环境样品中苯系物的溶剂蒸气吹扫-吸收GC-MS分析法

建立了一种简易而有效的溶剂蒸气吹扫 -吸收样品处理技术 ,适用于分离富集复杂水样和固体/半固体样品中苯系物等挥发性有机物。样品在汽提装置中被含有有机溶剂蒸气(CH2Cl2 或CS2)的氮气流处理 ,进入洗脱气流的挥发性有机物用有机溶剂(CH2Cl2 或CS2)吸收。样品处理过程不存在乳化问题 ,样品有机溶液可直接用于GC -MS分析。苯系物检出限为0.05μg/L或0.1×10-9 。     

Atomic force microscopic studies of novel arborescent block and linear triblock polystyrene-polyisobutylene copolymers

This paper reports the investigation of the nanostructured surface morphology of novel arborescent polyisobutylene-block-polystyrene (PIB-PS) copolymers, in comparison with linear PS-PIB-PS triblock copolymers, using atomic force microscopy (AFM) in tapping mode. Arborescent PIB-PS samples displayed interesting new phase morphologies, which changed dramatically upon annealing but remained irregular. Linear PS-PIB-PS samples showed morphologies similar to those previously found by transmission electron microscopy (TEM) in cryomicrotomed bulk samples, ranging from spherical/cylindrical to lamellar nanometer-sized discreet PS phases dispersed in a continuous PIB matrix. Annealing the samples resulted in more ordered structures.Three-dimensional AFM image and section analysis indicated a height difference between PIB and PS in the block copolymers, which became more prominent during annealing. This feature was verified on compression moulded and protein coated samples. The arborescent PIB-PS materials displayed thermoplastic elastomeric behaviour with a tensile strength between 7 and 10 MPa and elongation ranging from 1000% to 1830%. In comparison, linear triblock samples had a tensile strength between 7 and 20 MPa and elongation ranging from 380% to 640%. Block copolymers with irregular elastomeric midsegments may emerge as a new class of TPEs.     

Atom transfer radical polymerization of 1-phenoxycarbonyl ethyl methacrylate monomer

Atom transfer radical polymerization conditions with copper(I) bromide/2,2^′-bipyridine (Cu/2,2^′-bpy) as the catalyst system were employed for the homopolymerization and random copolymerization of 1-phenoxycarbonyl ethyl methacrylate (PCMA) with methyl methacrylate (MMA). Temperature studies indicated that the polymerizations occurred smoothly in bulk at 110 °C. Poly(PCMA)(polydispersity index=1.27) homopolymer was characterized and then used as macroinitiator for increasing its molecular weight. The homopolymerization of PCMA was also carried out under free radical conditions using 2,2^′-azobisisobutyronitrile as an initiator.The monomer and polymers were characterized by FT-IR and ¹H and ¹³C-NMR techniques. The glass transition temperatures, the solubility parameters and average-molecular weights of the polymers were determined. Thermal stabilities of the polymers were given as compared with each other by using TGA curves. Thermal degradation products of poly(PCMA)s obtained by ATRP and free radical polymerization were compared with each other by using ¹H-NMR technique.     

Solvent effect in cis-1,4 polymerization of 1,3-butadiene by a catalyst based on neodymium

In this work a laboratory polymerization scale process was studied for the production of polybutadiene with high content of cis-1,4 repeating units. A Ziegler-Natta catalytic system based on neodymium versatate (catalyst), diisobutylaluminium hydride (cocatalyst) and tert-butyl chloride (chlorinating agent) was used. The influence of solvent nature (pure grade) and possible contaminants (electron donors) in a recovered solvent from a butadiene-styrene anionic polymerization industrial plant on the stereoselectivity and catalytic activity, molecular weight and molecular weight distribution of the resultant polybutadienes was studied. The polymers were characterized by infrared spectroscopy and size exclusion chromatography. Polybutadienes with cis-1,4 units content in the range of 99-98% were produced. The polymers weight-average molecular weight, , varied from 2.23 × 10⁵ to 4.47 × 10⁵ and the molecular weight distribution, MWD, from 3.1 to 5.1.     

Cationic polymerization of dienes VII. New electron donors in the polymerization of 1,3-pentadiene initiated by aluminum trichloride in non-polar solvent

The aim of this research was to investigate new bulky electron donors (EDs) generating hindered active species in the cationic polymerization of 1,3-pentadiene initiated by AlCl₃ in pentane, in order to avoid or strongly reduce the reaction between the active species and the double bonds of the polymer which are responsible for side reactions. At room temperature, the polymerization in the presence of new ED, such as OPh₂, N(PhBr)₃, NPh₃ and SPh₂, allowed to obtain higher conversions and lower insoluble fractions than without electron donor. The formation of a complex ED/AlCl₃ was shown for each electron donor. However, in the case of NPh₃ and SPh₂, variations of the polymer microstructure demonstrated an interaction between active species and these EDs. Similar results were obtained at lower temperature (−10 °C). The beneficial effect of the presence of electron donors such as NPh₃ and SPh₂ demonstrated the validity of the concept of sterically hindered active species, but the polymerization was still uncontrolled.     

Synthesis and thermal decomposition of lanthanide hexacyanochromate(iii) complexes,Ln[Cr(CN)6]·nH2O (Ln=La-Lu; n=3, 4)

New solid complex of nitrilotriacetic acid and bismuth trichloride was synthesized by a solid phase reaction of nitrilotriacetic acid and bismuth trichloride at room temperature. The composition of the sample is BiCl₃[N(CH₂COOH)₃]_2.5. The crystal structure of the complex belongs to triclinic system with the lattice parameters: α=0.7849 nm, β=0.9821 nm, χ=2.0021 nm, α=96.50°, β=98.76° and γ=90.49°. The far-infrared spectra show the bonding between the Bi ion and N atom of nitrilotriacetic acid. The thermal analysis also demonstrates the complex formation between the bismuth ion and nitrilotriacetic acid. The gaseous pyrolysis product and the final residue in the thermal decomposition process are determined to check the thermal decomposition reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Surface modification of polypropylene microfiltration membranes by graft polymerization of N-vinyl-2-pyrrolidone

A hydrophilic polymer, poly(N-vinyl-2-pyrrolidone), was tethered on the surface of polypropylene microfiltration membrane (PPMM) by UV photo-assisted and γ-ray pre-irradiation induced graft polymerizations. Results revealed that the γ-ray pre-irradiation graft polymerization was more efficient in view of the grafting degree. The chemical changes of the membrane surface were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Pure water contact angle on poly(N-vinyl-2-pyrrolidone)-grafted PPMM decreased with the increase of grafting degree, which indicated an enhanced hydrophilicity for the modified membrane. Both bovine serum albumin adsorption and static platelets adhesion were measured to evaluate the bio-compatibility of the poly(N-vinyl-2-pyrrolidone)-modified PPMM. The statistical amounts of adsorbed bovine serum albumin and adhered platelets on unit membrane area decreased significantly, which to a certain degree demonstrated that the hemocompatibility of PPMM was improved. The N₂ permeability and the mean pore diameters of different PPMMs increased at first, then decreased after certain grafting degree. The changes of water flux followed a similar tendency. These indicated that at low grafting degree pore degradation induced by γ-ray irradiation had a major impact on permeability, while this was overcompensated by the grafted polymer at high grafting degrees.     

Enzymatic ring-opening polymerization of 2,2-dimethyltrimethylene carbonate catalyzed by PPL immobilized on silica nanoparticles

Silica nanoparticles were first used as the carrier for the porcine pancreas lipase (PPL) immobilization. The result of transmission electron microscopy (TEM) showed that the immobilized lipase was still in nanosize after enzyme immobilization. The ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) catalyzed by this immobilized PPL (IMPPL) was explored. ¹H NMR spectra suggested no evidence of decarboxylation during propagation. Influences of IMPPL concentration and reaction temperature on the molecular weight and yield of poly(DTC) were studied. The recovery and reuse of IMPPL for the ring-opening polymerization of DTC was also investigated. The recycling IMPPL showed even higher catalytic activity and a higher molecular weight of polycarbonate could be achieved.     

Synthesis of well-defined polymers with protected silanol groups by atom transfer radical polymerization and their use for the fabrication of polymeric nanoparticles

Copper-mediated atom transfer radical polymerization (ATRP) of a protected silanol group-holding methacrylate, methacryloxypropyltrimethoxysilane (MOPS), was investigated. In a dry condition using carefully distilled solvent and monomer, the polymerization proceeded in a living fashion providing a low-polydispersity polymer with a predicted molecular weight. The ATRP in conjunction with the sequential monomer addition of methyl methacrylate (MMA) and MOPS afforded a block copolymer of the type PMMA-b-poly(MMA-r-MOPS). The heat treatment of a solution of the block copolymer in the presence of a catalytic amount of ammonia gave a polymeric core-shell nanoparticle with a shell of PMMA moieties and a core of the poly(MMA-r-MOPS) blocks cross-linked via the condensation of the trimethoxysilane groups of the MOPS moieties.