Polymer transport behavior

Figure 18 shows the temperature dependence of the proton conductivity of Nafion and one variety of a sulfonated poly(arylene ether ketone) (unpublished data from the laboratory of one of the authors). The transport properties of the two materials are typical for these classes of membrane materials, based on perfluorinated and hydrocarbon polymers. This is clear from a compilation of Do, Ch 20, and q data for a variety of membrane materials, including Dow membranes of different equivalent weights, Nafion/Si02 composites ° ° (including unpublished data from the laboratory of one of the authors), cross-linked poly ary lenes, and sulfonated poly-(phenoxyphosphazenes) (Figure 19). The data points all center around the curves for Nafion and S—PEK, indicating essentially universal transport behavior for the two classes of membrane materials (only for S—POP are the transport coefficients somewhat lower, suggesting a more reduced percolation in this particular material). This correlation is also true for the electro-osmotic drag coefficients 7 20 and Amcoh...

The electrostatic forces also play an important role in the conformation and structure of macromolecules such as polymers, polyelectrolytes, and proteins. The self-assembly of proteins from disks to virus is triggered by electrostatic interactions between neighboring subunits. In the case of polyelectrolytes (polymer molecules with charges) and charged colloids, transport behavior such as rheology is also affected significantly by charge effects, as we have already seen in Chapter 4. 

While to some extent the boundary between light and heavy penetrant molecules in polymers appears arbitrary, theoretical explanations of the transport behavior of the latter tend to be more complex. 

For polystyrene fractions in diethyl phthalate solution (30000average value of 1.6 x 10 18 ( 50%). In dilute solution e/36M is 1.27 x 10 18 for polystyrene (21). No systematic variations with concentration, molecular weight or temperature were apparent, the scatter of the data being mainly attributable to the experimental difficulties of the diffusion measurements. The value of Drj/cRT for an undiluted tagged fraction of polyfn-butyl acrylate) m pure polymer was found to be 2.8 x 10 18. The value of dilute solution data for other acrylate polymers (34). Thus, transport behavior, like the scattering experiments, supports random coil configuration in concentrated systems, with perhaps some small expansion beyond 6-dimensions. 

We describe here that the redox oligomer wires fabricated with the stepwise coordination method show characteristic electron transport behavior distinct from conventional redox polymers. Redox polymers are representative electron-conducting substances in which redox species are connected to form a polymer wire.21-25 The electron transport was treated according to the concept of redox conduction, based on the dilfusional motion of collective electron transfer pathways, composed of electron hopping terms and/or physical diffusion.17,18,26-30 In the characterization of redox conduction, the Cottrell equation can be applied to the initial current—time curve after the potential step in potential step chronoamperometry (PSCA), which causes the redox reaction of the redox polymer film ... 

The distribution of free volume in amorphous polymers is of paramount importance for the respective material s transport behavior towards small and medium-sized penetrants. 

The structure of the low bandgap polymeric semiconductor and the dopant dye is plotted in Fig. 5.19. The average thickness of the active layers, determined by AFM measurements, is between 80 and 110 nm. In order to obtain a better understanding of the transport behavior of polymer blends, low temperature studies of cells with pristine MDMO-PPV and MDMO-PPV/PTPTB 1 1 (wt. %) with Au electrodes were carried out. Au has a high work function and should therefore be a good hole injection contact and provide a high barrier for electron injection. The device will therefore be a hole-only device, as described earlier in this chapter [14]. 

These two effects are summarized in Table 20.4-8. Moreover, the percentage reduction in flux for each component dne to nonideal gas-phase effects is listed in Table 20.4-8. Ii is clear ther the redaction in fugacity driving force is very smell (0.5%) for methane, which tends to he an ideal gas under these conditions. For CO2, however, rhe effects amonnt 10 roughtly 7,5% and account for a roughly 6,9% reduction in the ides] separation factor. To reemphasize, these effects would be observed even if the polymer-phase sorption and transport behavior did not show dual-mode effects and were perfectly ideal. 

H. Itou, M. Toda, K. Ohkoshi, M. Iwata, T. Fujimoto, Y. Miyaki and T. Kataoka, Artificial membranes from multiblock copolymers. 6. Water and salt transport through a charge-mosaic membrane. Ind. Eng. Chem. Chem. Res., 1988, 27, 983-987 K. Ishizu and M. Iwade, Transport behavior of electrolytes through charged mosaic composite membranes, Polym. Plast. Technol. Eng., 1995, 34, 891-915. 

The thermodynamic interactions and the size of polymer coil enter dependencies that describe the transport behavior of polymer solutions, viz. viscosity, diffusion, sedimentation, etc. To complete this short summary, the intrinsic viscosity should be mentioned. 

Magnetic and Electron Transport Behaviors of Conductive-Polymer Nanocomposites... 

Unquestionably, Yamakawa and collaborators have made a substantial contribution to the understanding of transport behavior of semi-flexible polymers in dilute solution. However, their theories still leave something to be desired, as revealed by the recent careful experiments mentioned above. Their formulation is essentially the combination of the the Kirkwood-Riseman hydrodynamics and the statistics of wormlike chains. As mentioned in Chapter 2, this hydrodynamics fails to be good for flexible chains, but we have seen that it seems to work well for stiff chains. The reason is that the Kirkwood-Riseman formalism gives the exact solution in the limit of rigid rods. 

P.V. Anil Kumar, S. Anilkumar, K.T. Varughese, S. Thomas. Transport behavior of aromatic hydrocarbons through high density polyethylene/ ethylene propylene diene terpolymer blends. Journal of Polymer Research 2012 19 9794... 

MIP membranes prepared via alternative imprinting (cf Section III.D.2) showed a more complex transport behavior. Yoshikawa et al. had developed specifically synthesized polystyrene resins with chiral tetrapeptide recognition groups, which had to be used in blends with a matrix polymer for membrane formation via a dry PI process. The resulting membranes seemed to be microporous and had a low permeability (seeTable 1). 

For many applications of filled polymers, knowledge of properties such as permeability, thermal and electrical conductivities, coefficients of thermal expansion, and density is important. In comparison with the effects of fillers on mechanical behavior, much less attention has been given to such properties of polymeric composites. Fortunately, the laws of transport phenomena for electrical and thermal conductivity, magnetic permeability, and dielectric constants often are similar in form, so that with appropriate changes in nomenclature and allowance for intrinsic differences in detail, a general solution can often be used as a basis for characterizing several types of transport behavior. Useful treatments also exist for density and thermal expansion. 

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