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813 KiB

Open AccessArticle

Behavior of Na⁺-Polystyrene Sulfonate at the Interface with Single-Walled Carbon Nanotubes (SWNTs) and Its Implication to SWNT Suspension Stability

by Tabbetha Dobbins, Richard Chevious and Yuri Lvov

Polymers 2011, 3(2), 942-954; https://doi.org/10.3390/polym3020942 - 14 Jun 2011

Cited by 14 | Viewed by 9634

Abstract

The assembly of sodium polystyrene sulfonate (Na⁺-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na⁺-PSS adopts a spherically collapsed conformation [...] Read more.

The assembly of sodium polystyrene sulfonate (Na⁺-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na⁺-PSS adopts a spherically collapsed conformation believed to be the result of cation (either Na⁺ or H⁺) condensation onto the ionized polymer chain. It is well reported that cations (and also anions) adsorb preferentially onto single-walled and multi-walled carbon nanotube surfaces leading to an increased ion concentration in the near surface regions relative to the bulk solution. This work provides experimental evidence for preferentially absorbed cation condensation onto PSS anions until those cations are spaced at distances corresponding to the Bjerrum length ( _B), as defined by the Manning theory of ion condensation, at the SWNT surface. The resulting electrostearic repulsions allow the SWNTs to remain suspended for days. Furthermore , coulombic repulsion among SWNT bundles after cation adsorption alone is not sufficient to form stable suspensions—but rather the stearic repulsions associated with spherically collapsed PSS at the nanotube surface is responsible for suspension stability. It is believed that the ultrasonic agitation drives cations into the small spaces between SWNT bundles and coulombic potential attracts the PSS to those regions. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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334 KiB

Open AccessArticle

Using Light Scattering to Screen Polyelectrolytes (PEL) Performance in Flocculation

by Maria G. Rasteiro, Ineide Pinheiro, Fernando A. P. Garcia, Paulo Ferreira and David Hunkeler

Polymers 2011, 3(2), 915-927; https://doi.org/10.3390/polym3020915 - 27 May 2011

Cited by 19 | Viewed by 8008

Abstract

Flocculation of precipitated calcium carbonate (PCC) was monitored using light diffraction spectroscopy (LDS). Four cationic polyacrylamides of high molar mass and with different degrees of branching, all copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), were tested. LDS supplied information about the [...] Read more.

Flocculation of precipitated calcium carbonate (PCC) was monitored using light diffraction spectroscopy (LDS). Four cationic polyacrylamides of high molar mass and with different degrees of branching, all copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), were tested. LDS supplied information about the kinetic curves for flocs growth and also for the flocs structure evolution. Flocculation kinetics, flocs size and structure, flocs resistance and reflocculation capacity could be correlated with the degree of branching of the polyelectrolytes (PEL). Furthermore, PEL with different degrees of branching corresponded to different values for the intrinsic viscosity, indicating differences in the polymer conformation, which explained well the performance differences in flocculation. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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359 KiB

Open AccessArticle

Counterion Condensation and Effective Charge of PAMAM Dendrimers

by Ute Böhme, Anja Klenge, Brigitte Hänel and Ulrich Scheler

Polymers 2011, 3(2), 812-819; https://doi.org/10.3390/polym3020812 - 27 Apr 2011

Cited by 25 | Viewed by 8151

Abstract

PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino [...] Read more.

PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino groups which is monitored via the proton chemical shifts of the adjacent CH₂ groups. The effective charge is determined from a combination of diffusion and electrophoresis NMR. The fraction of the charges, which are effective for the interaction with an external electric field or other charges, decreases with increasing generation (size) of the dendrimers. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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530 KiB

Open AccessArticle

Polyelectrolyte Complex Nanoparticles of Poly(ethyleneimine) and Poly(acrylic acid): Preparation and Applications

by Martin Müller, Bernd Keßler, Johanna Fröhlich, Sebastian Poeschla and Bernhard Torger

Polymers 2011, 3(2), 762-778; https://doi.org/10.3390/polym3020762 - 12 Apr 2011

Cited by 50 | Viewed by 12043

Abstract

In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, [...] Read more.

In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, media and structural parameters. Especially, mixing order, mixing ratio, PEL concentration, pH and molecular weight, were found to be sensible parameters to regulate the size (diameter) of spherical PEI/PAC nanoparticles, in the range between 80–1,000 nm, in a defined way. Finally, applications of dispersed PEI/PAC particles as additives for the paper making process, as well as for drug delivery, are outlined. PEI/PAC nanoparticles mixed directly on model cellulose film showed a higher adsorption level applying the mixing order 1. PAC 2. PEI compared to 1. PEI 2. PAC. Surface bound PEI/PAC nanoparticles were found to release a model drug compound and to stay immobilized due to the contact with the aqueous release medium. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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484 KiB

Open AccessArticle

Phase Diagrams of the Aqueous Two-Phase Systems of Poly(ethylene glycol)/Sodium Polyacrylate/Salts

by Hans-Olof Johansson, Eloi Feitosa and Adalberto Pessoa Junior

Polymers 2011, 3(1), 587-601; https://doi.org/10.3390/polym3010587 - 09 Mar 2011

Cited by 61 | Viewed by 13885

Abstract

Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na₂SO₄, sodium adipate and sodium azelate) and salt concentrations on the position of [...] Read more.

Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na₂SO₄, sodium adipate and sodium azelate) and salt concentrations on the position of the binodal curve were investigated. The investigated PEG molecules had a molar mass of 2,000 to 8,000 g/mol, while that of NaPAA was 8,000 g/mol. Experimental phase diagrams, and tie lines and calculated phase diagrams, based on Flory-Huggins theory of polymer solutions are presented. Due to strong enthalpic and entropic balancing forces, the hydrophobicity of the added salt has a strong influence on the position of the binodal, which could be reproduced by model calculations. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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3974 KiB

Open AccessArticle

Polyelectrolytes: Influence on Evaporative Self-Assembly of Particles and Assembly of Multilayers with Polymers, Nanoparticles and Carbon Nanotubes

by Irina Marchenko, Alexey Yashchenok, Sergey German, Olga Inozemtseva, Dmitry Gorin, Tatiana Bukreeva, Helmuth Mohwald and Andre Skirtach

Polymers 2010, 2(4), 690-708; https://doi.org/10.3390/polym2040690 - 09 Dec 2010

Cited by 9 | Viewed by 11702

Abstract

Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte [...] Read more.

Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte multilayer coatings bring multifunctionality to spherical particles and planar films. Studying the construction of polyelectrolyte assemblies is convenient in the planar layout: it is reported here for incorporation of gold and magnetic nanoparticles as well as of carbon nanotubes. Gold nanoparticles concentration is controlled within the films. Potential applications of both spherical structures and planar films are highlighted. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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351 KiB

Open AccessArticle

Glucan Particle Encapsulated Rifampicin for Targeted Delivery to Macrophages

by Ernesto Soto, Yun Seong Kim, Jinhee Lee, Hardy Kornfeld and Gary Ostroff

Polymers 2010, 2(4), 681-689; https://doi.org/10.3390/polym2040681 - 06 Dec 2010

Cited by 64 | Viewed by 10362

Abstract

Glucan particles (GPs) are 2–4 mm spherical, hollow, porous shells extracted from Baker’s yeast, Saccharomyces cerevisae. The surface of the GPs is composed primarily of 1,3-b-glucan and the particles are efficiently phagocytosed via receptor-mediated cell uptake by macrophages, phagocytic cells expressing glucan receptors. [...] Read more.

Glucan particles (GPs) are 2–4 mm spherical, hollow, porous shells extracted from Baker’s yeast, Saccharomyces cerevisae. The surface of the GPs is composed primarily of 1,3-b-glucan and the particles are efficiently phagocytosed via receptor-mediated cell uptake by macrophages, phagocytic cells expressing glucan receptors. The hollow cavity of the GPs allows for efficient absorption and encapsulation of payload molecules. Rifampicin (Rif), a drug used in tuberculosis treatment, was encapsulated by precipitation in GPs and trapped using a calcium alginate or chitosan hydrogel to seal the pores of GPs and slow Rif release. Unplugged GP formulations immediately released Rif following particle resuspension in aqueous buffer. Alginate and chitosan sealing of GPs loaded with Rif was able to extend drug release for 24–72 h. GP-Rif formulations containing 10% w/w Rif/GP plugged with a calcium alginate hydrogel were effective at reducing colony forming units of M. tuberculosis strain mc²6020 in infected bone marrow macrophages ~80–90% at 24 and 72 hours. The amount of Rif delivered in the GP formulations was below the free Rif minimal inhibitory concentration demonstrating that GP targeted Rif delivery to macrophages enhances Rif antimicrobial effects. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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Review

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191 KiB

Open AccessReview

Biological and Biomimetic Comb Polyelectrolytes

by Thomas Andrew Waigh and Aristeidis Papagiannopoulos

Polymers 2010, 2(2), 57-70; https://doi.org/10.3390/polym2020057 - 26 May 2010

Cited by 9 | Viewed by 10112

Abstract

Some new phenomena involved in the physical properties of comb polyelectrolyte solutions are reviewed. Special emphasis is given to synthetic biomimetic materials, and the structures formed by these molecules are compared with those of naturally occurring glycoprotein and proteoglycan solutions. Developments in the [...] Read more.

Some new phenomena involved in the physical properties of comb polyelectrolyte solutions are reviewed. Special emphasis is given to synthetic biomimetic materials, and the structures formed by these molecules are compared with those of naturally occurring glycoprotein and proteoglycan solutions. Developments in the determination of the structure and dynamics (viscoelasticity) of comb polymers in solution are also covered. Specifically the appearance of multi-globular structures, helical instabilities, liquid crystalline phases, and the self-assembly of the materials to produce hierarchical comb morphologies is examined. Comb polyelectrolytes are surface active and a short review is made of some recent experiments in this area that relate to their morphology when suspended in solution. We hope to emphasize the wide variety of phenomena demonstrated by the vast range of naturally occurring comb polyelectrolytes and the challenges presented to synthetic chemists designing biomimetic materials. Full article

(This article belongs to the Special Issue Polyelectrolytes)

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