Solutions and Polyelectrolytes

The ratio of the radii of gyration of a cyclic polymer to that of a linear chain of the same molecular weight has been calculated theoretically and is expected to be (2) for dilute solutions of infinite chains. The ratio was found to be (1.9) for polymethylsiloxane dissolved in deuteriated benzene.  

Studies have been carried out on multi-component systems such as water— toluene-propan-2-ol, containing copolymers of (a) polyethylene oxide (PEO) and poly(2-vinylpyridine) (PVP) and (b) PEO and polystyrene (PS). In both cases the molecules were found to aggregate into micelles with the PEO blocks on the outside. 

Sulphonated polystyrene polyelectrolyte in both the add and the salt forms has been studied by neutron scattering. By selective labelling of the chains, it was found that the broad peak in the scattering signal arose from only the interchain component and was therefore due to interchain repulsion. The peak of this maximum, was proportional to the square root of the polymer concentration  

9m This agrees with two theoretical models either aligned rigid rods or a Gaussian succession of rigid segments.  

The radius of gyration of the add form was found to be similar to that of the untreated polystyrene, but the of the salt form was greater than that of the add and increased with salt concentration. The increase in implied that the salt groups associated into clusters, distribution of cluster sizes was expected to be large, with an appreciable number of isolated ion pairs. The polyelectrolytic copolymer of styrene and methacrylic acid was found to cluster in the add form at high polymer concentrations, and R was found to decrease with increasing polymer concentrations in both the add and salt forms.  

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With regard to counterion binding, some similarities are also observed between ionomer nonaqueous solution and polyelectrolyte aqueous solution. This is the short-range effect due to partial desolvation associated with coun-... 

To retain continuity with the earlier report, this review will be split into five sections Amorphous and Molten Polymers, Semi-crystalline Polymers, Solutions and Polyelectrolytes, Biological Materials, and Dynamical Studies of Macromolecules. 

The linearized Poisson-Boltzmann equation is referred to as the Debye-Hiickel equation. The constant coefficient appearing in the above equation is one of the important parameters in the discussion of electrolyte solutions and polyelectrolytes. We shall describe its physical interpretation and experimental relevance below and in Section 3.1.3.1. 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

The preparation of molecular composites by electropolymeriza tion of heterocycles in solution with polyelectrolytes is an extremely versatile technique, and many polyelectrolyte systems have been studied. The advantages of this method include the use of aqueous systems for the polymerization. Also, the physical and mechanical properties of the overall composite depend on the properties of the polyelectrolyte, so material tailorabiUty is feasible by selection of a polyelectrolyte with desirable properties. 

The structures of these ylide polymers were determined and confirmed by IR and NMR spectra. These were the first stable sulfonium ylide polymers reported in the literature. They are very important for such industrial uses as ion-exchange resins, polymer supports, peptide synthesis, polymeric reagent, and polyelectrolytes. Also in 1977, Hass and Moreau [60] found that when poly(4-vinylpyridine) was quaternized with bromomalonamide, two polymeric quaternary salts resulted. These polyelectrolyte products were subjected to thermal decyana-tion at 7200°C to give isocyanic acid or its isomer, cyanic acid. The addition of base to the solution of polyelectro-lyte in water gave a yellow polymeric ylide. 

Since the compartmentalization occurs as a result of microphase separation of an amphiphilic polyelectrolyte in aqueous solution, an aqueous system is the only possible object of study. This limitation is a disadvantage from a practical point of view. Our recent studies, however, have shown that this disadvantage can be overcome with a molecular composite of an amphiphilic polyelectrolyte with a surfactant molecule [129], This composite was dissolvable in organic solvents and dopable in polymer film, and the microphase structure was found to remain unchaged in the composite. This finding is important, because it has made it possible to extend the study on photo-systems involving the chromophore compartmentalization to organic solutions and polymer solid systems. 

Ise, N. The Mean Activity Coefficient of Polyelectrolytes in Aqueous Solutions and Its Related Properties. Vol. 7, pp. 536—593. 

For the preparation of spray-dried polyelectrolyte complexes, the polyanion was dissolved in dilute NH4HCO3 solution and mixed with the chitosan carbamate solution just before spray-drying. The excess NH4HCO3 decomposed thermally between 60 and 107 °C on the other hand, the carbamate function released carbon dioxide under the effect of the temperature at which the spray-drier was operated, thus regenerating chitosan at the moment of the polyelectrolyte microsphere formation (Fig. 5). 

The increasing dilution of flexible polyelectrolytes at low ionic strength, the reduced viscosity may increase first, reach a maximum, and then decrease. Since a similar behavior can also be observed even for solutions of polyelectrolyte lattices at low salt concentration, the primary electroviscous effect was thought as a possible explanation for the maximum, as opposed to conformation change. 

Our observation should be important in understanding these properties of polyelectrolytes in solutions and perhaps in gels. 

One of the main characteristic of polyelectrolyte is the pK of the - COOH function as usually with polyelectrolyte only the intrinsic pK (pKo) extrapolated to zero charge characterizes the polymer [41] one gets 3.30 which is in same range as other carboxylic polymers the apparent values of pK (pKa) depends on the charge distribution, on the polymer concentration, on the ionic strength of the solution and on the nature of the counterions. 

Harris, F. E. Rice, S. A. (1957). A model for ion binding and exchange in polyelectrolyte solutions and gels. Journal of Physical Chemistry, 58, 725-32. 

The polyelectrolyte cements are modern materials that have adhesive properties and are formed by the cement-forming reaction between a poly(alkenoic acid), typically poly(acrylic acid), PAA, in concentrated aqueous solution, and a cation-releasing base. The base may be a metal oxide, in particular zinc oxide, a silicate mineral or an aluminosilicate glass. The presence of a polyacid in these cements gives them the valuable property of adhesion. The structures of some poly(alkenoic acid)s are shown in Figure 5.1. 

Solutions of polyelectrolytes contain polyions and the free (individual) counterions. The dissociation of a polyacid or its salt yields polyanions, and that of a polybase or its salt yields polycations, in addition to the simple counterions. The polyampholytes are amphoteric their dissociation yields polyions that have anionic and cationic functions in the same ion and often are called zwitterions (as in the case of amino acids having HjN and COO groups in the same molecule). Such an amphoter will behave as a base toward a stronger acid and as an acid toward a stronger base its solution properties (particularly its effective charge) will be pH dependent, and an isoelectric point (pH value) exists where anionic and cationic dissociation is balanced so that the polyion s charges add up to zero net charge (and solubility is minimal). 

Matsuoka, H. and Ise> N. Small-Angle and Ultra-Small Angle Scattering Study of the Ordered Structure in Polyelectrolyte Solutions and Colloidal Dispersions. VoL 114, pp. 187-232. 

Systems that develop contractile forces are very intriguing as analogues of physiological muscles. The idea for gel muscles was based upon the work of Katchalsky and Kuhn. They have prepared polyelectrolyte films or fibers which become elongated or contracted in response to a change in pH of the surrounding solution, and have estimated the induced force and response time. The contraction of gel fibers is also achieved by electric fields. Use of electric fields has the merit that the signals are easily controlled. 

Polymer complexes associated with two or more complementary polymers are widely used in potential applications in the form of particles, hydrogels, films, and membranes. In particular, a polyion complex (PIC) can be easily formed when oppositely charged polyelectrolytes are mixed in aqueous solution and interact via... 

Recently the wall-PRISM theory has been used to investigate the forces between hydrophobic surfaces immersed in polyelectrolyte solutions [98], Polyelectrolyte solutions display strong peaks at low wavevectors in the static structure factor, which is a manifestation of liquid-like order on long lengths-cales. Consequently, the force between surfaces confining polyelectrolyte solutions is an oscillatory function of their separation. The wall-PRISM theory predicts oscillatory forces in salt-free solutions with a period of oscillation that scales with concentration as p 1/3 and p 1/2 in dilute and semidilute solutions, respectively. This behavior is explained in terms of liquid-like ordering in the bulk solution which results in liquid-like layering when the solution is confined between surfaces. In the presence of added salt the theory predicts the possibility of a predominantly attractive force under some conditions. These predictions are in accord with available experiments [99,100]. 

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