Polyampholytes

Synthetic examples include the poly(meth)acrylates used as flocculating agents for water purification. Biological examples are the proteins, nucleic acids, and pectins. Chemically modified biopolymers of this class are carboxymethyl cellulose and the lignin sulfonates. Polyelectrolytes with cationic and anionic substituents in the same macromolecule are called polyampholytes. 

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). 

Proteins that are polyampholytes, upon addition of electrolyte, first undergo some salting in up to a certain ionic strength, since electrostatic interactions between ions are shielded by the additional simple ions of both sign. Adding more salt will then cause salting out as the added ions compete for water that would otherwise solvate the protein. 

A foaming composition having a specific pH and containing an ionic surfactant and a polyampholytic polymer whose charge depends on the pH is circulated in a well. By varying the pH, it is possible to destabilize the foam in such a way as to more easily break the foam back at the surface and possibly to recycle the foaming solution [76]. 

A terpolymer from a family of intramolecular polymeric complexes (i.e., polyampholytes), which are terpolymers of acrylamide-methyl styrene sulfonate-methacrylamido propyltrimethylammonium chloride [106,1418], has been reported. 

D. G. Peiffer, R. M. Kowalik, and R. D. Lundberg. Drag reduction with novel hydrocarbon soluble polyampholytes. Patent US 4640945, 1987. 

Kudaibergennow, S.E. Recent Advances in Studying of Synthetic Polyampholytes in Solutions. Vol 144, pp. 115-198. 

Mdhwald, H., Menzel, H., Helm, C.A. and Stamm, M. Lipid and Polyampholyte Mono-layers to Study Polyelectrolyte Interactions and Structure at Interfaces. Vol. 165, pp. 151-175. 

Following similar reasoning, the adsorption pattern observed for ampholytic polyelectrolytes Ocan be explained. As illustrated in Fig. 4, polyampholytes show maximum adsorption around their isoelectric point (i.e., the pH where the net charge of the polyampholyte is zero). 

Fig. 4. Influence of pH on the plateau-value /T of adsorption isotherms of polyampholytes. At either side of the isoelectric point, i.e.p., the polyampholyte attains a net charge causing intra- and intermolecular electrostatic repulsion. As a result, the mass of adsorbed polyampholyte, that can be accommodated per unit area of the sorbent surface, decreases. Electrostatic interactions are suppressed by increasing ionic strength, yielding /T less sensitive to pH.

Polyammonium-containing ligands, 24 44 Polyammonium macropolycycles, 76 780 Polyampholytes, 20 475 479 solution properties of, 20 479 synthesis of, 20 477- 478 Poly(anhydrides), bioresorbable polymers, 3 740... 

Solution prepregging, 20 284-285 Solution processing, 14 80 Solution process, of ethylene-propylene polymer manufacture, 10 708-710 Solution properties of lignin, 15 13 of polyampholytes, 20 479 ofVDC copolymers, 25 703-706 Solution spectrophotometry, 9 232 Solution spinning... 

Early examples of micelles formed by BAC triblock copolymers have been reported by Patrickios and coworkers, who studied the formation of micelles from polyampholytic PDMAEMA-PMMA-PMAA and PDMAEMA-poly(2-phenylethylmethacrylate)-PMAA copolymers as a function of pH [285-287]. 

Polyampholytic micelles from PDMAI-PS-PMAA triblock copolymers were reported by Bieringer et al. [289]. Investigations on the pH-dependent... 

Investigation of Solution Behavior of Polyampholytes using Gradients. . 95... 

While the bulk behavior of polyampholytes has been investigated for some time now, studies of interfacial performance of polyampholytes are still in their infancy. There are several reasons for the limited amount of experimental work the major one being the rather complex behavior of polyampholytes at interfaces. This complexity stems from a large array of system parameters governing the interaction between the polymer and the substrate. Nearly all interfacial studies on polyampholytes reported to-date involved their adsorption on solid interfaces. For example, Jerome and Stamm and coworkers studied the adsorption of poly(methacryhc acid)-block-poly(dimethyl aminoethyl methacrylate) (PMAA-fc-PDMAEMA) from aqueous solution on sihcon substrates [102,103]. The researchers found that the amount of PMAA-fo-PDMAEMA adsorbed at the solution/substrate interface depended on the solution pH. Specifically, the adsorption increased... 

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