Search results for "ionic"
showing 10 items of 2016 documents
Ionic polymers based on dextran: hydrodynamic properties in aqueous solution and solvent mixtures.
2009
Hydrodynamic properties of a series of ionic polysaccharides with different charge density but the same molecular weight have been evaluated in salt-free aqueous solution and aqueous/organic solvent mixtures by means of capillary viscometry. The polyelectrolytes investigated contain quaternary ammonium salt groups, N-ethyl-N,N-dimethyl-2-hydroxypropylammonium chloride, attached to a dextran backbone. The experimental viscometric data have been plotted in terms of the Wolf method. The results show that the experimental data fit well with this model and allow the calculation of intrinsic viscosities and other hydrodynamic parameters, which provide new information about the dependence of the p…
Speciation of polyelectrolytes in natural fluids Protonation and interaction of polymethacrylates with major components of seawater.
2002
Acid–base properties of two sodium polymethacrylates (W= 4000 and 5400 Da) were studied potentiometrically in aqueous solution at 25 °C. Measurements were made in different salt solutions: LiCl 0.1–1.5, NaCl 0.1–2, KCl 0.1–2, Et4NI 0.1–0.75 mol l − 1 , and in artificial seawater in the salinity range 10 S 45. Protonation data were analysed by two different models and the dependence of the relative parameters on ionic strength were calculated. Measurements performed in interacting media (alkali metal chlorides and artificial seawater) were interpreted in terms of complex formation, and the relative formation parameters are reported. Previous data on the interaction of a higher molecular weig…
Solution properties of polyelectrolytes
1993
Abstract Aqueous size-exclusion chromatography was used to analyse the elution behaviour of several standard ionic polymers, including poly( l -glutamic acid), sodium poly(styrene sulphonate) and poly(acrylic acid), different in nature and chain flexibility, as a function of the pH and ionic strength of the eluent. Two organic-based hydrophilic packings, Spherogel TSK PW4000 and Ultrahydrogel 250, were tested in order to select the optimal conditions of macromolecular separation, and the results obtained for each column were compared. A set of calibration graphs for the above polyions as a function of eluent pH and ionic strength were obtained and compared with those obtained for uncharged …
Influence of dissolved humic material and ionic strength on C8 extraction of pesticides from water
1995
A mixture of twelve intermediate polarity pesticides, mostly carbamate-type, have been chromatographied on an octadecyl-silica bonded-phase column using acetonitrile-water gradient mobile phase and UV detection. Pesticides were extracted from aqueous matrix by solid-phase extraction. The extraction system consisted of a glass microcolumn containing octyl-silica solidphase conditioned with methanol and water. The elution was by acetonitrile-dichloromethane (50:50). Studies of extraction factors like volume of sample, addition of 10% sodium chloride and presence of dissolved humic material are investigated.
Solution properties of polyelectrolytes XII. Semi-quantitative approach to mixed electrostatic and hydrophobic polymer-gel interactions
1996
Abstract Aqueous size-exclusion chromatography of polyanions, where secondary effects affect the total separation mechanism, was investigated. For elution of polyelectrolytes on inorganic silica-based supports, the electrostatic polymer-gel repulsive interactions were evaluated through the values for a hypothetical repulsion layer, X e , according to the model developed by other workers. Using a similar procedure, the existence of an effective barrier defined as X e − X h is proposed for those systems in which electrostatic repulsion and hydrophobic interactions take place simultaneously as secondary mechanisms. X h can be viewed as a measure of the “enlargement” of the geometrical pore rad…
Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin
2012
Aqueous mixtures of γ-cyclodextrin (γ-CD) and the thermosensitive cationic diblock copolymer poly(N-isopropylacrylamide)-b-poly(3-acrylamidopropyl)trimethylammonium chloride (PNIPAAM24-b-PAMPTAM(+)9) or the PNIPAAM homopolymer PNIPAAM47 have been investigated using various experimental methods. Solid γ-CD–polymer inclusion complexes (pseudopolyrotaxanes) form at ambient temperatures in fairly concentrated CD solutions. The NMR measurements showed that the stoichiometry of the inclusion complexes is close to two NIPAAM units per CD molecule. The cationic block of the copolymer is not incorporated into the CD cavity. Synchrotron radiation X-ray diffraction spectra of the solid inclusion compl…
Polymerization of Mono- and Bi-functional Diacetylene Derivatives in Monolayers at the Gas-Water Interface
1979
The spreading and polymerization behaviour of long chain acids and phospholipid analogues containing diacetylene groups is described. Especially the polymerization in monolayers is followed spectroscopically with a new device used in connection with a commercial UV spectrometer. The polymerization is topochemically controlled. Sonification of the phospholipid analogues in water results in the formation of liposomes with multilayered membranes. Polymerization of the liposomes in water forms aqueous solutions of polymer vesicles.
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…
Kinetic studies of the interaction between DNA and polycations based on polyasparthylhydrazide
2008
Abstract In the present paper, a systematic kinetic study on the interaction between interpolyelectrolytes such as positive-charged polymers and DNA was carried out. In particular, a qualitative–quantitative kinetic investigation on the interaction between copolymers of the α,β-poly(aspartylhydrazide) and DNA calf thymus filaments was performed. This study gives a new model starting from a well known “pseudo-phase model”, and permits to give a qualitative explanation about the trends of experimentally observed kinetic constants by varying the concentration of one of the two poly-electrolytes. Moreover, this study permits to verify the dependence of the binding constants KPAHy–CPTA and KDNA …
Characterization of transparent silver loaded poly(l-lactide) films produced by melt-compounding for the sustained release of antimicrobial silver io…
2014
Abstract In the present study, thermally stable silver complexes were produced and incorporated into a poly-( l -lactide) (PLA) matrix by melt-compounding. The effect of the different formulations on the mechanical and color properties was first evaluated. Additionally, the release of silver ions to an aqueous environment was also monitored over time by anodic stripping voltammetry and correlated with the antimicrobial performance against Salmonella enterica. The incorporation of some silver compounds with contents of 1 wt% did not affect the mechanical or optical properties of the films. The films showed a good potential for application in surface treatment and demonstrated a sustainable, …