NaPAA, sodium

Sodium polyacrylate (NaPAA) [9003-04-7]. Commercial polyacrylamide was neutralised with an aqueous solution of NaOH and the polymer ppted with acetone. The ppte was redissolved in a small amount of water and freeze-dried. The polymer was repeatedly washed with EtOH and water to remove traces of low... 

The membrane performance was good, during almost 60-h operation and the permeate flux was stable after initial decline. The biggest flux decrease was observed when macromolecular sodium polyacrylate was introduced first after dosing 0.4 g/L of NaPAA, then after injection of the next portion (1 g/L NaPAA). In that time, permeate flux declined from 52 L/m h in the beginning (without the complexing agent), to 11 L/m h after injection of 1 g/L of the polymer. Further increase of polymer concentration did not result in the flux decline, as well as addition of CoCF suspension. 

The interpretation in terms of the dehydration turns out to be useful also for the deceleration effect by polyelectrolytes observed for the ammonium cyanate-urea conversion. In this case, AW was hardly affected by polyelectrolyte addition whereas AS was decreased. For example JH and AS" were 22.9 kcal mole and — 2 e.u. in the absence of polyelectrolytes. If sodium polyacrylate (NaPAA) was added at a concentration of 0.1 equiv 1 these parameters were 20.3 kcal mole and — 12e.u. [22]. ... 

Counterion condensation theory (CCT) predicts the concentration of bound counterions (1-5). However, traditional experim tal methods only measure the fraction of counterions bound and not their concentration within e condensed volume. The chemical trapping method provides this information (7-11). Here, we use chemical trapping to estimate e concentration of counterions in the condensed volume of an anionic polyelectrolyte, sodium polyaciylate, NaPAA and compare our result with that obtained from CCT. 

Chemical trapping with an arenediazonium ion provides the first experimental estimate of counterion concentration in the condensed volume around an anionic polyelectrolyte, NaPAA. The method can be applied to other polyelectrolyte systems. Inherent advantages of the method are the low selectivity of the probe towards a variety of nucleophiles and its insensitivity to medium effects such that product yields are almost directly proportional to nucleophile concentration. We are currendy using chemical trapping to estimate the concentration of condensed counterions around sodium polystyrene... 

We begin with early SAXS curves obtained for polyelectrolytes. In Fig. 2-1 are (Jotted SAXS data of (fractionated) sodium polyacrylate (NaPAA) [22,24]. 

Fig. 2-1. Scattering intensity (I) vs scattering vector (q) plots for sodium polyacrylate (NaPAA) solutions at 22 °C influence of degree of neutralization (a) at a weight-average degree of polymerization Pws= 1470 and [NaPAA] = 0.02gml" . Taken from [24] with the permission of the American Chemical Society...

First, discu on will be given on the systems water (component 1)-polyelectrolyte (component 2)-simple electrolyte (component 3) 16, 23). The mean activity coefficient of a sodium polyacrylate (d ee of neutralization, 0.98) (y ,8) at 25°C in the tem H20-NaPAA-NaClis given as a function of the polyelectrolyte concentration m at constant concentration of NaCl (wjg) in Fig. 5. Here it is to be noted that the y ,2 values were obtained by using a value of 0.6 as the degree of gegenion association, which was foimd from an independently carried out transference experiment (57). Clearly, the y ,2 depends very sharply on the concentrations of polyelectrolyte and simple electrol3 e. The mean activity confident of NaCl (y ,s) hr the ternary system HgO-NaPAA-NaCl presented in Fig. 6 shows less pronounced concentration dependence than the y ,a case. These remarkable concentration dependences can be conveniently expressed and discussed in terms of the following interaction parameters. Pfji... 

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