Effect of Ga- and BCl3-modified silica-supported [t-BuNSiMe2(2,7-t-Bu2Flu)]TiMe2/MAO catalyst on ethylene/1-hexene copolymerization

In this present study, the copolymerization of ethylene and 1-hexene was conducted over the [t-BuNSiMe₂(2,7-t-Bu₂Flu)]TiMe₂ (CGC)/MAO catalyst immobilized on different supports. The effects of Ga and the Lewis acid BCl₃ modification of the silica support on the copolymerization behavior were investigated based on catalytic activity and polymer properties. It was found that the silica support modified with BCl₃ exhibited the highest activity. However, both Ga and BCl₃ modifiers are capable of enhancing the catalytic activity, probably attributed to stronger interaction between the MAO and support together with the acidic sites exerted by the modification which could assist MAO to activate the catalyst during polymerization. Besides, a role of BCl₃ as a spacer to keep apart the catalyst on the silica surface was proposed as another probable reason for activity increased. This led to the more homogeneous-like behavior with less effect of support and also caused the higher comonomer incorporation content. Moreover, the results revealed that narrow polymer molecular weight distribution can be achieved by the supported CGC catalyst, especially for acidic modified supports. On the other hand, there was no noticeable effect with regards to the melting temperature and copolymer microstructure of the Ga and BCl₃ modification. Therefore, based on the study it may be regarded that the efficient supported CGC catalyst can be accomplished through the acidic modification namely Ga and BCl₃.     

Synthesis and properties of cationic ionomers from poly(ester‐urethane)s based on polylactide

l ‐Lactide (l ‐LA) was polymerized in the presence of N‐methyldiethanolamine as an initiator and Sn(Oct)₂ as a catalyst to give hydroxy‐telechelic poly(l ‐lactide) (PLLA‐diol) bearing a tertiary amine group at the center of the polymer chain. Successive chain extension of the PLLA‐diol with hexamethylene diisocyanate afforded PLLA‐based poly(ester‐urethane)s (PEU) with equally spaced tertiary amine groups. Treatment of the PEU with iodomethane converted tertiary amine groups to quaternary ammonium groups to give cationic ionomers (PEU‐MeI). The thermal, mechanical, hydrophilic, and biodegradation properties of the obtained polymers were investigated. The thermal properties of the PEUs and the PEU‐MeIs were similar each other. The PEU‐MeIs exhibited higher tensile modulus than those of the starting PEUs. The contact angles of water on the PEU‐MeIs were lower than those of the PEUs with similar NMDA content indicating their higher hydrophilicity. In compost degradation tests, the PEU‐MeIs showed slower degradation than those of the PEUs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4423–4428     

Synthesis and oxidative degradation of poly(ethene‐ran‐1,3‐butadiene)

Copolymerization of ethene and 1,3‐butadiene was conducted over SiO₂‐supported CpTiCl₃ catalyst using Ph₃CB(C₆F₅)₄ or B(C₆F₅)₃ combined with triisobutylaluminium (ⁱBu₃Al) or trioctylaluminium (Oct₃Al). When the copolymerization was carried out at 0°C, the Ph₃CB(C₆F₅)₄/ⁱBu₃Al and B(C₆F₅)₃/Oct₃Al systems selectively produced copolymers which contained about 0.5–2.5 mol‐% of trans‐1,4‐inserted butadiene units. The number‐average molecular weight (M_n) of the copolymers was around 80 000 with polydispersities in the range from 6 to 8. Oxidative degradation of the vinylene units with potassium permanganate decreased the M_n values to several thousands with polydispersities of ca. 2. This indicates that the butadiene units are randomly distributed in the copolymers. NMR analysis clarified that the decomposed product is a polyethene with carboxyl groups at both chain ends.     

Characterization of polybutadiene produced with CoBr2(PPh3)2-based catalysts

Polymerization of 1,3-butadiene was conducted with the CoBr₂(PPh₃)₂(Ph: phenyl)-methylaluminoxane (MAO) and MgCl₂-supported CoBr₂(PPh₃)₂-Al(CH₃)₃ catalyst systems. The microstructure of polybutadiene was analyzed in detail by ¹³C NMR spectroscopy after hydrogenation, which indicated that the distribution of the 1,2 and 1,4 units in polybutadiene is more random when the homogeneous CoBr₂(PPh₃)₂-MAO catalyst was used. The microstructure of these polymers was compared with that obtained using BuLi as catalyst.     

Gas chromatographic determination for forensic purposes of petroleum fuel inhaled just before fatal burning

The determination of petroleum fuel in the blood of burned bodies was carried out by three different gas chromatographic procedures. Seven components of gasoline (isopentane, n-pentane, 2-methylpentane, benzene, 2-methylhexane, 3-methylhexane and toluene) and five of kerosene (xylene, C9H20, mesitylene, pseudocumene and C11H24) were chosen as indicators with a coefficient of variation of 5-24%. The methods were applied to four autopsy cases with a relatively low carboxyhaemoglobin (HbCO) content. When gasoline exposure had occurred, the blood concentrations determined were almost identical whatever the components selected. Great variations in the components determined were found after kerosene exposure, and hydrocarbons greater than or equal to C14 were hardly inhaled by the victims. A higher content of fuel in the left than in the right ventricular blood observed in the autopsy cases suggests fuel inhalation just before death. The same phenomenon was also observed in the content of blood HbCO. Determinations of petroleum fuel and HbCO in both the right and left ventricular blood would be useful for the forensic diagnosis on burned bodies with a low HbCO content.     

Improved gas chromatography with electron-capture detection using a reaction pre-column for the determination of blood cyanide: a higher content in the left ventricle of fire victims

We developed a head-space method for the determination of blood cyanide by gas chromatography with electron-capture detection. In this technique, a reaction pre-column, packed with chloramine-T, was used for the conversion of hydrogen cyanide into cyanogen chloride. Since the reaction pre-column eliminated the necessity for trapping hydrogen cyanide from the biological samples, blood cyanide was quickly analysed by acidification only. The reaction pre-column was durable for at least several months. The calibration curve gave good linearity when dichloromethane was used as the internal standard, and the lower detection limit taken from this plot was ca. 0.05 micrograms/ml. The relative standard deviation of spiked blood samples was in the range 0.6-3.9%. We determined blood cyanide levels at autopsy in victims who had died from fire using this method. A significantly higher cyanide content was detected in the left ventricular blood than in the right. There was a positive correlation between blood cyanide and carboxylhaemoglobin contents. This simple and sensitive technique could be very useful for the determination of cyanide in various samples.     

Glucose-sensitive field-effect transistor with a membrane containing co-immobilized gluconolactonase and glucose oxidase

A glucose-sensitive field-effect transistor (FET) with a two-enzyme membrane containing gluconolactonase and glucose oxidase is investigated. The two-enzyme membrane (ca. 1 μm thick) is formed on the ion-sensitive gate of the FET by photopolymerization. The gluconolactonase used was a partially purified product prepared from crude glucose oxidase by gel filtration. A glucose sensor with only purified glucose oxidase has little response for glucose, but the co-immobilization of gluconolactonase and glucose oxidase considerably enhanced the response amplitude of the glucose sensor. The composition of the two-enzyme/photopolymer solution is optimized; gluconolactonase with an activity at least twice that of glucose oxidase is necessary. The linear calibration graph extends from 0.2 to 2 mM glucose.