Acidic poly-electrolytes

Gamble, D. S. (1970). Titration curves of fulvic acid The analytical chemistry of a weak acid poly electrolyte. Can. J. Chem. 48, 2662-2669. 

Cesarano J, Aksay lA, Bleier A (1988) Stability of aqueous alpha-Al203 suspensions with poly(methacrylic acid) poly-electrolyte. J Am Ceram Soc 71 250-255... 

Huang, Y, Yu, H., and Xiao, C. pH-sensitive cationic guar gum/poly (acrylic acid) poly electrolyte hydrogels Swelling and in vitro drug release. Carbohydr. Polym., 69, 774-783 (2007). 

Usually the acid-base properties of poly electrolyte are studied by potentiometric titrations. However it is well known, that understanding of polyelectrolyte properties in solution is based on the knowledge of the thermodynamic properties. Up to now, there is only a small number of microcalorimetry titrations of polyelectrolyte solutions published. Therefore we carried out potentiometric and microcalorimetric titrations of hydrochloric form of the linear and branched polyamines at 25°C and 65°C, to study the influence of the stmcture on the acid-base properties. 

The simple and clean polymerization of t-butyl methacrylate provides an opportunity to produce well defined, poly-electrolytes of uniform size, because this poly-ester, similarly to its Si(CH3)3 analogue i9), is readily hydrolysed by acids into polymethacry-lic acid. Furthermore, as pointed out by Muller 36), it becomes possible to produce... 

In solutions, the counterions of poly electrolytes are HjO (for the polyacids) and OH (for the polybases), cations such as K+ and Na, or anions such as Cl (for the polysalts). The addition of polyvalent counterions (such as Ca, Mg, Cu, AT ) produces ionic cross-linking interfering with solubility The polyelectrolyte precipitates and may be redissolved upon addition of a strong acid (such as HCl). This can be regarded as a special case of ion exchange. 

The process described is referred to as ion-exclusion as discussed by Asher and Simpson 9. The resins used are normal and the non-ionic molecules are assumed to be small enough to enter the pores. When large non-ionic molecules are involved, an alternative process called ion-retardation may be used, as discussed by Hatch et al. W]. This requires a special resin of an amphoteric type known as a snake cage poly electrolyte. The polyelectrolyte consists of a cross-linked polymer physically entrapping a tangle of linear polymers. For example, an anion exchange resin which is soaked in acrylic acid becomes entrapped when the acrylic acid is polymerised. The intricacy of the interweaving is such that counter-ions cannot be easily displaced by other counter-ions. On the other hand, ionic mobility within the resin maintains the electro-neutrality. The ionic molecule as a... 

MTX MCC mPEG MA NFX PEO PCS PECs PLA PBLA PLG PPO PEG PCL PBLG PBS PGA Methotrexate Crystalline cellulose Monomethoxypoly(ethylene glycol) Maleic acid Norfloxacin Polyethylene oxide) Photon correlation spectroscopy Poly(electrolyte complexes) Poly(L-lactic acid) Poly( 3-benzyl-L-aspartate) Poly (lactide- co -glycolide) Polypropylene oxide) Polyethylene glycol) Poly(e-caprolactone) Poly(y-benzyl-L-glutamate) Phosphate buffered saline Poly(glycolic acid)... 

We consider simple polyelectrolytes, which we define as homopolymers In which each monomer unit carries an ionizable group. Such a group may be a strong acid or base, in which case its charge is virtually independent of pH (strong poly electrolyte]. On the other hand, weak polyelectrolytes carry weakly acidic (for example carboxyl) or weakly basic (for example amino) groups their solution behaviour depends on pH. 

In order to describe the effect of ionic strength and pH, the electrost itic energies resulting from the oligoelectrolytic character of humic and fulvic acids (i.e., intermediate in character between simple ions and true poly electrolytes) must be assessed. The polyelectrolytic and oligoelectrolytic effect in proton and metal-ion binding has been well studied in physical biochemistry. 

Figure 9.33. (a) Schematic description of the effects of ionic strength (I) and pH on the conformations of a humic molecule in solution and at a surface. Rh denotes the hydrodynamic radius of the molecule in solution and 6h denotes the hydrodynamic thickness of the adsorbed anionic poly electrolyte. (Adapted from Yokoyama et al., 1989 and O Melia, 1991). (b) The influence of ionic strength of pH on diffusion coefficient, Dl, and on Stokes-Einstein radius of a humic acid fraction of 50,000-100,000 Dalton. (From Cornel et al., 1986). 

In the development of fuel-cell technology based on this unique polymer electrolyte, special chapters in electrochemical science and engineering have emerged, addressing the fuel-cell ionomeric membrane itself and the optimized fabrication of MEAs. The invention of Nafion, a poly(perfluorosulfonic acid) (poly(PFSA)) at DuPont in the 1960s, was, in fact, a key (if not the key) milestone in the development of PEFC technology. The chemical and mechanical properties of such poly(PFSA) extruded membranes, which are based on a perfluorocar-bon backbone, enabled to achieve stable materials properties and, consequently,... 

In the preceding section, the remarkable salt concentration effect on the acid dissociation equilibria of weak polyelectrolytes has been interpreted in a unified manner. In this treatment, the p/( ,pp values determined experimentally are believed to reflect directly the electrostatic and/or hydrophobic nature of polyelectrolyte solutions at a particular condition. It has been proposed that the nonideality term (Ap/Q corresponds to the activity ratio of H+ between the poly electrolyte phase and the bulk solution phase, and that the ion distribution equilibria between the two phases follow Donnan s law. In this section, the Gibbs-Donnan approach is extended to the equilibrium analysis of metal complexation of both weak acidic and weak basic polyelectrolytes, i.e., the ratio of the free metal ion activity or concentration in the vicinity of polyion molecules to that of bulk solution phase is expressed by the ApAT term. In Section III.A, a generalized analytical treatment of the equilibria based on the phase separation model is presented, which gives information on the intrinsic complexation equilibria at a molecular level. In Secs. B and C, which follow, two representative examples of the equilibrium analyses with weak acidic (PAA) and weak basic (PVIm) functionalities have been presented separately, in order to validate the present approach. The effect of polymer conformation on the apparent complexation equilibria has been described in Sec. III.D by exemplifying PMA. 

WM Anspach, JA Marinsky. Complexing of nickel(II) and cobalt(II) by a polymethacrylic acid gel and its linear poly electrolyte analog. J Phys Chem 79 433-439, 1975. 

Examination of the kq values listed in Table 2.2 clearly reveals the conformational transition of the poly electrolyte for example, PMAA has been labeled with 1-pyrene acrylic acid (PyAA) [22], ACE [12], 1VN [12], and vinyl diphenylanthracene (VyDPA) [94] and quenched with nitromethane in aqueous media. The kq values derived from lifetime data for each of these labels are of the order of 0.5 x 109 moE1 dm3 s 1 at low degrees of ionization. The formation of the hypercoiled conformation provides a degree of protection for the excited state from the quencher, and a low value of kq results. 

Okubo, T. and Ise, N. Synthetic Poly electrolytes as Models of Nucleic Acids and Esterases. 

Natural organic polyelectrolytes are some of the most active components of natural soil-water systems entering into physical and chemical reactions with practically all other components of the systems. Most pesticides are strongly sorbed by insoluble natural organic polyelectrolytes, such as humic acid. The soluble humic salts, however, may solubilize insoluble pesticides. Pesticides also enter into chemical reactions with natural organic poly electrolytes. The mechanisms of most of these interactions have not yet been elucidated. Elucidation will require isolation of well-defined, chemically and physically homogeneous natural polyelectrolyte fractions. 

In general, the properties of a biosystem and a synthetic polymer as well as the nature of the biological medium dictate the degree and type of interaction between a biostructure and a polymer. The biocompatibility of synthetic polymers depends on their chemical nature, physical state, and macroscopic form, which can be modified by functionalization of the polymer skeleton. Many biopolymers, such as proteins and nucleic acids, are natural poly electrolytes. Similarly, the outer cell membrane of living cells has charged groups. The biological medium is an electrolyte with an aqueous phase. Therefore, electrostatic... 

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