Polyacrylic acid, determination

The molecular weight of the grafted chain of polyacrylic acid, determined by acid hydrolysis, is of the order of 10000. The product differs markedly from the original polyamide in electrochemical properties. As a confirmation of a radical mechanism, radical acceptors prevented the reaction (see Fig. 5). The possibility of a minor and competitive ionic mechanism was also considered. 

In the same year, Fulda and Tieke [75] reported on Langmuir films of monodisperse, 0.5-pm spherical polymer particles with hydrophobic polystyrene cores and hydrophilic shells containing polyacrylic acid or polyacrylamide. Measurement of ir-A curves and scanning electron microscopy (SEM) were used to determine the structure of the monolayers. In subsequent work, Fulda et al. [76] studied a variety of particles with different hydrophilic shells for their ability to form Langmuir films. Fulda and Tieke [77] investigated the influence of subphase conditions (pH, ionic strength) on monolayer formation of cationic and anionic particles as well as the structure of films made from bidisperse mixtures of anionic latex particles. 

The proposed mechanism of effect of surfactant and ultrasound is reported in Fig. 7.5. The long chain surfactant molecules attach to surface of nanoparticles due to physical adsorption. Only thin layer is adsorbed onto the CaC03 nanoparticles. Due to presence of ultrasound and use of surfactant will control the nucleation. Surfactant keeps the particles away from each other by preventing flocculation due to change in surface tension of reaction mass. The concentration of additives was changed from 0.2 to 1.0 g/L. Addition of 0.2 g/L tripolyphosphate shows the increase in the rate of precipitation which is determined from the Ca(OH)2 consumption. Polyacrylic acid shows the least rate of precipitation (0.115 mol/1), which... 

Flocculation is indeed dependent on polymer adsorption, and there are hypotheses correlating the two phenomena, but often these have been put forth without detailed measurement of the two phenomena simultaneously (10-13). In this paper, flocculation is investigated as a function of polymer and solution properties and hydrodynamic conditions by measuring different properties of the system, including adsorption, using well characterized kaolinite and polymer samples prepared specifically for this purpose. Also, the role of concentration and charge density of polyacrylamide and polyacrylamide-polyacrylic acid co-polymers in determining kaolinite flocculation is examined under controlled hydrodynamic conditions. 

Strong evidence of ionic association was found by Stilbs and Lindman 69) in their PGSE study of aqueous polyelectrolyte solutions, polyacrylic acid and poly-methacrylic acid, neutralized by tetramethylammonium hydroxide, with or without sodium counterions. While polymer diffusion could not be detected since its T2 was too short, TMAOH and water diffusion was measured as function of degree of neutralization a, or Na+ content. A pronounced minimum of D(TMAOH) near a = 1 was interpreted in terms of a two-site model, leading to the determination that at a = 1, approximately half of the counterions are bound in both systems. Fourier transform techniques permitted the simultaneous measurement of diffusion of water and TMAOH. 

IV Particle Size, The modal diameters of latices were determined by measuring the diameters of particles on electron micrograph negatives obtained by conventional procedures. In order to determine the mean, and the standard deviation from the mean, between 200 - 300 particles were measured. Latices prepared from polyacrylic acid in the manner described above were found to have coefficients of variation of <10% in all cases and sometimes <5%. Errors in particle size were estimated to be 10%. 

The present review deals mainly with two examples of polyelectrolyte phase behavior as discussed above. As an example for an H-type precipitation, the solution properties of polyvinylpyridinium chains are monitored as function of added inert salt. Here, we focus on the determination of the effective charge density and of the solvent quality parameter which are supposed to play a central role for the understanding of polyelectrolyte solution without specific counterion interactions. The second system under investigation comprises the interaction of polyacrylic acid with alkaline earth cations which exhibit very specific interactions, thus representing an example for type L-precipitation. Here the coil dimensions close to the phase boundary are compared to those close to type H-precipitation with inert added salt. 

The use of imprinted polymer ion separation and photometric detection has been demonstrated for Pb [19] and for U02 [35]. In the case of Pb ", the imprinted Pb " resin described above was packed into columns and used to remove Pb " from tap and seawater at a variety of pH values [8], The extraction efficiency of the imprinted resin was compared to the efficiency of an imidodiacetate resin (Chelex-100), a thiol-functionalised resin (Duolite G-73) and a high-capacity polyacrylic acid/polyvinyl alcohol resin (a proprietary NASA resin). The imprinted polymer s extraction efficiency was equal or better than the other resins and the effluents from the imprinted polymer resin were shown to be virtually free of contamination by other metal ions (Fig. 19.13). The purity of the effluent allowed the determination of Pb using a very non-specific colorimetric reagent, dithizone. The method is suitable for automation as an FIA technique. 

Potentiometric titration of pol3dtaconic acid, even in the presence of sodium chloride, does not result in curves with well-defined inflection points, such as those found in polyacrylic acid titrations, which allow simple determination of the acid content. Fig. 5 and 6. The shape of the... 

The mechanical properties of the surface-modified products were examined by a special shear test. After reactive surface modification under optimised chemical and technological conditions, the test specimens were cut and the pieces were bonded by special adhesives. The coimected pieces were examined in a shear test and the shear strength was determined in dependence on the chemical and processing conditions. The best results for polyamides were obtained for polyacrylic acid as the modifier with an increase of the shear strength from 28 MPa (non-modified polyamide) up to 37 MPa for polyacrylic acid-modified polyamide surfaces. 

The system resulting from mixing of aluminum oxide and polyacrylic acid in aqueous solution was determined to be very complex due to the partial dissolution of the oxide which liberates 10 4 mol/L multivalent aluminum ions in the supernatant at pH 5.0 [79], Definitely to set the chemical composition of the system, the aluminum ion concentration was fixed by dissolving the required amount of A1C13 in 10 3 mol/L KC1 at pH 4.06. Addition... 

Aggregation and fragmentation of colloidal particles has been investigated further employing natural polyelectrolytes like humic substances. Adsorption of humic acids on aluminum oxide was determined to resemble interfacial deposition on the basis of methods previously employed for the aluminum oxide/polyacrylic acid system [88]. Complexation by soluble aluminum ions produces pH drops that are very similar to that determined for polyacrylic acid, and essentially humic acids were determined to exert effects on the stability of colloidal aluminum oxide particles at pH 5 that are very similar to polyacrylic acid. 

The first of our preliminary results we demonstrate here is mass sensitivity. To do this we use a polyelectrolyte multilayer layer-by-layer deposition technique. Briefly, multilayers of polyethyleneimine and polyacrylic acid were deposited on the glutaraldehyde functionalized NOSA device, and on similarly functionalized silicon wafers in parallel. After deposition of each layer, output spectra were recorded to quantify shift in resonant wavelengths and polyelectrolyte multilayer film thickness was determined on silicon wafers using ellipsometry. Output spectra were compared to the initial baseline spectra to determine resonance shift (AA, in mn), and were plotted against film thickness as shown in Fig. 2. 

The concentration profiles show the distance to which polyacrylic acid penetrated the different samples. At the top of each curve there are figures which correspond to the volume fraction of the grafted polyacid in the dry membranes determined independently by a weighing technique. In calculations of the volume fractions of grafted polyacid, the density of PP was assumed to be equal to 0.898 g/cm and that of PAA 1.441 g/cm. ... 

Fig. 1. Concentration profiles of polyacrylic acid in two-component PP-g-PAA membranes determined by photometration. Light absorption expressed in relative units...

---