Search results for "Ethylene"
showing 10 items of 2589 documents
Study of polyethylene nanocomposites with polyhedral oligomeric silsesquioxane nanofillers—from structural characteristics to mechanical properties a…
2017
High-density polyethylene (HDPE) and low-density polyethylene (LDPE) nanocomposites filled with octakis({alkyl}dimethylsiloxy)octasilsesquioxanes (POSS) were prepared by the melt blending method. The effects of the structure and the content of POSS nanofillers on free-volume properties and structural characteristics of nanocomposites were investigated by the positron annihilation lifetime spectroscopy (PALS) and X-ray diffraction methods: wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). Incorporation of POSS nanofillers into polyethylene matrices modified the arrangement of the polymer chains and affected the size and number of free-volume holes in nanocomposites.…
Intercalation effects in LDPE/o-Montmorillonites nanocomposites
2007
Abstract Typical montmorillonite clays (Cloisite ® Na + , Cloisite ® 30B) were modified by treatment with octadecyl ammonium chloride (ODC) and successive additions of octadecylamine (ODA). XRD analyses of the modified clays indicated an increase of the basal spacing of the (0 0 1) planes depending on the ODC or ODA additions. Nanocomposites were prepared by dispersing the modified clays (3% w/w concentration) in LDPE, using a Brabender mixer. XRD measurements of the obtained products indicated in some cases the achievement of intercalation effects, which were confirmed by TEM analysis. Some thermal, mechanical, dynamic-mechanical and rheological properties were evaluated and correlated to …
Synthesis of Functional Block Copolymers Carrying One Poly(p-phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure
2016
Block copolymers composed of a MEH–PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxypoly(ethylene glycol)amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60–95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optic…
GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness
2018
International audience; Controlling the outer surface of nanometric metal–organic frameworks (nanoMOFs) and further understanding the in vivo effect of the coated material are crucial for the convenient biomedical applications of MOFs. However, in most studies, the surface modification protocol is often associated with significant toxicity and/or lack of selectivity. As an alternative, how the highly selective and general grafting GraftFast method leads, through a green and simple process, to the successful attachment of multifunctional biopolymers (polyethylene glycol (PEG) and hyaluronic acid) on the external surface of nanoMOFs is reported. In particular, effectively PEGylated iron trime…
Orthogonal functionalisation of upconverting NaYF4 nanocrystals.
2013
A simple and straightforward method for the orthogonal functionalisation of upconverting NaYF4 nanocrystals (UCNCs)-doped withYb(3+) and Er(3+)-based on N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide/N-hydroxysuccinimide (EDC/NHS) selective reactions between two dyes and two different reactive groups present at the periphery of the upconverting nanocrystals is reported. Organic-soluble UCNCs of 10 and 50 nm in size are encapsulated efficiently in a 1:1 mixture of two commercial 3000 Da poly(ethylene glycol) derivatives with two different reactive groups (amino and carboxylic groups). The water-dispersible UCNCs are non-cytotoxic, stable in the physiological environment, and present free ami…
Current rectification by nanoparticle blocking in single cylindrical nanopores.
2014
Blocking of a charged pore by an oppositely charged nanoparticle can support rectifying properties in a cylindrical nanopore, as opposed to the usual case of a fixed asymmetry in the pore geometry and charge distribution. We present here experimental data and model calculations to confirm this fundamental effect. The nanostructure imaging and the effects of nanoparticle concentration, pore radius, and salt concentration on the electrical conductance–voltage (G–V) curves are discussed. Logic responses based on chemical and electrical inputs/outputs could also be implemented with a single pore acting as an effective nanofluidic diode. To better show the generality of the results, different ch…
Effect of Polymer Length on the Adsorption onto Aluminogermanate Imogolite Nanotubes
2021
This study evidences the adsorption of model nonionic polymers onto aluminogermanate imogolite nanotubes, attractive porous nanofillers with potential molecular loading and release applications. We resolve the underlying mechanisms between nanotubes and polyethylene glycols with different molecular weights by means of nanoisothermal titration calorimetry. The analysis of the results provides a direct thermodynamic characterization, allowing us to propose a detailed description of the energetics involved in the formation of polymer/imogolite complexes. The affinity toward the nanotube surface is enthalpy-driven and strongly depends on the polymer chain length, which significantly affects the…
Determination of the electroactive area of graphite+polyethylene composite electrodes. Uncompensated resistance effects and convolution analysis of c…
1998
In this work, it is shown how the convolution analysis of chronoamperograms permits the observation of the uncompensated resistance and the natural convection effects on the electrochemical response of potassium ferrocyanide. The uncompensated resistance causes the current intensity to follow the Cottrell equation only after a certain critical time. The convolution of chronoamperograms worked out at different integration times shows a maximum when this time is long enough. The classical diffusion equations cannot explain this phenomenon themselves. The development of this maximum associated with the natural convection is discussed. If both these factors, the ohmic drop and the natural conve…
Evaluation of the healing of precoated vascular dacron prostheses.
1991
Knitted and woven Dacron grafts commercially coated with bovine collagen, gelatin and human albumin were implanted end-to-side between the infrarenal aorta and the bifurcation in 35 growing pigs. Grafts were explanted after 4, 8 and 12 weeks and compared to 6 uncoated knitted prostheses preclotted with blood that served as a control. Uncoated grafts rapidly developed a firmly attached neointima lined with endothelium. Compared with coated grafts the thrombus-free area of uncoated grafts was significantly larger (P less than 0.05). The slow resorption of albumin resulted in a delayed and incomplete neointimal healing and failing graft incorporation. Although the bovine collagen was only mini…
Oligosaccharide and Ganglioside Neuraminidase Activities of Mucolipidosis I (Sialidosis) and Mucolipidosis II (I-Cell Disease) Fibroblasts
1979
Fibroblasts cultured from the skin of patients with the genetic diseases mucolipidosis I and mucolipidosis II were found deficient in a neuraminidase specific for both an α23 and and α2 6 type of neuraminosyl linkage of sialyl oligosaccharides. Obligate heterozygotes (parents) showed an intermediate activity in mucolipidosis I, but a normal one in mucolipidosis II. The neuraminidase activity of mucolipidosis I fibroblasts towards gangliosides, measured at pH 4.5 in the presence of Triton X-100, was within the range of normal controls with gangliosides Gm3 and GD3, but somewhat diminished with a bovine brain ganglioside preparation. In mucolipidosis II, neuraminidase activity was markedly de…