ZrIV‐ und TaV‐Komplexe mit methanoverbrückten Bis(aryloxy)‐Liganden

Zr^IV and Ta^V Complexes with Methano‐Bridged Bis(aryloxy) Ligands The bis(aryloxy) ligand precursor compounds bis(2‐trimethylsiloxy‐5‐tbutylphenyl)methane (L–SiMe₃) and its bromoderivative (2‐trimethylsiloxy‐3‐bromo‐5‐tbutylphenyl)(2′‐trimethylsiloxy‐5′‐tbutylphenyl)methane (L^Br–SiMe₃) are prepared in analogy to the corresponding calixarenes in excellent yields. X‐ray structure analysis for L^Br–SiMe₃: space group P2₁/c, a = 12.462(7), b = 10.466(6), c = 23.315(14) Å, β = 105.02(4)°, V = 2937(3) ų, Z = 4. L–SiMe₃ and L^Br–SiMe₃ react with Zr^IV and Ta^V chlorides in very good yields forming di‐ and trinuclear complexes. From the reaction of CpZrCl₃ with L^Br–SiMe₃ in the ratio of 3 : 2 a Zr₃ complex ( 7 ) is obtained, with one L^Br ligand only, which Zr atoms are bridged by a μ₃‐oxygen. The X‐ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) Å, V = 23405(128) ų, Z = 18) additionally reveals that one phenolato oxygen atom of the L^Br ligand is terminally bound to a distorted tetragonal‐pyramidal coordinated Zr atom, while the second phenolato oxygen atom of the L^Br ligand forms a bridge to another Zr atom with a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination mode. The reactions of L–SiMe₃ and L^Br–SiMe₃ with CpTaCl₄ and TaCl₅ yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that in the Zr₃‐complex with one terminal and one bridging phenolato oxygen atom. The Zr₃ and the Ta complexes L^BrTa₂Cp₂Cl₆ and LTa₂Cl₈ were tested with respect to their catalytic properties in olefin polymerisation reactions in the presence of MAO.     

Synthesis and characterisation of star-shaped liquid crystalline polymer with a POSS core

The star-shaped POSS-graft-LCP with POSS as the core and liquid crystal polymer, poly{6-(4?-octyloxyphenyl-4″-benzoyl)hexyl acrylate}, as arms was prepared by atom transfer radical polymerisation technique using octa(3-chloropropyl) polyhedral oligomeric silsesquioxane [POSS-(CH₂CH₂CH₂Cl)₈] as initiator. For comparison, the linear liquid crystal polymer, poly{6-(4?-octyloxyphenyl-4″-benzoyl)hexyl acrylate} (LLCP), was obtained by conventional radical polymerisation. Both liquid crystal polymers were characterised by FT-IR, ¹H NMR, ¹³C NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarised optical microscopy and X-ray diffraction analysis. The liquid crystal phase behaviour research demonstrated that both liquid crystal polymers were reversible thermotropic nematic liquid crystal materials. The number of polymerisation degree of every arm attached on POSS in POSS-graft-LCP impacted greatly on the liquid crystal properties and only a small one was necessary for it to exhibit a broad liquid crystal range. Results further demonstrated that the special star-shaped topology of POSS and the eight arms attached helped POSS-graft-LCP form and stabilise liquid crystal phase easily. This research may further expand the way to star-shaped LCPs by employing a variety of (meth)acrylate and other vinyl liquid crystalline monomers.     

Preparation of Composite Polymer Particles by Seeded Dispersion Polymerization in Ionic Liquids

Summary: Submicron-sized monodisperse PS particles were prepared by dispersion polymerization of styrene in ionic liquids with poly(vinylpyrrolidone) as stabilizer. Seeded dispersion polymerization of MMA was subsequently carried out with PS seeds in [Bmim][BF₄] to prepare PS/PMMA composite particles. Observation of the obtained particles of ultrathin cross-sections with a scanning and transmission electron microscope revealed that no secondary nucleation occurred during the seeded dispersion polymerization and that the particles have a core-shell morphology consisting of a PS core and a PMMA shell. Successful preparation of PS/PMMA composite particles in an ionic liquid has thus been demonstrated. Moreover, PS/PAA (PS-core/PAA-shell) composite particles were prepared by seeded dispersion polymerization in [DEME][TFSI], illustrating that hydrophobic/hydrophilic composite particles can be readily prepared in the ionic liquid.     

Functionalised Microgels for Acrylic Coatings

Summary: Aqueous acrylic dispersions of hydroxy-functionalised copolymer microgel particles crosslinked with allyl methacrylate were synthesized by emulsion polymerization. The microgels were investigated as reactive polymer fillers in mixtures with a water-borne film-forming dispersion. Properties of coatings cast from mixtures of aqueous dispersion of hard microgel particles and film-forming water-borne dispersion were investigated. The swelling behaviour of microgels in selected solvents (aliphatic ketones) as a function of microgel composition is discussed as well. It was found that the swelling ability of microgels decreased with growing degree of crosslinking. Microgels comprising copolymerised butyl methacrylate swelled less in aliphatic ketones than microgels without this comonomer. This work was focused mainly on the influence of microgels incorporated in the commercial solvent-borne acrylic binders on the properties of coatings. It was shown that the application of microgels that were redispersed in acetone did not affect the surface appearance and transparency of coatings. Moreover, the presence of microgel network precursors accelerated film curing at ambient temperature and improved the final hardness of coatings.     

苯胺电化学聚合机理的研究

主要应用电化学方法研究了苯胺及其电化学聚合产物─—聚苯胺的循环伏安曲线，同时讨论了苯胺的存在对４－氨基二苯胺循环伏安曲线的影响。结果表明：随着苯胺聚合的进行，聚苯胺同时发生降解；苯胺电化学聚合按“白催化机理”进行。     

Preparation and characterisation of a novel fire retardant PET/α-zirconium phosphate nanocomposite

The preparation of a novel fire retardant nanocomposite of poly(ethylene terephthalate) (PET) using nanoscopic α-zirconium phosphate (α-ZrP), by in situ polymerisation was investigated. The novel fire retarded PET nanocomposite, PET-co-DDP/α-ZrP, was synthesized by the direct condensation of terephthalic acid, ethylene glycol, 9,10-dihydro-10[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP) and nano α-ZrP. The morphology, thermal stability and burning behaviour of the nanocomposite with 1 wt% α-ZrP loading was investigated. The extent of dispersion of the nanofillers was quantified by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Significant improvements in fire retardant performance were observed for the nanocomposite from limiting oxygen index (increased from 21.2 to 32.6), UL-94 (achieving V-0), and cone calorimetry (reducing both the heat release rate and the total heat released, without reducing the time to ignition).     

Direct synthesis of potentially biodegradable aromatic–aliphatic thermotropic copolyesters with photocrosslinking properties

ABSTRACT

In this study, aromatic–aliphatic thermotropic copolyesters derived from p-hydroxybenzoic acid, p-hydroxycinnamic acid (HCA), terephthalic acid and polyethylene glycol (PEG) with different molecular weight (200, 400, 600) were directly synthesised via Vilsmeier adduct solution polymerisation method. The structure, thermal behaviour, liquid crystal property, hydrophylicity and photoactivity were investigated by Fourier transform infrared and nuclear magnetic resonance spectroscopy, differential scanning calorimeter, polarised optical microscopy, water contact angle measurement and ultraviolet (UV) spectrophotometer. The PEG incorporation ratio is 0.540–0.691 related to the HCA units, because of its low reactivity. And, the copolyesters have relatively low melting temperatures (96–107°C) and good hydrophylicity (water contact angle value 61.2–75.3°) as compared with wholly aromatic thermotropic copolyester. All of the copolyesters exhibited nematic liquid crystal behaviour and the stable mesophase temperature range was more than 60°C after being melted. The resulted copolyesters had enough thermal stability for melt processing without any degradation. The UV absorption intensities decreased with increased irradiation time, indicating that photocrosslinking occurred.     

Anionic surfmers in mini-emulsion polymerisation

Mini-emulsion polymerisation of styrene or methylmethacrylate, initiated with ammonium persulphate, have been carried out, in the presence of hexadecane or of polymethylmethacrylate as hydrophobic costabilizer, and the simple hemiester of linear dodecyl alcohol and maleic anhydride, or polymerisable surfactants (surfmers) derived from the condensation of succinic anhydride and either hydroxy propylmethacrylate (MAES), or hydroxyethylmethacrylate (ABS). While the pure surfmers have not so good surface activity, from surface tension measurements, stable mini-emulsion droplets are obtained using a mixture with low amounts of SDS, which have diameters of about 100–200 nm, which remain stable upon polymerisation. Most of the surfmers remain grafted onto the particle surface, thus conferring to these particles strong stability in the various tests. However, due to the high water solubility of the surfmers, another part remains in the serum as unconverted monomer or water-soluble polymers. To cite this article: A. Guyot et al., C.R. Chimie 6 (2003).     

发射富里叶红外光谱法对氰酸酚酯树脂聚合的跟踪检测(英文)

本文研究了发射富里叶红外光谱对氨酸酚酯树脂聚合过程的跟踪检测技术。与目前普遍应用的透射红外光谱相对照，该方法给出可靠的结果。该技术尤其对低挥发性的树脂更适用。文中还讨论了有关光谱的获得及数据的处理问题。