White-light-emitting polymer diodes containing hole-injection/transport and electron-injection/transport layers were fabricated by solution processing using a blend of luminescent semiconducting polymers and organometallic complexes as the emission layer and water-soluble (or ethanol-soluble) polymers and/or small molecules as the hole-injection/transport layer and the electron-injection/transport layer. Illumination-quality light was obtained from these multilayer, high-performance devices, with stable Commission Internationale d'Eclairage coordinates, stable colour temperatures and stable, high colour-rendering indices, which were all close to those of 'pure' white light. 45 refs.

A brief report is presented on the creation by researchers at Peking University and the Ecole Normale Superieure in Paris of a superhydrophobic polymer structure by directly replicating the surface of a lotus leaf. The process involves a soft lithography method and casting of a polydimethylsiloxane layer on a leaf template.

The biodegradation of the above copolymer (PBSA) by Aspergillus versicolor isolated from compost was studied and its mechanism examined. Analysis of weight loss showed that more than 90% of PBSA film was assimilated within 25 days. There was also a rapid decrease in molec.wt. characterised by GPC. Several cracks and round holes were observed on the eroded film surface by SEM. These results showed the fast degradation of PBSA film in the presence of A.versicolor. For comparison, the hydrolysis of the same sample was much slower in the corresponding abiotic medium. The analyses by PMR and DSC indicated that the preferred degradation took place in the adipate units and that the succinate units were relatively resistant to A.versicolor. 20 refs.

Polymethyl acrylate(PMA)/ZnAl layered double hydroxide(LDH) intercalated nanocomposite was synthesised by in-situ bulk polymerisation of methyl acrylate(MA) with an organo-modified ZnAl-LDH(OZnAl-LDH). The TS of the nanocomposite was shown to increase dramatically as a result of the physical interaction between the layers of OZnAl-LDH and PMA chains. If measured at 10% weight loss, the decomposition temperature of PMA/OZnAl-LDH nanocomposite with 5 wt % OZnAl-LDH was about 17 degrees C higher than that of pure PMA or PMA/OZnAl-LDH microcomposite with 5 wt % OZnAl-LDH due to the strong interactions between the nanolayers of OZnAl-LDH and PMA chains. In the high temperature range, PMA/ZnAl-LDH had 39 wt % residues at 400C, which was 26 wt % higher than pure PMA. This was because the char with inorganic compounds was much stronger in retaining the polymer than that without inorganic compounds. 20 refs.

As a supplement to the paper by Gao et al. (ibid, 84, 2004, p.67-70), the error levels of the activation energy and pre-exponential factor by the 'h-constant method' were theoretically analysed and quantitatively assessed. It was demonstrated that the errors of the two kinetic parameters were attributable to the temperature integral approximations. The deduced error level gave a reasonable interpretation of the error values found by Gao et al. 9 refs.

Biopolymer chitosan/montmorillonite(MMT) nanocomposites were prepared in which MMT was used as nanofiller and dilute acetic acid was used as solvent for dissolving and dispersing chitosan and MMT. Morphology and properties of chitosan nanocomposites with and without acetic acid residue were studied in comparison with those of pure chitosan. The effect of acetic acid residue and MMT loading in nanocomposites was investigated. The X-ray diffraction and TEM results indicated the formation of an intercalated-and-exfoliated nanostructure at low MMT content and an intercalated-and-flocculated nanostructure at high MMT content. The thermal stability and the mechanical properties of the nanocomposites were characterised by TGA and nanoindentation. The nano-dispersed clay improved the thermal stability and enhanced the hardness and elastic modulus of the matrix systematically with the increase of clay loading. The existence of acetic acid residue in chitosan matrix affected its crystallinity, thermal stability and mechanical properties. 31 refs.

Tri(acryloyloxyethyl)phosphate(TAEP) was blended with methacrylated phenolic melamine(MAPM) in different ratios to give a series of UV-curable intumescent flame retardant resins. The cured TAEP/MAPM samples expanded significantly when burning. The expansion behaviour and flame retardance of the cured resins were characterised by the volume ratio after and before combustion and by limiting oxygen index(LOI). A distinct synergistic effect was found between TAEP and MAPM. The TAEP-0.30MAPM sample exhibited the highest degree of expansion and the highest LOI value. The degradation was monitored by TGA and in-situ FTIR spectroscopy. A degradation mechanism was proposed in which the phosphate group in TAEP first degraded to form polyphosphoric acids, which further catalysed the degradation of the material to form char with emission of nitrogen volatiles from MAPM, leading to the formation of expanding char. The morphological structures of crusts of the formed chars were observed by SEM, which demonstrated the synergistic effect between TAEP and MAPM. 22 refs.

Solutions of a rare earth modifier(RES, LaC13) and the epoxy chloropropane(ECP) grafting modification method were used for surface treatment of F-12 aramid fibres. The effects of RES concentration on the interlaminar shear strength(ILSS) of F-12 aramid fibre/epoxy composites were investigated and the fracture surfaces of ILSS specimens were analysed by SEM. It was shown that the RES surface treatment was superior to the ECP grafting treatment in promoting the interfacial adhesion between aramid fibres and the epoxy matrix. The TS of single fibres, however, was almost unaffected by the RES treatment. The optimum ILSS was obtained at a 0.5 wt % content of rare earth elements. 10 refs.

A phenylacetylene bearing a chiral L-alanine dipeptide moiety was synthesised and was polymerised by (2,5-norbornadiene)rhodium(I) chloride dimer into a high molec.wt. polymer in high yield. The chiroptical properties of the polymer were studied and the polymer chain was shown to exhibit a helical conformation with preferred handedness, which could be tuned by the solvent and temperature. The possibility of the polymer showing some interesting biological properties, such as biomimetic environmental adaptability and cell-growth-stimulating capability, is discussed. 25 refs.

A linear poly(N-isopropylacrylamide)(PNIPA) with beta-cyclodextrin(beta- CD) moiety was synthesised by the conjugation of beta-CD carrying amino groups (EDA-beta-CD) onto PNIPA with epoxy groups, number-average molec.wt.(Mn) 38,600, and the related reaction conditions were investigated. PNIPA-beta-CD was characterised by means of IR, NMR and UV spectroscopies, elemental analysis and DSC. The Mn and the beta-CD content of the PNIPA-beta-CD were 48,700 and 18.8 wt %, respectively. PNIPA-beta-CD could not only respond to temperature stimuli but also included guest molecules. Lower critical solution temperature of aqueous PNIPA-beta-CD solution was similar to that of PNIPA. The association constant for PNIPA-beta-CD with methyl orange was 2400 L/mol at pH 1.4, which was comparable with that of EDA-beta-CD. 46 refs.

Hyperbranched polymethacrylates were prepared by oxyanionic vinyl polymerisation of commercially-available monomers, including hydroxyethyl methacrylate(HEMA) and poly(ethylene glycol) methacrylate. Hyperbranched polymethacrylates with high molec.wt. were obtained using the complex of potassium hydride and 18-crown-6 as the initiator. The effect of 18-crown-6 was important and only oligomer could be obtained in the polymerisation without 18-crown-6. The molecular structure of the hyperbranched polymers was confirmed by PMR and carbon-13 NMR spectroscopies. The ratio of initiator to monomer significantly affected the structure of the resultant polymers. When the ratio of initiator to monomer was equal to 1 in the oxyanionic vinyl polymerisation of HEMA, the degree of branching of the resulting polymer was calculated to be about 0.49. 38 refs.

The surfaces of layered double hydroxides(LDHs) were modified with a long chain polymer, the polyethylene glycol derivative polyoxyethylene sulphate(PEGS), and intercalated nanocomposites were synthesised by a simple ion exchange method. The preparation, characterisation and properties of the modified PEGS/LDHs and sodium dodecyl sulphate/LDHs were studied. The assembly of PEGs did not affect the electrophoretic mobility of the LDHs particles. IR spectroscopic and TGA results indicated that few PEGS molecules adsorbed to the surface of LDHs, which made the system a useful modifier which could not result in the denaturation of proteins. 21 refs.

A quaternary ammonium tetraphenylborate salt containing the 4-(4'-benzoylphenyl)acetophenone chromophore was synthesised in a stepwise manner and characterised by FTIR, UV vis and proton NMR spectroscopy. The new compound, 4-(4'-benzoylphenyl)acetophenone-(1- azonia-4-azabicyclo(2.2.2)octane) tetraphenylborate (BPPAPG), is a photobase and photoradical generator with typical absorption wavelength of 250-350 nm. Following photolysis of BPPAPG, the formation of 1,4-diazabicyclo[2.2.2]octane was confirmed by mass spectrometry. BPPAPG was used as a photoinitiator for the free radical polymerisation of trimethylolpropane trimethacrylate, in which the known inhibiting effect of oxygen was absent, and as a photoinitiator for the UV-catalysed thermal curing of an epoxy resin. 20 refs.

The positive temperature coefficients (PTCs) of conductive silicone rubber were studied for rubbers containing three kinds of carbon black: BP 2000 superconductive, VXC-72 conductive and GPF 660. Methylvinylsilicone gum was compounded with carbon black and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane and vulcanised at 170 degC under 9.8 MPa, followed by thermal post-curing. The electrical resistances were determined and used to calculate the volume resistivities. The carbon black-rubber interactions were measured by bound rubber determination. The size of the PTC anomaly depended on the thermal expansion coefficient and the interaction between the silicone rubber and the carbon black. The effects of crosslinking on the temperature effect of resistivity depended on the type of carbon black. A weak interaction between carbon black and rubber gave a greater importance to the degree of crosslinking. 22 refs.

The liquid crystalline compounds 4,4'-diglycidyloxybiphenyl (BP) and hydroquinone bis(4-epoxypropylbenzoate) (HB) were mixed with fine particles of nanoclay colisite 93A in ethanol-chloroform (9:1) at 70 degC, cooled, ground down, then mixed with sulphanilamide (SAA) before thermal curing. The epoxy-organoclay nanocomposites were characterised by powder X-ray diffraction, DSC and polarised optical microscopy. BP diffused into the organoclay layers either in a solvent or in the molten state, increasing the d-spacing from 2.3 to 3.7 nm. The alkylammonium ions in the modified clay catalysed the epoxy ring-opening reaction with SAA. For organoclay contents less than 2 %, fast intergallery polymerisation formed an exfoliated nanocomposite but with 10% clay, an intercalated nanocomposite was formed because the amount of monomers was insufficient to diffuse into the clay gallery. With 5% organoclay, a mixture of both types was obtained. The cured composites with or without clay had the same liquid-crystalline phase as pure liquid-crystalline epoxy systems. 36 refs.

ABS blends were modified with styrene-acrylonitrile copolymer (SAN) and a series of polybutadiene-g-SAN (PB-g-SAN) impact modifiers and the changes in mechanical properties and morphologies were monitored. The graft copolymers containing 20.6-91.9 wt% PB were prepared by seeded emulsion polymerisation. The ABS content of the blends prepared by melt blending was maintained at 15 wt%. The blends were analysed by dynamic mechanical thermal analysis, impact strength and tensile measurements, TEM and SEM. For samples with a lower degree of grafting, the rubber particles were not completely covered by the SAN copolymers, leading to agglomeration. At higher grafting degrees, there was a uniform dispersion of rubber particles in the resin. The glass transition temperature decreased with increasing PB content of PB-g-SAN, whereas impact and yield strengths increased, then decreased, due to the changes in internal morphology. A PB/SAN ratio in the modifier of 71.7:28.3 gave the maximum impact and yield strengths. 15 refs.

Positively charged poly(methyl acrylate) (PMA)-silica nanocomposites were prepared from sol-gel precursors, synthesised from the coupling reaction of PMA with N-(3-(trimethoxysilyl)propyl)ethylenediamine (A-1120), followed by quaternisation with methyl iodide. The sol-gel precursors were hydrolysed in aqueous hydrochloric acid and dried on a heated plate to give the composite films. Polymers prepared with different proportions of PMA and A-1120 were characterised by FTIR and proton NMR spectroscopies, DSC, TGA and field emission SEM. The nanocomposites had glass transition temperatures 17-31 degC higher than PMA and lower thermal stabilities. FE-SEM confirmed that the nanoparticles were heterogeneously dispersed in the polymer matrix. The anion exchange capacities were 0.19-1.20 mmol/g, about half the theoretical values, and increased with increasing A-1120 content. 15 refs.