Search results for "Ethylene"
showing 10 items of 2589 documents
Small angle scattering study of poly(methylmethacrylate)-blockpoly(ethylene oxide) block co-polymer in aqueous solution
2005
A combined Small Angle X ray (SAXS) and Neutron (SANS) Scattering study of aqueous solutions of a symmetric block copolymer consisting of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) moieties is presented. The polymer forms slightly polydisperse spherical micelles in a wide range of concentration (0.03 – 6.7 w/V) and temperature (20°C ≤ T ≤ 65°C). A good description of the SANS data is obtained using a polydisperse core-shell model with a structure factor for a modified hard sphere potential. By increasing the concentration at constant T we observed a decrease of the aggregation number and an increase of solvation of PEO groups in the shell, opposite to what happens by in…
2,4,5-Trimethylimidazolium Scaffold for Anion Recognition Receptors Acting Through Charge-Assisted Aliphatic and Aromatic C–H Interactions
2016
A series of two-armed 2,4,5-trimethylimidazolium-based oxoanion receptors, which incorporate two end-capped photoactive anthracene rings, being the central core an aromatic or heteroaromatic ring, has been designed. In the presence of HP2O7(3-), H2PO4(-), and SO4(2-) anions, (1)H- and (31)P NMR spectroscopical data clearly indicate the simultaneous occurrence of several charge-assisted aliphatic and aromatic C-H noncovalent interactions, i.e., significant downfield shifts were observed for the imidazolium C(2)-CH3 protons, the methylene N-CH2 protons, and the inner aromatic proton or the outer heteroaromatic protons. Density functional theory calculations confirm the occurrence of these non…
The antioxidant effect in controlling thermal degradation of a low density polyethylene blown film
2004
Abstract It is well known that antioxidants are widely used to prevent thermal degradation of high density and linear low density polyethylene. Antioxidants are not always present in low density polyethylene and only small amounts are usually added to these resins. In this work the effect of an antioxidant system on a low density resin having MFI (190 °C/2.16 kg)=2 g/10′ and density 0.9230 g/cm3 has been studied. Its effect on melt viscosity has been studied by means of a batch mixer and the torque vs time behaviour has been analysed. The results show that a maximum in the torque vs time curve can be seen for the material containing antioxidant. In contrast, the material without antioxidant…
Transfer of Some Alkyl Substituted Ferrocenes from Water to Cationic Surfactant Micelles Studied by Kinetic Method
1994
Abstract Binding of ferrocene and its 1,1′-dimethyl and n -butyl derivatives to dodecyl and tetradecyltrimethylammonium nitrate micellar aggregates has been studied at 20.0°C and ionic strength 0.02 tool dm -3 by examining the micellar retarding effects on the rates of iron(III) oxidation of these substrates. Solubilization of the ferrocenes in the cationic micellar phase increases as the substrate hydrophobic character increases and, to a lesser extent, as the surfactant hydrocarbon chain length becomes longer. The critical micelle concentrations of the surfactants used and the incremental free energy of transfer of methylene groups of both the substrate and the surfactant from the aqueous…
Rod-Length Dependent Aggregation in a Series of Oligo(p-benzamide)-Block-Poly(ethylene glycol) Rod-Coil Copolymers
2005
The synthesis of a series of rod-coil diblock copolymers with flexible poly(ethylene oxide) chains (M n = 5 000 g mol -1 ) and rod blocks consisting of monodisperse oligo(p-benzamide)s is described. The formation of defined supramolecular aggregates in solution as well as the solid state has been analyzed. The length of the oligo(p-benzamide)s has been systematically varied from n = 1 to 7 units. The influence of n on aggregation in chloroform and aqueous solution was investigated by GPC as well as UV-vis spectroscopy. A critical aggregation length was found for chloroform (n = 5) and water (n = 4), below which no aggregation is observed under otherwise identical experimental conditions. Ag…
Adsorption of triblock copolymers and their homopolymers at laponite clay/solution interface. Role played by the copolymer nature
2009
The adsorption thermodynamics of copolymers, based on ethylene oxide (EO) and propylene oxide ( PO) units, at the laponite (RD) clay/liquid interface was determined at 298 K. The copolymer nature was tuned at molecular level by changing the hydrophilicity, the architecture and the molecular weight (Mw) keeping constant the EO/PO ratio. Polyethylene (PEGs) and polypropylene (PPGs) glycols with varying Mw and their mixture were also investigated to discriminate the role of the EO and the PO segments in the adsorption process. Enthalpies of transfer of RD, at fixed concentration, from water to the aqueous macromolecule solutions as functions of the macromolecule molality were determined. They …
Sequestering Ability of Aminopolycarboxylic (APCs) and Aminopolyphosphonic (APPs) Ligands Toward Palladium(II) in Aqueous Solution
2014
The binding capacity of three aminopolycarboxylates [nitrilotriacetic acid (NTA), ethylene-glycol-bis(2-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA), and diethylenetriamine-N,N,N,NN-pentaacetic acid (DTPA)] and two aminopolyphosphonates {(1-hydroxyethane-1,1-diyl)bis(phosphonic acid) (HEDP) and [[(phosphonomethyl)imino]bis[2,1-ethanediylnitrilobis(methylene)]] tetrakis-phosphonic acid (DTPP)} toward palladium(II) ion was studied by potentiometric and spectrophotometric titrations at different temperatures (283.15 ≤ T/K ≤ 318.15) and ionic strengths (0.1 ≤ I/mol·dm -3 ≤ 1.0) in NaClO4. The hydrolysis of Pd2+ and the protonation of ligands were always taken into account in the speciation…
Oscillatory dynamics of the Belousov-Zhabotinsky system in the presence of a self-assembling nonionic polymer. Role of the reactants concentration.
2010
In the present study, the role played by the reactants concentration on the nonlinear response of a Belousov–Zhabotinsky (BZ) system to the addition of a self-assembling non-ionic polymer, poly(ethylene glycol) (PEG), has been assessed. The oscillatory parameters are influenced to an extent that significantly depends on the concentration of both the polymer and the Belousov–Zhabotinsky components. The effects obtained were attributed to the reaction among some of the BZ key species and the backbone and the alcoholic functional groups of the polymer, both in its monomeric and aggregated forms. Support to the proposed perturbation mechanism has been provided by performing numerical simulation…
Numerical Simulation of the Kinetics of Radical Decay in Single-Pulse High-Energy Electron-Irradiated Polymer Aqueous Solutions
2019
A new method for the numerical simulation of the radiation chemistry of aqueous polymer solutions is introduced. The method makes use of a deterministic approach combining the conventional homogeneous radiation chemistry of water with the chemistry of polymer radicals and other macromolecular species. The method is applied on single-pulse irradiations of aqueous polymer solutions. The speciation of macromolecular species accounts for the variations in the number of alkyl radicals per chain, molecular weight, and number of internal loops (as a consequence of an intramolecular radical-radical combination). In the simulations, the initial polymer molecular weight, polymer concentration, and do…
Consequences of linking charged and uncharged monomers to binary copolymers studied in dilute solution. Part II: Non-additivity effects in the viscom…
2017
Abstract Copolymers of ethylene oxide (EO) and N,N-dimethyl aminoethyl methacrylate (R) or [2-(methacryloyloxy)ethyl] trimethylammonium iodide (R+) were studied in dilute solution: P ( EO p – b – R n ) ( I ) , P(Rn(1−f) – ran – R+n f) ( II ) , and P ( EO p – b – R n + ) ( III ) ; n and p give the numbers of monomers and f is the degree of charging. For II (variable f) and III (variable n) the effects of charging on the intrinsic viscosities [η] are well described by Boltzmann sigmoids. The deviation of [ η ] from [ η ] add (calculated from the corresponding homopolymer data, assuming additivity of the individual contributions) are quantified by σ = [ η ] / [ η ] add - 1 measuring the segreg…