The influence of pH on the alternate multi-layered adsorption of macrocations and macroanions on colloidal spheres

The -potential and thickness of the alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres in suspension were measured at pH values ranging from 2.8 to 10.8 via electrophoretic light-scattering measurements. Colloidal silica spheres (110 nm in diameter) were used. The macrocations used were poly(4-vinyl-N-n-butyl pyridinium bromide) (C4PVP, a strongly basic macroion) and poly (allylamine) (PAL, which is weakly basic). Sodium poly(styrene sulfonate) (NaPSS, strongly acidic) and sodium polyacrylate (NaPAA, weakly acidic) were used as macroanions. The macrocations were added first in all of the experiments. The alternate adsorption of C4PVP and NaPSS takes place for a wide range of pH values, between 2.8 and 8.7. For C4PVP + NaPAA systems, alternate layers are formed only at neutral pH values and within three to six layers. Multiple adsorption phenomena are observed at acidic and neutral pH values for PAL + NaPSS and PAL + NaPAA systems, respectively. These results strongly support the theory that the synchronous delicate balancing of the electrostatic interactions among the macrocations, the macroanions, and the colloidal spheres is important for the alternate multiple adsorption.     

Synchronous alternate multilayered adsorption of poly(4-vinyl-N-n-butylpyridinium) cations and poly(styrene sulfonate) anions on polystyrene colloidal spheres

Alternate multiple adsorbed layers of up to six macrocations [poly(4-vinyl-N-n-butyl-pyridinium bromide)] and macroanions [sodium poly(styrene sulfonate)] are formed on monodispersed polystyrene colloidal spheres above the critical concentration of the macroions, m ^*. The m ^* value is the minimum number of macroions needed to reverse the sign of the ζ potential of the spheres in the first adsorption step. Alternate sign reversal in the ζ potential and expansive–contractive thickness changes are observed on the repeated and alternate addition of macrocations first and macroanions next. When the macroanions are added first, sign reversal in the ζ potential and reversible expansion and contraction do not occur. Breaking of the alternate multiple-type adsorption also occurs when equivalency in the number of dissociative groups of macrocations and macroanions is broken. Synchronous conformational changes of macrocations and macroanions in the multiple-adsorbed layers occurs only when the conformational rigidities with the multiple electrostatic and hydrophobic attraction and/or repulsion between macrocations and macroanions are delicately balanced. Received: 12 August 1999/Accepted in revised form: 18 November 1999     

Alternate multi-layered adsorption of macro-cations and -anions on the colloidal spheres. Influence of the deionization of the complexation mixtures with coexistence of the ion-exchange resins

The alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres, in which the complexation mixtures are deionized with ion-exchange resins are studied with help of the electrophoretic light-scattering, dynamic light-scattering and transmitted electron-microscopy techniques. The results are compared with those without resins. Colloidal silica spheres (110 nm in diameter) and monodispersed polystyrene spheres (220 nm) are used as colloidal spheres. The macrocations used are poly (4-vinyl-N-n-butyl pyridinium bromide) and poly (allylamine hydrochloride). Sodium poly (styrene sulfonate) and sodium polyacrylate are used as macroanions. The macroion-colloid complexations are formed firmly when the complexation suspensions are deionized with the resins.     

Alternate sign reversal in the ζ potential and synchronous expansion and contraction in the absorbed multi-layers of poly(4-vinyl-N-n-butylpyridinium bromide) cations and poly(styrene sulfonate) anions on colloidal silica spheres

Alternative multiple absorbed layers of up to ten macrocations [poly(4-vinyl-N-n-butylpyridinium bromide)] and macroanions [sodium poly(styrene sulfonate)] are formed on colloidal silica spheres above the critical concentration of macroions, m*. The m* value is the minimum number of macroions required to reverse the sign of the ζ potential of the spheres in the first absorption step. Alternative sign reversal in the ζ potential and expansive–contractive thickness changes are observed by the repeated and alternate addition of macrocations first and macroanions next. During multiple absorption, the pH and conductivity values decrease and increase continuously as the number of absorbed layers increases. When the macroanions are added first, sign reversal in the ζ potential and reversible expansion and contraction do not occur. Breaking of the alternate multiple-type absorption occurs when equivalency in the number of dissociative groups of macrocations and macroanions is broken. Synchronous conformational changes of macrocations and macroanions in the multiple- absorbed layers, where balancing of the conformational rigidities with the multiple electrostatic attraction and repulsion between macrocations and anions occurs, are supported strongly. Received: 12 January 1999 Accepted in revised form: 25 March 1999     

Multilayered adsorption of macrocations and macroanions on colloidal spheres as studied by dynamic light scattering measurements

The electrophoretic light scattering data on the thickness of the alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres, which have been published by the authors in Colloid and Polymer Science (1999) 277;813, (2000) 278:380 and (2002) 280:533, are reexamined with help of the dynamic light scattering measurements. Colloidal silica spheres (110 nm in diameter) and monodispersed polystyrene spheres (220 nm) are used as colloidal spheres. The macrocations used are poly(4-vinyl- N- n-butylpyridinium bromide and poly(allylamine). Sodium poly(styrene sulfonate) and sodium polyacrylate are used as macroanions. It was clarified in the previous work that a very small amount of the large aggregates of the macroions coexists for most of the suspensions and the thickness values reported are large compared with the true values. The corrected thickness values support the continuous thin layer's growing adsorption of the macroions on the colloidal surfaces but do not support the expansion–contraction-type adsorption.     

Polyelectrolyte effects on the charge transfer complex formation between FMN and indole derivatives

The complex formation of flavin mononucleotide (FMN) with tryptamine, indoleacetate, and trytophan was investigated in the presence of polyelectrolytes; that is, sodium polyethylene sulfonate (NaPES), sodium polystyrene sulfonate (NaPSS), and a copolymer of diethyldiallylammonium chloride and sulfur dioxide (DECS). The complexation of FMN and tryptamine was strongly retarded by the macrocations and macroanions, whereas that of FMN and indoleacetate was enhanced by the macrocations. Furthermore, the equilibrium constants of FMN-tryptophan complex were insensitive to the addition of polyelectrolytes. These results suggest that the complexation of FMN was strongly influenced by the electrostatic interactions between the reactant ions and macroions, in addition to those between the reactant ions, in conformity with the secondary salt effect.     

Complex formation of poly(4-vinyl-N-alkylpyridinium) salts or polymer containing flavin mononucleotide with indole derivatives

A charge-transfer-type complex formation between poly(4-vinyl-N-propylpyridinium bromide) (C3PVP), poly(4-vinyl-N-butylpyridinium bromide) (C4PVP) or poly(4-vinyl-N-benzylpyridinium chloride) (BzPVP), and indole derivatives or between polymer containing flavin mononucleotide residues and indole derivatives was studied in the presence of simple and polyelectrolytes. The association constant (K) of the complex formation with indole acetate increased in the order BzPVP > C4PVP > C3PVP, which indicated an important contribution by hydrophobic interaction. The addition of simple and polyelectrolytes decreased the association constants. This was explained by the “secondary salt effect” of the salts. The importance of the electrostatic interactions in the complexation systems was obvious. The influence of simple electrolytes on the K values was discussed theoretically according to Manning's theory.     

Catalytic effect of poly(4-vinyl-N-alkylpyridinium) salts on the hydrolysis of ester- and amide-containing indolyl groups

Alkaline hydrolyses of p-nitrophenyl-3-indoleacetate (p-NPIA) and N-(indole-3-acryloyl)imidazole (IAI) were studied in the presence of poly(4-vinyl-N-propylpyridinium bromide) (C3PVP), poly(4-vinyl-N-benzylpyridinium chloride) (BzPVP), and copolymers of 4-vinyl-N-benzylpyridinium chloride and 4-vinyl-N-cetylpyridinium bromide (C16BzPVP). The hydrolyses were enhanced by the addition of these cationic polyelectrolytes. The magnitudes of the enhancement were in the order C16BzPVP > BzPVP > C3PVP, which is explainable in terms of the hydrophobicity of the polymers. The result and activation parameters obtained indicated that the substrates bound to polymers were more reactive than free substrates. The association constants obtained from the kinetic measurements (K) increased in the order BzPVP < C3PVP < C16BzPVP, which may suggest an important contribution of charge transfer interaction, in addition to electrostatic and hydrophobic interactions, between the polymers and the substrates. The association constants between the polymers and IAI were also obtained independently from the spectrophotometric measurements (K^*) with the charge transfer absorption bands. The lack of a satisfactory agreement between K and K^* is discussed.     

Drying dissipative patterns of aqueous solutions of poly (4-vinyl-N-alkyl-pyridinium halide)

Drying dissipative structural patterns of aqueous solutions of poly (4-vinyl-N-alkyl-pyridinium halide) were studied on a cover glass. The broad rings were observed at the outside edge of the dried film. The broad ring size (or the area of the dried film, S) increased as polymer concentration increased. The broad ring size decreased and then turned to increase when the hydrophobicity of the polymers increased. The drying time from the initial liquid (T) was insensitive to the polymer concentration. But, T was sensitive to the kind of polymers, i.e., hydrophobicity of polycations, and roughly in the opposite order to that of S. Spoke-like macroscopic patterns appeared clearly for poly (4-vinyl-N-n-butylpyridinium bromide) (C4PVP), but were not observed clearly for the other polymers. Cross-like microscopic patterns appeared from which the polymers with the extended conformation are deduced to be crystallized during the course of dryness. The cooperative crystallization took place between the polymer and the salt in the C4PVP + KCl mixtures. When two different polymers were mixed, segregation and then independent crystallization of each single component polymers were observed. The dissipative effect is important for determining of the polymer crystal structure during the course of crystallization.     

Semi-Interpenetrating Hydrogels of Polyelectrolytes,Polymer-Metal Complexes and Polymer-Protected Palladium Nanoparticles

Summary: Semi-interpenetrating hydrogels (SIHs) of polyelectrolytes consisting of poly(acrylamide) hydrogel (PAAH) as matrix and sodium poly(styrenesulfonate) (NaPSS), poly(N,N′-dimethyl-N,N′-diallylammonium chloride) (PDMDAAC), stoichiometric interpolyelectrolyte complex of NaPSS-PDMDAAC, and linear polyethyleneimine-metal complexes (PMC) as well as polymer-protected palladium nanoparticles were prepared by in situ polymerization, e.g. crosslinked acrylamide chains were formed in aqueous solutions of NaPSS, PDMDAAC, NaPSS-PDMDAAC (1:1 mol/mol), PMC and palladium nanoparticles protected by poly(N-vinylpyrrolidone) (PVP), poly-(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), and linear poly(ethyleneimine) (LPEI) respectively in the presence of N,N′-methylenebisacrylamide. For each system the equilibrium swelling degree α and the parameters n and k describing the mechanism of water transport into SIHs volume was determined. Catalytic properties of SIHs were studied in allyl alcohol hydrogenation and cyclohexane oxidation reactions.     

Association of copolymers of methacrylic acid and 4-vinylpyridine in comparison with an intermacromolecular complex of poly(methacrylic acid) with poly(4-vinylpyridine)

Solution properties of copolymers [C(MA-Py)x] of methacrylic acid and 4-vinylpyridine and intermacromolecular complexes of poly(methacrylic acid) (PMAA) and poly(4-vinylpyridine) (PVP) in the presence or absence of a proton-accepting water-soluble polymer such as poly(ethylene glycol) (PEG) in water/methanol mixed solvent are studied by potentiometric titration, turbidity and viscosity methods. These copolymers behave like polyampholytes and their solubilities are strongly dependent with pH changes. The pH regions where they are precipitated around their isoelectric points are narrower than those of the intermacromolecular complex of PMAA with PVP. The polyampholyte can form an intermacromolecular complex with PEG in acidic solution but this complex is soluble in the medium.     

Spontaneous self-assembly of metal-organic cationic nanocages to form monodisperse hollow vesicles in dilute solutions

In this communication we report the unprecedented spontaneous self-assembly of cationic nanoporous metal-organic coordination cages (nanocages) into giant hollow vesicle-like structures in polar solvents. Such highly soluble nanocages (macrocations) have separated hydrophobic regions. However, their assembly is not due to hydrophobic interactions but the counterion-mediated attractions, very similar to the unique self-assembly of polyoxometalate macroanions into single-layer, spherical blackberry structures, as characterized by laser light scattering and TEM studies. This is the first study on the solution behavior of metal-organic nanocages and also the first report on the self-assembly of soluble macrocations. Therefore, the blackberry structure is likely to be a universal type of self-assembly for soluble macroions. In addition, the self-assembled nanocages can provide blackberry structures a wide range of organic functionalities that are impossible to reach with purely inorganic systems, which may open the door to many types of applications.     

Adsorption of sodium polyacrylate in high solids loading calcium carbonate slurries

The adsorption of sodium polyacrylate (NaPAA) in slurries with up to 75 wt.% calcium carbonate was investigated with the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and adsorption of probe molecules. Analysis of the IR spectra demonstrated that the carboxylate groups of NaPAA adsorbed onto ground calcium carbonate (GCC) in three different modes. These modes were shown to be dependent on the solids loading and age of the slurry. Further investigation lead to the determination of the chelating ability of NaPAA at high solids loading.     

Adsorption of linear and star-shaped polyelectrolytes to monolayers of charged amphiphiles

Adsorption of polyelectrolytes has been studied employing monolayers of ionic amphiphiles at the air water interface as model surfaces. The adsorption of polyelectrolytes from a solution brought into contact with the amphiphile monolayer results in changes of the monolayer structure and properties. Monitoring these changes can be done by recording the changes in surface pressure. The kinetics of the adsorption depends strongly on the nature of the polyelectrolyte. Depending on the structure of the polyelectrolyte a purely diffusion controlled adsorption or a sequence of diffusion controlled adsorption and ordering processes have been identified to determine the kinetics. The influence of the molecular architecture on the polyelectrolyte adsorption has been further studied employing linear and star shaped poly(acrylic acid) and poly(N-propyl-4-vinyl pyridinium bromides), respectively. An unexpected behavior with an induction period in the adsorption kinetics of both polymers has been found. Furthermore, the degree of branching has only very minor effects on the adsorption kinetics.     

Dielectric relaxations in a series of vinyl aromatic polymers: Poly(2-vinyl-N-ethylcarbazole), poly(3-vinyl-N-ethylcarbazole), poly(2-vinylanthracene), and poly(α-methyl-2-vinylanthracene)

Two dielectric relaxations have been studied on poly(2-vinyl-N-ethylcarbazole) (P2VK) and poly(3-vinyl-N-ethylcarbazole)(P3VK), poly(2-vinylanthracene) (P2VA) and poly(α-methyl-2-vinylanthracene) (PMe2VA). The relaxations in P2VK and P3VK occur in the temperature regions 220°C and ?150°C. Evidence for a third relaxation in both polymers at ca. 120°C has been found; and, for this reason, the relaxations studied (220°C and ?150°C) are labeled α and β, respectively, and have been attributed to T_g and carbazole rotational libration about the bond connecting the carbazole moiety to the polymer backbone. Additionally β (ca. 20°C) and γ(ca. ?150°C) relaxations in P2VA and MeP2VA have been observed and assigned, respectively, to wagging motion and rotational libration of the pendant anthracene moiety.     

Effect of sodium poly(styrene sulfonate) on thermoreversible gelation of gelatin

The effect of an added polyanion, sodium poly(styrene sulfonate) (NaPSS), on the thermoreversible gelation and remelting of gelatin gels has been investigated by polarimetry and rheology. The presence of NaPSS can either enhance or reduce collagenlike helix formation, depending on the polymer concentration relative to that of gelatin and the gelation temperature. At temperatures < 20°C, the helical content is reduced by increasing the amount of added NaPSS, demonstrating the disruption of helical structure of gelatin by the polyanion. Synchronous measurements of optical rotation and modulus at 25°C, in both gelation and remelting, indicate that the optical rotation at the gel point for the pure gelatin is lowered on addition of NaPSS. At low frequency, the storage modulus of gelatin is increased by the addition of a small amount of NaPSS relative to that of gelatin, but decreased with excess NaPSS. The mechanical properties of gelatin with and without NaPSS will be discussed in light of the competition between network junction formation by strands of triple helices among gelatin chains and temporary ionic crosslinking between gelatin and the polyanion. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2287–2295, 1999     

Mesoscale assembly of NiO nanosheets into spheres

NiO solid/hollow spheres with diameters about 100 nm have been successfully synthesized through thermal decomposition of nickel acetate in ethylene glycol at 200 °C. These spheres are composed of nanosheets about 3-5 nm thick. Introducing poly(vinyl pyrrolidone) (PVP) surfactant to reaction system can effectively control the products’ morphology. By adjusting the quantity of PVP, we accomplish surface areas-tunable NiO assembled spheres from ∼70 to ∼200 m² g⁻¹. Electrochemical tests show that NiO hollow spheres deliver a large discharge capacity of 823 mA h g⁻¹. Furthermore, these hollow spheres also display a slow capacity-fading rate. A series of contrastive experiments demonstrate that the surface area of NiO assembled spheres has a noticeable influence on their discharge capacity.     

Capsules with Silver Nanoparticle Enrichment Subdomains and Their Antimicrobial Properties

The fabrication of polyelectrolyte multilayer capsules with controllable submicron‐sized subdomains and the in situ synthesis of silver nanoparticles are reported. Because poly(acrylic acid) (PAA) is released from the shell of the capsules in the dissolution process of sacrificial cores, the remaining poly(4‐vinylpyridine) (PVP) forms subdomains of spheres with controllable sizes, which can be tuned by the number of PVP/PAA bilayers. This creates capsules with special surface morphology and enables the in situ synthesis of Ag nanoparticles within the PVP subdomains on the shell of capsules. In addition, the in‐situ formed Ag nanoparticles can be mostly released from PVP subdomains of capsules in pH 2.0 solution, whereas they are stable in neutral solution. These specially designed capsules containing Ag nanoparticles can be used as antimicrobial materials and potentially benefit remote drug release by laser activation.     

Electrodeposition of Film-Forming Macroions

Ionizable film-forming macromolecules (RCOOH, RNH2, etc.) have recently found large-scale application as electrodepositable paints. Using bases or acids as solubilizers, macroanions (RCOO^?) or macrocations (RNH₃ are deposited from aqueous dispersions on the anode or cathode, respectively.

The electric current deposits the paint solids practically free from volatile organics on the outer and inner surfaces of merchandise, resulting in higher corrosion protection at substantially lower cost. Bath droplets adhering to freshly electrocoated objects are rinsed back into the bath by a process involving ultrafiltration. Thus electrocoating is one of the ecologically and commercially most viable paint processes.     

Surface-enhanced raman scattering from poly(4-vinyl pyridine)

Surface-enhanced Raman scattering (SERS) has been observed for poly(4-vinyl pyridine) absorbed onto silver island films. Bands near 1219 and 1613 cm^?1, which are weak in normal Raman spectra of PVP, are strong in SERS spectra, and the band near 1020 cm^?1, which is the strongest band in the normal spectra, is relatively weak in SERS. The strongest bands in the SERS spectra all belong to the same symmetry species as α_ZZ, implying that the pyridine moieties are adsorbed through the nitrogen atoms with a vertical conformation. The ring breathing mode of the pyridine rings is observed near 1020 cm^?1, a frequency characteristic of pyridinium ions or coordinated pyridine, providing further evidence for adsorption through the nitrogen atoms. Silver catalyzed photooxidation, which can lead to the appearance of artifacts in SERS spectra, particularly of polymers, can be reduced by overcoating SERS samples with thin films of polymers such as poly(methyl methacrylate) that have low Raman scattering cross sections.