Polyelectrolyte Block Research Articles

Fusion of Charged Block Copolymer Micelles into Toroid Networks

The association behavior of polyelectrolyte block copolymers in aqueous solution as a function of polymer and salt concentration is investigated for poly(ethylethylene-b-styrenesulfonic acid) (PEE-PSSH). This copolymer combines a soft hydrophobic block with a highly charged polyelectrolyte block that allows direct dissolution in aqueous solutions to investigate micellization under equilibrium conditions. Increasing polymer and salt concentration leads to the fusion of polyelectrolyte micelles into vesicles and fractal toroid-micronetworks. Association structures were characterized by static light scattering (SLS), small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). At high salt concentrations the solution phase separates into a dilute micellar phase and a concentrated gel phase.

Neutron Reflectivity of Adsorbed Water-Soluble Block Copolymers at the Air/Water Interface: the Effects of Composition and Molecular Weight

We have used neutron reflection to follow the effects of composition and molecular weight on the structure of layers of poly(2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate) copolymer (poly(DMAEMA-b-MMA)) adsorbed at the air/water interface. We had previously shown that for a 70% DMAEMA copolymer of M n about 10K at a pH of 7.5 there is a surface phase transition from a layer about 20 A thick to one about 40 A thick and that the adsorbed layer at the higher concentration has a layered cross-sectional structure with the most hydrophobic part of the polymer forming a central layer rather than the outer layer in contact with air, as would be expected. The present work shows that copolymers containing 80% DMAEMA (about the same M n ) and 70% DMAEMA (M n about 20K) form the same layered structure at the surface. The 80% DMAEMA copolymer is more surface active than the 70% copolymer, and this parallels the tendency to aggregate into micelles in bulk solution. The increase in molecular weight from 10K to 20K decreases the surface activity of the 70% DMAEMA copolymer. Addition of electrolyte enhances the formation of the layered structure at the interface but tends to equalize the surface activities of the three copolymers. Other surprising features are the increase of surface activity with increasing polyelectrolyte block size when the block is the larger component and the apparent suppression of ionization in the surface region.

Diffusive Radical Entry as the Rate-Determining Step in Amphiphilic Block Polyelectrolyte Mediated Emulsion Polymerization

The amphiphilic water soluble block polyelectrolytes PMMA-b-SPGMA and PMMA-b-QPDMAEMA are efficient surfactants for the radical emulsion polymerization. Negatively charged, neutral, and positively ...

Synthesis of amphiphilic polyelectrolyte block copolymers using "living" radical polymerization. Application as stabilizers in emulsion polymerization

This paper describes the synthesis of amphiphilic block copolymers composed of an ionic poly(styrenesulfonate) first segment and a hydrophobic polystyrene second one, using TEMPO-mediated “living” radical polymerization. These copolymers proved to be efficient stabilizers in the emulsion polymerization of styrene.

Synthesis of amphiphilic polyelectrolyte block copolymers using “living” radical polymerization. Application as stabilizers in emulsion polymerization

Synthesis of amphiphilic polyelectrolyte block copolymers using “living” radical polymerization. Application as stabilizers in emulsion polymerization

Synthesis of Nanoporous Silica with New Pore Morphologies by Templating the Assemblies of Ionic Block Copolymers

Mesoporous silicas with variable pore size and architecture were made by using aqueous solutions of block copolymers with one polyelectrolyte block as templates in a sol-gel process. Pore size and connectivity follow the structure of the block copolymer micelles or mesophases, i.e., the resulting silica gel network is a precise copy of the original self-assembly structure. In this paper, three cationic polybutadiene-b-poly(vinylpyridinium) block copolymers as well as an anionic poly(ethylethylene)-b-polystyrenesulfonate block are utilized as structure-directing media. Depending on the relative block lengths and the salt content in the reaction mixture, different aggregation structures are obtained, leading to well-defined spherical pores in the size range between 10 nm < ξ < 50 nm or more complex architectures, such as “rattles”, the casts of multilamellar vesicles. It is proposed that it is possible to use this precise silica casting procedure in order to depict and characterize unknown aggregation structures of block copolymers. Therefore silica casting appears to be a considerable alternative to the more tedious freeze-fracture preparations of similar colloidal systems.

Polyelectrolyte Brushes Grafted at the Air/Water Interface

A new approach for the study of grafted polyelectrolytes is investigated: monolayers at the air/water interface of block copolymers consisting of a liquid hydrophobic and a polyelectrolyte block. ...

Stabilization of aqueous α‐Al2O3 suspensions with block copolymers

AbstractWater‐soluble diblock copolymers (DBCPs) with a polyelectrolyte block are accessible by sequential anionic polymerization of tert‐butylmethacrylate (TBMA) and ethylene oxide (EO), followed by polymer analogous conversion of the PTBMA into poly(methyacrylic acid) (PMAA) blocks. These materials are highly efficient dispersants for oxide ceramic powders in aqueous media. A series of block copolymer samples with Mn ranging from 1300 to 38 900, and (EO:MAA) block length ratios from 0.5 to 11.7 were prepared with polydispersities close to 1.2. The influence of overall molecular weight and block length ratio, pH and ionic strength on the stability of aqueous α‐Al2O3 suspensions was investigated by sedimentation and adsorption experiments, surface plasmon resonance (SPR) and electrokinetic measurements. The copolymers are capable of stabilizing alumina suspensions by a combination of specific adsorption of one block on the particle surface and a shielding effect provided by the nonadsorbing block. In addition, the adsorption of the negatively charged PMAA block on the oppositely charged alumina surface reverses the electrophoretic potential of the oxide particles, a process which is strongly pH dependent. With respect to the powder dispersing efficiency, an optimum was found when the DBCP consisted of a short PMAA anchoring and an approximately tenfold longer PEO stabilizer block with an overall molecular weight of about 5000. Alumina suspensions with the DBCP added were highly dispersed and rather stable against salt addition in a much wider pH window than block‐copolymer‐free suspensions.

Soluble Complexes from Poly(ethylene oxide)-block-polymethacrylate Anions and N-Alkylpyridinium Cations

Complexes from poly(ethylene oxide)-b-poly(sodium methacrylate) (PEO-b-PMANa) and N-alkylpyridinium bromides are water soluble, in marked contrast to those from poly(sodium methacrylate). These systems are studied using potentiometric titration, microcalorimetry, ζ-potential measurement, light scattering and electron microscopy. Three regions (A−C) are observed with a complex from PEO-b-PMANa and cetylpyridinuim bromide (C16PyBr) when the composition of the mixture (Z = [C16PyBr]/[COO-]) is varied. (A) At Z < 1 C16PyBr binds electrostatically to the polyion to form soluble complex with a negative ζ-potential. (B) The size of the complex decreases and reaches minimum (o.d. 67 nm) at Z = 1 when ζ = 0. Those stoichiometric complexes are soluble and stable. They appear to be micelles with a core formed by C16PyBr neutralized polyion chains and a shell of PEO chains. (C) With a further increase in Z, the surfactant cations incorporate in the particles (ζ > 0). The particles formed at saturating concentrations of C16PyBr are spherical and remarkably monodisperse. Overall, these systems represent a new class of lyophilic colloids that exhibit combined properties of amphiphilic block copolymers and polyelectrolyte−surfactant complexes.

Polyelectrolyte Block Copolymers as Effective Stabilizers in Emulsion Polymerization

Amphiphilic block copolymers consisting of hydrophobic block of hydrogenated polybutadiene and a partly sulfonated polyelectrolyte block of poly(styrenesulfonate) are effective stabilizers in emulsion polymerization. At low relative amounts of block copolymer (0.4 wt % as a fraction of monomer weight) and salt-free conditions, well-defined and stable latices with particle diameters of ca. 100 nm and solid contents of 20 wt % are obtained. This high stabilization efficiency of optimized block copolymer systems enables the formulation of latex systems with a relatively low remaining polarity in solid films and offers new interesting model systems with exclusively electrosteric stabilization. A comparison of polymerization in high or low ionic strength solution and the variation of the degree of sulfonation of the poly(styrenesulfonate) block shows an optimum stabilization of the latices at low ionic strength during polymerization. Fully sulfonated polymers systems presumably show a molecular orientation perpendicular to the particle surface, whereas 50% sulfonated species take on a traillike conformation along the surface, which is explained by remaining hydrophobic interactions. Due to this multiple surface particle contacts, the application of partly sulfonated polymers leads to more effective stabilization. At higher stabilizer concentrations, aggregates are found, which can be redispersed by ultrasonification or addition of low molecular weight surfactant solution.

Adsorption of Hydrophobically Modified Polyelectrolytes on Hydrophobic Substrates

A series of diblock copolymers, poly (tert-butyl styrene)-sodium poly (styrene sulfonate) with different molecular weight and percentage of sulfonation have been used to study the effect of polymer structure on its adsorption behavior onto hydrophobically modified silicon wafers. The percentage of the hydrophobic block varies from 3. 6-8. 9%. Previous studies show that salt concentration is very important for the adsorption of such polyelectrolytes onto silica surfaces. Octadecyltriethoxysilane (OTE) has been used to modify the silicon wafer which changes the water contact angle from 50° on unmodified silica to 100° to 120°. On this hydrophobic surface, we found that the adsorption of these slightly hydrophobically modified polyelectrolytes is close to the 4/23rd power of salt concentration predicted by a recent model. The grafting density is also consistent with a dependence on the length of the hydrophobic block to the -12/23rd power, and the length of the polyelectrolyte block to the -6/23rd power, predicted by this model.

Block polyelectrolytes in aqueous environments

AbstractAnalogous to the self‐assembly of low‐molecular‐weight amphiphiles in aqueous solutions, the formation of spherical micelle‐like aggregates has been observed in systems of amphiphilic block copolymers in water. The aggregates, often called micelles due to structural similarities with surfactant associates, are found to exist above the critical micelle concentration (cmc). The micellization of amphiphilic block copolymers has been investigated using a wide range of techniques, such as size‐exclusion chromatography (SEC), static and dynamic light scattering (SLS and DLS), small‐angle x‐ray scattering (SAXS), small‐angle neutron scattering (SANS), transmission electron microscopy (TEM), viscometry, and steady‐state fluorescence spectroscopy.The present lecture is a review of recent work in our laboratory concerning the micellization of ionic block copolymers. These high‐molecular‐weight amphiphiles may contain one or more of a variety of ionic blocks, such as poly(4‐vinylpyridinium alkyl halides), poly(metal acrylates), poly(metal methacrylates) and sulfonated polystyrene. In water, such polymers are referred to as block polyelectrolytes, as they combine the colloidal behavior of block copolymers with the long‐range electrostatic interactions of polyelectrolytes. Early work in this field has been reviewed by Selb and Gallot.1

Diblock Copolymers with a Charged Block in a Selective Solvent: Micellar Structure

The structure of the micelles formed by a diblock copolymer with one neutral and one polyelectrolyte block dissolved in highly selective aqueous solutions is studied by the scaling method. In this case an insoluble neutral block forms the core of the micelle, while the corona consists of stretched polyelectrolyte chains. It is taken into account that the corona region can partially lose some of the counterions which can go to the outer solution; therefore the corona is always slightly charged. In some regimes the corona consists of two layers: the inner layer with the concentration blob structure and the outer layer with the electrostatic blob structure. The diagram of states showing different regimes of behavior of the micelles is constructed.

Micellization in Block Polyelectrolyte Solutions. 2. Fluorescence Study of the Critical Micelle Concentration as a Function of Soluble Block Length and Salt Concentration

Critical micelle concentrations (cmcs) of block polyelectrolyte micelles formed from poly(styrene-b-sodium acrylate) in aqueous and NaCl salt solutions were investigated by fluorescence measurements of solubilized pyrene. The measurements were made for a range of PS block lengths (6 to 110 units) and of PANa block lengths (15-2400 units). For the series consisting of 11 and 23 units of PS, which had been prepared with a wide range of PANa lengths, the cmc was found to pass through a maximum as a function of the soluble (PANa) block length. It was observed that as the length of the PS block increased, the dependence of the log cmc versus the PANa block length decreased. For all samples except the PS(6) series at low salt concentrations, the log cmc values were found to decrease linearly as a function of the square root of the NaCl concentration (√C s ) which was varied from 0.10-2.5 M. The shape of the gradient d(log cmc)/d(√C s ) versus the log of the number of PANa units was found to follow a curve of the same shape for the block polyelectrolyte micelles consisting of 6, 11, and 23 units of PS. The behavior of the curve was explained on the basis of polyelectrolyte conformations.

Micellization in Block Polyelectrolyte Solutions. 3. Static Light Scattering Characterization

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMicellization in Block Polyelectrolyte Solutions. 3. Static Light Scattering CharacterizationKarine Khougaz, Irina Astafieva, and Adi EisenbergCite this: Macromolecules 1995, 28, 21, 7135–7147Publication Date (Print):October 1, 1995Publication History Published online1 May 2002Published inissue 1 October 1995https://doi.org/10.1021/ma00125a016RIGHTS & PERMISSIONSArticle Views657Altmetric-Citations127LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Polymers of 1‐azabicyclooctane[4,2,0]. Part 3. Modification of polystyrene‐block‐poly‐1‐azabicyclooctane[4,2,0

AbstractPolystyrene‐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 exhibit any surface activity. In a water/DMF (9/1) solution the polymers have a core‐shell micelle‐like structure of collapsed polystyrene block which is solubilized by the surrounding polyelectrolyte block.

Critical micellization phenomena in block polyelectrolyte solutions

Critical micelle concentrations (cmc's) were measured for a range of block copolyelectrolytes based on styrene (the insoluble block) and sodium acrylate. The lengths of the styrene blocks ranged from 6 to 110, while those of the polyelectrolyte ranged from ca. 300 to ca. 1400. cmc results were interpolated for a constant polyelectrolyte block length of 1000 units. It was found that changing the insoluble block length from 6 to 110 lowered the cmc from 1.6×10 -5 to 5×10 -8 M. By contrast, changing the soluble blocks length from 300 to 1400 typically changed the cmc values by less than a factor of 2

Self-assembly of block copolymers with a strongly charged and a hydrophobic block in a selective, polar solvent. Micelles and adsorbed layers

The aggregetion of diblock copolymers consisting of a neutral block (A) and a polyelectrolyte block (P) in aqueous salt solution, a precipitant for the A block, is examined using a scaling model. Two self-assembled structures ere discussed: micelles and adsorbed layers, as well as the equilibrium between them. The salt concentrations considered are moderately high, so that the electrostatic persistence length of the charged block is smaller than the range of excluded volume correlations. The aggregation number of micelles and the surface density adsorbed layers were found to increase, and the charged block thickness to decrease, with salt concentration

Interfacial behavior of block polyelectrolytes. 6. Properties of surface micelles as a function of R and X in P(S260-b-VP240/RX)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInterfacial behavior of block polyelectrolytes. 6. Properties of surface micelles as a function of R and X in P(S260-b-VP240/RX)J. Zhu, A. Eisenberg, and R. B. LennoxCite this: Macromolecules 1992, 25, 24, 6556–6562Publication Date (Print):November 1, 1992Publication History Published online1 May 2002Published inissue 1 November 1992https://doi.org/10.1021/ma00050a026RIGHTS & PERMISSIONSArticle Views178Altmetric-Citations48LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Interfacial behavior of block polyelectrolytes. 5. Effect of varying block lengths on the properties of surface micelles

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInterfacial behavior of block polyelectrolytes. 5. Effect of varying block lengths on the properties of surface micellesJ. Zhu, A. Eisenberg, and R. B. LennoxCite this: Macromolecules 1992, 25, 24, 6547–6555Publication Date (Print):November 1, 1992Publication History Published online1 May 2002Published inissue 1 November 1992https://doi.org/10.1021/ma00050a025RIGHTS & PERMISSIONSArticle Views486Altmetric-Citations113LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (4 MB) Get e-Alerts Get e-Alerts