Search results for "electrolyte"

Fabrication of soft-etched nanoporous polyimide membranes for ionic conduction and discrimination

2021

Abstract Ionic selectivity in nanopores is usually based either on steric or charge exclusion mechanisms. By simultaneously incorporating both mechanisms into a functionalized membrane, an improved control over selectivity can be achieved. We describe the fabrication and experimental characterization of alkali metal cation-selective nanopores in heavy ion-tracked polyimide (PI) membranes using the soft-etching (SE) technique. The latent ion tracks in the PI membrane are selectively dissolved by an organic solvent to form tiny pores without affecting the bulk material. The ionic transport properties of SE-PI membranes are characterized using different electrolyte solutions containing alkali …

Cylindrical polyelectrolyte-comb-surfactant complexes

2006

Abstract Quaternized polymer combs based on poly(2-vinylpyridine-macromonomers) and the surfactant sodium dodecylsulfate are employed in the synthesis of a novel cylindrical polyelectrolyte-comb-surfactant complex (PECSC). The complex formed has 1:1 stoichiometry with respect to the ratio of dodecylsulfate to pyridinium units. It is soluble in organic solvents such as 2-butanol or chloroform. Characterization of single particle properties of the complex in organic solution is possible and yields a radius of gyration of 〈Rg〉z = 78.4 nm, a hydrodynamic radius of 〈1/Rh〉z−1 = 51.4 nm and a cross-sectional radius of Rg,cross = 3.9 nm in chloroform. The characteristic ratio γ = 〈Rg〉z/〈1/Rh〉z−1 de…

Polymersynthesen durch repetitive N-alkylierungen

1994

The repetitive N-alkylation reaction, at first used by Marvel, turned out to be a very versatile method for the synthesis of polycations. Rembaum introduced the name ionenes for this type of polymers. In the first part of the lecture some examples of single-stranded ionenes are described. The second part shows how the repetitive N-alkylation can be used for the synthesis of spiro polymers. In these double-stranded polymers two spiro-conjugated rings of the main chain have a central quaternary nitrogen in common (spiro-ionenes or spiro-azonia polymers)

Intrinsic viscosities of polyelectrolytes in the absence and in the presence of extra salt: Consequences of the stepwise conversion of dextran into a…

2011

Abstract Viscosities of dilute polymer solutions were measured in capillary viscometers for samples varying in their fraction f of charged units from 0.00 to 0.90. The dependence of the logarithm of the relative viscosity on polymer concentration c is in all cases reproduced quantitatively by three characteristic parameters: [ η ], the intrinsic viscosity; B , a viscometric interaction parameter (related to the Huggins constant); [ η ] , a parameter required only for polyelectrolytes at low concentrations of extra salt. In pure water [ η ] increases more than 80 times as the fraction f rises from zero to 0.90 and [ η ] starts from zero and goes up to ≈71 mL/g. Upon the addition of NaCl [ η …

Some examples of the modification of polymers

1986

Reactions avec des groupes amide et amino dans la chaine principale, et avec un groupe terminal bromoacetyl. Polymerisation de la conidine en presence d'un polystyrene vivant

Surfactant-Induced Helix Formation of Cylindrical Brush Polymers with Poly(L-lysine) Side Chains

2008

The complex formation of oppositely charged surfactants with some polypeptides is known to induce β-sheet or helix formation. Here, we report on the complex formation of cylindrical brush polymers with poly(L-lysine) side chains and sodium dodecylsulfate (SDS). With increasing amount of added surfactant the cylindrical polymers first adopt a helical conformation with a pitch of approximately 14-24 nm followed by a spherically collapsed structure before eventually precipitation occurs. CD measurements suggest that the helix formation of the cylindrical brush polymers is driven by the hydrophobicity of the ,8-sheets formed by the PLL side chain-SDS complexes.

Cyclodextrins in polymer synthesis: Free radical polymerization of cyclodextrin complexes withN-methacryloyl-11-aminoundecanoic acid orN-methacryloyl…

1998

The hydrophobic monomers N-methacryloyl-11 -aminoundecanoic acid (1) or N-methacryloyl-1-aminononane (2) were incorporated as guests into the cavity of heptakis(2,6-di-O-methyl)-β-cyclodextrin (Me 2 -β-CD) as a host, yielding the water compatible monomers N-methacryloyl-l 11-aminoundecanoic acid/ Me 2 -β-CD-complex (1a) and N-methacryloyl-1 -aminononane/Me 2 -β-Cl complex (2a). These complexes were polymerized radically in aqueous medium. The resulting polymers 1b and 2b which were obtained from the complexes 1a and 2a, are insoluble in water because of the unthreading of the cyclodextrin during the polymerization. The polymerization rate of 1a and 2a is high in comparison to the rate of th…

Synthesis, characterisation and properties of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsiv…

2009

Abstract A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly( N -2-hydroxyethyl)- dl -aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance ( 1 H NMR), Fourier-Transformed Infrare…

1995

Polystyrene-block-poly-1-azabicyclooctane[4,2,0] has been modified by protonation or alkylation of the polyamine moiety. Short chain alkyl iodides lead to quantitatively quarternized products while longer alkyl chains or alkyl-bromides give incomplete conversion. The viscosimetric behavior of the charged blockcopolymers is dominated by the polyelectrolyte block although the polyelectrolyte effect is drastically reduced by the presence of the polystyrene block. The blockcopolymers are insoluble in water, but concentrated solutions of the polymers in DMF can be diluted with any amount of water without any precipitation. Although the blockcopolymers have an amphiphilic structure they do not ex…

Cationic copolymers of ?,?-poly-(N-2-hydroxyethyl)-DL-aspartamide (PHEA) and ?,?-polyasparthylhydrazide (PAHy): synthesis and characterization

2000

In the present study the derivatization of two water-soluble synthetic polymers, α,β-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) and α,β-polyasparthylhydrazide (PAHy), with glycidyltrimethylammonium chloride (GTA) is described. This reaction permits the introduction of positive charges in the macromolecular chains of PHEA and PAHy in order to make easier the electrostatic interaction with DNA. Different parameters affect the reaction of derivatization, such as GTA concentration and reaction time. PHEA reacts partially and slowly with GTA; on the contrary the reaction of PAHy with GTA is more rapid and extensive. The derivatization of PHEA and PAHy with GTA is a convenient method to introdu…