Polyelectrolyte behavior in solution

Soutar I, Swanson L (1994) Luminescence studies of polyelectrolyte behavior in solution. 3. Time-resolved fluorescence anisotropy measurements of the conformational behavior of poly(methacrylic acid) in dilute aqueous-solutions. Macromolecules 27(15) 4304-4311. doi 10.1021/ma00093a035... 

Addition of polymers can both stabilize and destabilize a solution. If the polymer contains ionizable units it is usually referred to as a polyelectrolyte. In this report we will focus on the effect from polyelectrolytes on the colloidal stability. In high dielectric media like water, where the monomers are ionized, the behavior of a polyelectrolyte is mainly governed by electrostatics and the connectivity of the monomers. Therefore, in theoretical studies, many important features of the polyelectrolyte behavior in water solution can be studied by a schematic description of the polyelectrolyte as a linear chain of charged monomers connected with springs. The bonding interaction between two monomers is Ub=K(r —a)2, where K is the spring constant, a is the equilibrium value and r is the distance between the two monomers (see Fig. 11). 

The properties of ionomer solutions are sensitive to not only the degree of the ionic functionality and the polymer concentration, hut perhaps even to a greater extent, the ability of the solvent to ionize the ion-pairs (64). Thus, non-ionizing solvents, usually those with relatively low dielectric constant, favor association of the ionic groups even in dilute solutions. In contrast, ionomer solutions may exhibit polyelectrolyte behavior in polar solvents due to solvation of the ion-pair that leaves the hound ions unshielded. 

The last chapter, written by S. E. Harding (Nottingham, United Kingdom), describes and discusses the macrostructure of mucus glycoproteins, complex polyelectrolytes whose behavior in solution is governed by aspects of secondary and tertiary stmcture that control their interactions in biological systems. 

We have initiated a series of investigations to study the catalytic effects of a class of cationic polyelectrolytes ranging in solution behavior from "normal" polyions to polysoaps upon the alkaline hydrolysis of neutral and anionic phenyl esters of varying chain lengths. Employing these catalysts of varying hydrophylic-hydrophobic character in reactions of neutral and anionic substrates of varied hydrophilic-hydrophobic character, it should be possible to elucidate the contributions of both the hydrophobic interactions and electrostatic interactions on the rate of reaction. 

Studies on the dilute solution behavior of sulfonated ionomers have shown these polymers to exhibit unusual viscosity behavior in solvents of low polarity. These results have been interpreted as arising from strong ion pair associations in low polarity diluents. Solvents of higher polarity, such as dimethyl sulfoxide and dimethyl formamide induce classic polyelectrolyte behavior in sulfonate ionomers even at very low sulfonate levels. To a first approximation these two behaviors, ion pair interactions or polyelectrolyte behavior, are a consequence of solvent polarity. Intramolecular association of Lightly Sulfonated Polystyrene (S-PS) results in a reduced viscosity for the ionomer less than that of polystyrene precursor at low polymer levels. Inter-association enhances the reduced viscosity of the ionomer at higher polymer concentrations. Isolation of the intra- and inter-associated species of S-PS has been attempted (via freeze drying). A comparison of selected properties reveals significant differences for these two conformations. 

Large polyelectrolytes, such as nucleic acids, and polyampholytes, such as proteins, are classified together as macroions. The electrostatic forces of attraction or repulsion between such charged particles play a major role in determining their behavior in solution. 

The presence of only a very small number of ionic groups can confer polyelectrolyte behavior on a macromolecule. Thus, potato amylopectin, which contains about 0.07% of phosphorus, corresponding to one ester phosphate group for every 200 n-glucose residues, exhibits polyelectrolyte behavior. In going from pure water to O.lM sodium chloride solution, [ij] decreases approximately fourfold and So increases by a factor of two. ... 

Both forces act into opposite directions the osmotic force tries to stretch the chain into the continuous phase, whereas the elastic force pulls the chain back to the interface. Setting Pci = Posm shows that AP a This is a much lower electrolyte dependence than in the case of low-molecular-weight ionic stabilizers where an exponential dependence of Vim is predicted (cf. equations (8.20)). Note, this scaling behavior of AR with Cl is the same as for polyelectrolyte chains in solution [2]. Regarding colloid stability, this means that polyelectrolyte-decorated droplets/particles possess an extraordinary electrolyte stability when compared to low-molecular-weight ionic stabilizers. Indeed, the Pincus brush behaviour (AP oc was experimen-... 

Attempts to quantitatively determine the extent of ionic dissociation of all relevant species including macroradicals and polymer molecules and to correlate such speciation with the variations observed for kp is difficult, if not impossible, in view of the complex acid-base properties and polyelectrolyte behavior as well as the coupled electrochemical equilibria. Studies into polyelectrolyte behavior in aqueous solution carried out so far, have been performed at conditions precisely defined with respect to solvent composition, ionic strength, concentration regime, and molecular weight. These conditions differ from the ones met in the actual free-radical polymerization experiments presented in Figure 3 and in Reference Despite this complexity, it has been reaUzed that with... 

Therefore, ionomer solutions cannot be treated as a whole and cannot even be divided into only two different problems the ionomer (or associating) behavior in nonpolar solvents and the polyelectrolyte behavior in polar solvents. A new structural problem will probably arise with most of the ionomers even if some of the solution properties appear to be similar. A lot of structural studies including small angle scattering and electron microscopy experiments will be necessary to understand the structure of ionomer solutions and such studies will be very helpful to understand the structure-properties relationships of ionic polymers. 

The viscosities were measured with an Ubbelohde Cannon 75-L, 655 viscometer. Formic acid was chosen as the solvent for the viscosity measurement because the polymer (VII) showed very low or no solubility in other common solvents. In a salt free solution, a plot of the reduced viscosity against the concentration of the polymer showed polyelectrolytic behavior, that is, the reduced viscosity ri sp/c increased with dilution (Figure 4). This plot passed through a maximum at 0.25 g/dL indicating that the expansion of the polyions reached an upper limit, and the effects observed on further dilution merely reflected the decreasing interference between the expanded polyions. 

In this article I review some of the simulation work addressed specifically to branched polymers. The brushes will be described here in terms of their common characteristics with those of individual branched chains. Therefore, other aspects that do not correlate easily with these characteristics will be omitted. Explicitly, there will be no mention of adsorption kinetics, absorbing or laterally inhomogeneous surfaces, polyelectrolyte brushes, or brushes under the effect of a shear. With the purpose of giving a comprehensive description of these applications, Sect. 2 includes a summary of the theoretical background, including the approximations employed to treat the equifibrium structure of the chains as well as their hydrodynamic behavior in dilute solution and their dynamics. In Sect. 3, the different numerical simulation methods that are appHcable to branched polymer systems are specified, in relation to the problems sketched in Sect. 2. Finally, in Sect. 4, the appHcations of these methods to the different types of branched structures are given in detail. 

More than half a century ago, Bawden and Pirie [77] found that aqueous solutions of tobacco mosaic virus (TMV), a charged rodlike virus, formed a liquid crystal phase at as very low a concentration as 2%. To explain such remarkable liquid crystallinity was one of the central themes in the famous 1949 paper of Onsager [2], However, systematic experimental studies on the phase behavior in stiff polyelectrolyte solutions have begun only recently. At present, phase equilibrium data on aqueous solutions qualified for quantitative discussion are available for four stiff polyelectrolytes, TMV, DNA, xanthan (a double helical polysaccharide), and fd-virus. 

The effectiveness of a polymeric flow enhancer is influenced decisively by the state of solution and the solvation characteristics. In the case of polyelectrolytes, in particular, the chemical nature plays a significant role, e.g., it was found for poly(acrylamide)-coacrylate that a significant increase in effectiveness arises with the increasing number of ionic groups. It is therefore necessary to consider, for example, such factors as the question of critical concentration, polymer-polymer and polymer-solvent interactions, the thermodynamic quality of the solvent, the proportion of ionic molecular groups and their behavior in the presence of lower-molecular-weight charge carriers. 

The nature of the viscosity determinations is illustrated in Figure 2. The upper curve shows the typical polyelectrolyte effect found for many of the resins in DMF. Adding CaCl2 to the DMF causes a saturation of charge and induces a relaxation of the resin structure, resulting in normal viscosity behavior. In the NaOH solution the resins acted normally. The... 

If we take into consideration that the lowest experimentally possible polyelectrolyte concentration cp is approximately 10 6 monomol L 1, it follows from Table 8 that the diluted solution state, cp 2000, i.e. if Mn >320,000 g-mol The theoretical treatment and the experimental studies of the concentration dependent behavior of polyelectrolytes in solution is usually restricted to the case with or without an excess of a low molecular electrolyte. A relatively limited amount of data exist for similar concentrations of polyelectrolytes and low molecular mass salt [97]. 

Adsorption of block copolymers onto a surface is another pathway for surface functionalization. Block copolymers in solution of selective solvent afford the possibility to both self-assemble and adsorb onto a surface. The adsorption behavior is governed mostly by the interaction between the polymers and the solvent, but also by the size and the conformation of the polymer chains and by the interfacial contact energy of the polymer chains with the substrate [115-119], Indeed, in a selective solvent, one of the blocks is in a good solvent it swells and does not adsorb to the surface while the other block, which is in a poor solvent, will adsorb strongly to the surface to minimize its contact with the solvent. There have been a considerable number of studies dedicated to the adsorption of block copolymers to flat or curved surfaces, including adsorption of poly(/cr/-butylstyrcnc)-ft/od -sodium poly(styrenesulfonate) onto silica surfaces [120], polystyrene-Woc -poly(acrylic acid) onto weak polyelectrolyte multilayer surfaces [121], polyethylene-Wocfc-poly(ethylene oxide) on alkanethiol-patterned gold surfaces [122], or poly(ethylene oxide)-Woc -poly(lactide) onto colloidal polystyrene particles [123],... 

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