-PEG。利用傅里叶变换红外光谱（FTIR）、拉曼光谱（Raman）、扫描电子显微镜（SEM）对GO-PEG的结构和形貌进行了表征,用热重分析（TGA）测定了GO-PEG中PEG的接枝量。SEM结果表明GO-PEG的剥离程度高于GO。GO-PEG在磷酸盐缓冲溶液中具有良好的分散稳定性,稳定性与接枝量呈正相关。GO-PEG通过非共价键合作用对荧光素（Flu）的负载量可达1.75mg·mg^-1,且负载量受接枝量影响;另外,GO-PEG对Flu的释放行为具有pH值触发药物释放性能。将接枝PEG的端羟基与Flu共价键合,所得GO-PEG₆₀₀₀-Flu荧光探针实现了对HepG₂细胞的成像。     

Polyaspartamide–Polylactide Graft Copolymers with Tunable Properties for the Realization of Fluorescent Nanoparticles for Imaging

Here, the synthesis and the characterization of novel amphiphilic graft copolymers with tunable properties, useful in obtaining polymeric fluorescent nanoparticles for application in imaging, are described. These copolymers are obtained by chemical conjugation of rhodamine B (RhB) moieties, polylactic acid (PLA), and O‐(2‐aminoethyl)‐O′‐methyl poly(ethylene glycol) (PEG) on α,β‐poly(N‐2‐hydroxyethyl)‐d,l ‐aspartamide (PHEA). In particular, PHEA is first functionalized with RhB to obtain PHEA–RhB with a derivatization degree in RhB (DD_RhB) equal to 0.55 mol%. By varying the reaction conditions, different amounts of PLA are grafted on PHEA–RhB to obtain PHEA‐RhB‐PLA with DD_PLA equal to 1.9, 4.0, and 6.2 mol%. Then, PEG chains are grafted on PHEA‐RhB‐PLA derivatives to obtain PHEA‐RhB‐PLA‐PEG graft copolymers. The preparation of polymeric fluorescent nanoparticles with tunable properties and spherical shape is described by using PHEA‐RhB‐PLA‐PEG with DD in PLA and PEG equal to 4.0 and 4.9 mol%, by following easily scaling up processes, such as emulsion‐solvent evaporation and high pressure homogenization (HPH)‐solvent evaporation techniques.