Coagulation kinetics experiment

This experiment is significant because it shows that there is a maximum deposition density that can be achieved. This maximum could not be reached in the kinetics experiment because of the very long time period that would be required and in the pH experiment at pH below 3 the DNA-SWCNTs coagulate. Thus, increasing the salt concentration provides a simple way of maximizing deposition density, while still producing aligned DNA-SWCNTs. 

Further colloid/surfiice chemistry experiments references coagulation kinetics using Agl hydrosol (y.CAem. diSchulze/Hardy rule using Au hydrosol (ibid. 71(1994)624) determination of critical micelle concentration of surfactants using a colorimetric method ri hid.70(1993)254) density gradient columns displaying acid/base and metal ion (V, Cr, Fe, Co, Ni) equilibria (76iV 63(1986)148). 

The DLVO theoiy thus enabled theoretical significance to be given to the valence sequence in coagulation experiments that bad been observed many years earher by Schulze (1882) and Hardy (1900). Although expre ions of this type are useful in a qualitative predictive sense, the implication that there is a simple rule applicable to alt systems must be treated with considerable caution. It must be borne in mind that coagulation is a complicated phenomenon involving quite a range of kinetic and specific ion effects. 

The reverse of the coagulation process is peptization. It is well known from analytical chemistry that fresh precipitates are easier to disperse than old ones, which indicates qualitatively that an aggregate of colloidal particles is not in equillibrium and that irreversible, time-dependent processes occur in coagulation. As pointed out Frens and Overbeek (1971) the interpretation of peptization phenomena with aggregated systems is not possible unless the data are obtained in experiments with a shorter time scale than the aging time of the aggregate. They demonstrated that it was possible to follow the kinetics of peptization by suddenly diluting the sol... 

In contrast, no anticoagulants were used in our experiments. Dif-fusional phenomena probably did not play a controlling role when the entire coagulation system was active, and biochemical and kinetic factors most likely dominated the long-term interaction between biomaterial and blood. In ex vivo experiments using a baboon model, Harker et al. (8) also found that... 

The following comparison of the predictions of this model with experiment has not been hitherto presented (no earlier test, e.g. in refs [1,48,77,78], took into account all of the effects of compartmentalization, coagulation, and the full models for entry and exit including aqueous-phase kinetics, although all of the cited references included some of these). The present test involves a comparison between model predictions and experiment for styrene emulsion polymenzation at 50 °C with Aerosol MA (the trade name of the dihexyl ester of sodium sulfo-succinic acid, Cytec) as surfactant. For this system, Os = 45 [79], the cmc... 

This layer, which is termed the diffuse electrical double layer, can be described mathematically by the Poisson-Boltzmann equation. Within this layer, the shear plane of the particles is located. The potential at this distance from the surface is particularly important as it is the experimentally accessible zeta-potential. When two different colloidal particles that are electrically charged at their surfaces with ions of the same sign approach each other, they wiU experience a net repulsion force as a result of the interaction between the ions located at their diffuse layers. If the net interaction potential between the particles is repulsive and larger than the kinetic energy of the collision, they wiU not coagulate. 

The kinetic data from this experiment is shown in Fig. 3.1.7, resulting in the RlO-1 product (Section 3.1.4.2). Its GPC trace is shown in Fig. 3.1.11, which indicates a material with a relatively high molecular weight and a reasonable PDI of 1.97. When the reactor product was coagulated in water with KOH, the coagulum can be drawn into a fibrous material. This is probably due to the development of microcrystalline domains of potassium acrylate in the polymer, as evidenced by a melting transition at 47°C. 

Smoluhovsky, M. Experience of the mathematical theory of kinetics of concretion of the colloid openings. Coagulation of CoUoids.M ONTl. 1936a, 7-39, (in Russian). 

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