Ring-opening Copolymerization of ε-Caprolactone and δ-Valerolactone Catalyzed by a 2,6-Bis(amino)phenol Zinc Complex

In combination with methyllithium,a 2,6-bis(amino)phenol zinc complex 1 was used in the ring-opening polymerization ofδ-valerolactone in the absence or presence of benzyl alcohol and showed high efficiency,mainly producing cyclic and linear polyvalerolactones,respectively.On the basis of homopolymerization,the ring-opening copolymerization ofε-caprolactone andδ-valerolactone was investigated.The P(CL-co-VL)random copolymers,PCL-b-PVL and PVL-b-PCL diblock copolymers,were prepared by varying the feeding strategy(premixing or sequential feeding).The copolymer composition was adjusted by varying the feeding ratio of two monomers.The structure and thermal properties of obtained polymers were characterized by GPC,1 H-NMR,13 C-NMR,MALDI-TOF mass spectroscopy,and DSC,respectively.     

Morphology, crystallization and mechanical properties of poly(ɛ-caprolactone)/graphene oxide nanocomposites

A series of nanocomposites based on poly(ε-caprolactone) (PCL) and graphene oxide (GO) were prepared by in situ polymerization. Scanning electron microscopy observation revealed not only a well dispersion of GO but also a strong interfacial interaction between GO and the PCL matrix, as evidenced by the presence of some GO nanosheets embedded in the matrix. Effects of GO nanofillers on the crystal structure, crystallization behavior and spherulitic morphology of the PCL matrix were investigated in detail. The results showed that the crystallization temperature of PCL enhanced significantly due to the presence of GO in the nanocomposites, however, the addition of GO did not affect the crystal structure greatly. Thermal stability of PCL remarkably increased with the addition of GO nanosheets, compared with that of pure PCL. Incorporation of GO greatly improved the tensile strength and Young’s modulus of PCL without a significant loss of the elongation at break.     

Studies of the enthalpy relaxation and the “multiple melting” behavior of semicrystalline poly(arylene ether ether ketone) (PEEk)

We report the results of an investigation by differential scanning calorimetry (DSC) of two mobility controlled processes in the amorphous phas e of semicrystalline PEEK — enthalpy relaxation below the glass transition (T _g) and secondary crystallization aboveT _g. Both result in the observation of an endothermic peak just above the annealing temperature in the DSC scan of the polymer — the enthalpy recovery peak and the low temperature melting peak, respectively. There is a striking similarity in the time and temperature dependence of the endothermic peak for these two processes. These results are reminiscent of those obtained from small strain creep studies of physical aging of semicrystalline PEEK below and aboveT _g.We gratefully acknowledge support of this work by the National Science Foundation, Science and Technology Center for High Performance Polymeric Adhesives and Composites under DMR grant 91-2004 and by an NSF Young Investigator Award (DMR 93-57512).     

Synthesis and characterization of poly(ɛ-caprolactone-co-ethylene glycol) star-type amphiphilic copolymers by “click” chemistry and ring-opening polymerization

Abstract

The synthesis of poly(?-caprolactone-co-ethylene glycol) AAB star-type amphiphilic copolymers were carried out by use of a “click” chemistry reaction to block propargyl polyethylene glycol (propargyl-PEG) to terminally azide poly(?-caprolactone) (PCL-N₃). For this purpose, propargyl-PEG was synthesized by the reaction of PEGs (3000?Da, 2000?Da, 1500?Da, and 1000?Da) and propargyl chloride. Terminally chloride poly(?-caprolactone) (PCL-Cl) was carried out by means of ring-opening polymerization (ROP) of ?-caprolactone (CL) and 3-chloro-1,2-propanediol. Synthesis of PCL-N₃ was obtained by the chemical interaction of PCL-Cl and sodium azide. By reacting propargyl-PEG and PCL-N₃, the star-type amphiphilic copolymers were obtained. The characterization of products was accomplished by using multiple instruments including ¹H-NMR, FT-IR, GPC, TGA, contact angles, and elemental analysis techniques.     

Preparation,non-isothermal crystallization,and melting behavior of β-nucleated isotactic polypropylene/poly (ethylene terephthalate) blends

β-nucleated PP/PET blends were prepared using nano-CaCO₃ supported β-nucleating agent (β-NA), PP as matrix, and PET as dispersion phase. The effects of preparation methods, PET content, and melting temperature on the non-isothermal crystallization behavior and the melting characteristic and polymorphic composition of PP in the blends were investigated by differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). The results indicated that the PP crystallized predominantly in β-modification in the presence of β-NA. However, efficiency of β-NA for PP crystallization decreased with addition of PET and increasing PET contents. The β-nucleation of β-NA for PP crystallization in the blends was dependant on the preparation methods. The high β-nucleation and high β-PP content were obtained for PP/PET blend prepared at the temperature of 265 °C and added the β-NA into the blend at the temperature of 180 °C. However, the addition of β-PP or β-NA into blends at 265 °C decreased the β-nucleation, and no β-PP was formed because the β-NA mainly dispersed on the PET dispersion phase or at the interface between PP and PET.     

Non-isothermal crystallization, melting behavior and polymorphism of polypropylene in β-nucleated polypropylene/recycled poly(ethylene terephthalate) blends

β-Nucleated polypropylene (PP), non-compatibilized and compatibilized β-nucleated PP/recycled poly(ethylene terephthalate) (r-PET) blends were prepared on a twin-screw extruder. The compatibilizers were maleic anhydride grafted PP (PP-g-MA), glycidyl methacrylate grafted PP (PP-g-GMA), maleic anhydride grafted polyethylene-octene (POE-g-MA) and polyethylene-vinyl acetate (EVA-g-MA) elastomers. Effects of r-PET content, compatibilizer type and content, pre-melting temperature and time on the non-isothermal crystallization and melting behavior, and polymorphism of PP in the blends were investigated by differential scanning calorimeter (DSC). DSC results show that the crystallization temperature of PP crystallized predominantly in β-modification was higher than that of neat PP. In the non-compatibilized blend, PP matrix crystallized mainly in α-modification even if r-PET content was only 10 wt%. However, PP-g-MA compatibilization made PP matrix crystallize mainly in β-modification, but PP-g-GMA, POE-g-MA and EVA-g-MA did not improve the β-modification content distinctly. The α-crystal melting peak temperature of PP decreased with increasing pre-melting temperature, but r-PET content, compatibilizer type and content as well as pre-melting time had no obvious effect on the melting temperature of PP. The increase in PP-g-MA content, pre-melting temperature and time was benefit for the formation of β-modification. It is suggested that the β-nucleating agent is encapsulated or dissolved in polar r-PET in β-nucleated PP/r-PET blend, addition of PP-g-MA to the non-compatibilized blend resulted in transferring β-nucleating agent from r-PET phase into PP phase, the increase in PP-g-MA content, melting temperature and time was benefit for transferring β-nucleating agent from r-PET phase into PP phase. The non-isothermal crystallization kinetics of PP in the blends were evaluated by Mo’s method.     

Synthesis and Crystal Structure of α-( N-Protected a mino)β- lactam Derivative of 1 ,5-Benzothiazepine

１　ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｌｙ,ａｎｕｍｂｅｒｏｆｄｅｒｉｖａｔｉｖｅｓｏｆｂｅｎｚｏｔｈｉａｚｅｐｉｎｅｈａｖｅｂｅｅｎｐｒｅｐａｒｅｄａｎｄｓｔｕｄｉｅｄｆｏｒｔｈｅｉｒｐｈａｒｍａｃｏｌｏｇｉｃａｌａｃｔｉｖｉｔｉｅｓ〔１５〕．Ｉｎｏｕｒｐｒｅｖｉｏｕｓｗｏｒｋ,ｗｅｈａｖｅｉｎｃｏｒｐｏｒａｔｅｄｔｈｅβｌａｃｔａｍｒｉｎｇｉｎｔｏ１,５ｂｅｎｚｏｔｈｉａｚｅｐｉｎｅｂｙｒｅａｃｔｉｏｎｏｆ１,５ｂｅｎｚｏｔｈｉａｚｅｐｉｎｅｗｉｔｈｓｏｍｅａｃｙｌｃｈｌｏｒｉｄ…     

Synthesis and Crystal Structure of cis-[1,2-Bis(phenyl-thiomethyl)benzene]dichloroplatinum(Ⅱ)·0.5acetonitrile

1 INTRODUCTION The coordination chemistry of bithioethers with noble metal ions has received considerable attention for a very long time due to their appli- cations in extracting noble metals. A number of Pt(Ⅱ) complexes with such ligands have been reported[1～7], among which some crystal structures have been determined[4～7]. However, most of these structures are Pt(Ⅱ) complexes of a few bithioether ligands with flexible alkyl spacers, RS(CH2)nSR. To our knowledge, the crystal str…     

Synthesis of “bioinspired” copolymers: experimental and theoretical investigation on poly(vinyl benzyl thymine-co-triethyl ammonium chloride)

Abstract

“Bioinspired” copolymers based on vinylbenzyl thymine (VBT) and an ionically-charged monomer, such as vinylbenzyl triethylammonium chloride (VBA), were synthesized and theoretically investigated. These water-soluble copolymers are polystyrene- (PS) based, and their structure mimics DNA. In the presence of short-wavelength UV light, the thymine groups dimerize into non-toxic, environmentally benign, and biodegradable photo-resistant materials. Copolymerizations with different comonomer ratios were carried out at 65°C. Samples were taken along the reactions to determine monomer conversion, chemical composition, and molecular weight distribution. While average molecular weights fall along the reaction, the average composition remains almost constant and coincident with the initial comonomer ratios, thus indicating a similar reactivity of all the comonomer radicals. A mathematical model was developed that simulates the synthesis of the base biopolymer, in the sense of predicting the evolution of the global reaction variables and molecular structure of the polymer. The termination and propagation kinetic constants were adjusted to the experimental data. The resulting values are quite different to those of a normal styrene homopolymerization, thus suggesting a noticeable effect of the solvent and the comonomer pending groups.     

The Study of Nitric Oxide Adsorption and the Mechanism of Surface “Explosions” in the Reaction of CO + NO on Pt(100) and Pd(110) Single Crystal Surfaces

High resolution electron energy loss spectroscopy (HREELS), temperature-programmed desorption (TPD) and temperature-programmed reaction (TPR) were used to study NO adsorption and the reactivity of CO_ads and NO_ads molecules on Pd(110) and Pt(100) single crystal surfaces. Compared to the Pt(100)-(1 × 1) surface, the unreconstructed Pt(100)-hex surface is chemically inert toward NO dissociation into N_ads and O_ads atoms. When a mixed adsorbed CO_ads + NO_ads layer is heated, a so-called surface explosion is observed when the reaction products (N₂, CO₂, and N₂O) synchronously desorb in the form of sharp peaks with a half-width of 7-20 K. The shape specificity of TPR spectra suggests that the vacancy mechanism consists of the autocatalytic character of the reaction initiated by the formation an initial concentration of active sites due to partial desorption of molecules from the CO_ads + NO_ads layer upon heating to high temperatures. Kinetic experiments carried out on the Pd(110) surface at a constant reaction pressure and a linear increase in the temperature confirm the explosive mechanism of the reaction NO + CO.     

Synthesis and catalytic activity of Ln (III) complexes with an unsymmetrical Schiff base including multi“非汉字符号” C=N—groups

Complexes with the unsymmetrical Schiff base can be used effectively as the stimulated metal protein and catalyst with higher activity. In order to obtain an unsymmetrical bis-Schiff base, Elder[1] suggested that the nickel bis-Schiff base complex was prepared firstly, then the corre-sponding unsymmetrical bis-Schiff base was synthesized by stripping the ligand from this com-plex with dimethylglyoxime. The resulting product with an additional —NH2 group may be con-densed with another aldehy…     

A Simple “Green” Synthesis of Novel Bis(3-aryl-1,8-naphthyridin-2-yl)sulfanes and 2-(Methylthio)-3-aryl-1,8-naphthyridines under Microwave Irradiation and Conventional Conditions

Russian Journal of General Chemistry - An eco-friendly and highly efficient synthesis of substituted bis(3-aryl-1,8-naphthyridin-2-yl)-sulfanes and 2-(methylthio)-3-aryl-1,8-naphthyridines under...