Monomers diffusion coefficient

The differences between the mathematical and experimental results can result from the fact that various parameters of the mathematical model (e.g. the monomer diffusion coefficient) do not change with time as they do over the course of the experiment. Also, various parameters such as the monomer diffusion coefficient and the initiator efficiency, f, are obtained from literature where the experimental conditions, e.g. the solvent and/or cure temperature, are not the same as our experimental conditions. 

The characteristic time of the exchange of monomer from droplets during Ostwald ripening (rex) is given by the following relationship, where is the dimensionless solubility of the monomer in water (0w = Cwi mon) and Dmon is the monomer diffusion coefficient ... 

DpOL Monomer diffusion coefficient in polymer phase [m s- l... 

Models of polymer dynamics are also partitioned by their assumptions as to the dominant forces in solution, these assumptions being totally independent of the assumed concentration dependence. In some models, excluded-volume forces (topological constrmnts) dominate, while hydrodynamic interactions dress the monomer diffusion coefficient. In other models, hydrodjmamic interactions dominate, while chcun-crossing constriunts cure secondary. Experimentally, Dg c) is directly accessible, but the intermolecular forces Ccm at best only be inferred from numerical coefficients D, a, and so forth. 

The parameters c, F, D, and Z>l represent the bulk concentration, equilibrium surface excess, monomer diffusion coefficient of surfactant for short times, and monomer diffusion coefficient of surfactant for long times,... 

Here is the monomer diffusion coefficient of an acrylate in bulk monomer and... 

In Equation 3.26, T is the equilibrium surface excess, C the bulk concentration, t the time, and D the surfactant monomer diffusion coefficient. Eastoe et al. have measured the time dependence of the DST and the relaxation time %2 for solutions of many surfactants nonionic, dimeric, and zwitterionic. In all instances the fitting of the data to Equation 3.26 with the experimentally determined value of %2 was poor. The authors concluded that the micelle dissociation may have an effect on the measured DST only if the concentration of monomeric surfactant in the subsurface diffusion layer is limiting or when the micelle lifetimes are extremely long. No surfactant for which this last condition is fulfilled was evidenced by the authors. They also concluded that the rapid dissociation of monomers from micelles present in the subsurface was not likely to limit the surfactant adsorption and thus the DST. 

Limitations on neutron beam time mean that only selected surfactants can be investigated by OFC-NR. However, parametric and molecular structure studies have been possible with the laboratory-based method maximum bubble pressure tensiometry (MBP). This method has been shown to be reliable for C > 1 mM.2 Details of the data analysis methods and limitations of this approach have been covered in the literature. Briefly, the monomer diffusion coefficient below the cmc, D, can be measured independently by pulsed-field gradient spin-echo NMR measurements. Next, y(t) is determined by MBP and converted to F(0 with the aid of an equilibrium equation of state determined from a combination of equilibrium surface tensiometry and neutron reflection. The values of r(f) are then fitted to a diffusion-controlled adsorption model with an effective diffusion coefficient which is sensitive to the dominant adsorption mechanism 1 for... 

Notably, an expression quite similar to Equation 13.3 for low surface pressures O follows from the model that accounts for the influence of micelles (assuming fast micelle disintegrationldnetics) on the effective monomer diffusion coefficient [25,42] ... 

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