Swelling macroscopic

But it was not to be. Try as we might, the difference in scattering lengths between the 6Li and 7Li isotopes was too small to permit us to measure the lithium ion distribution in the swollen state. We had to content ourselves with the results for the crystalline phase, where the behavior of the lithium ions is different from that of the larger alkali metal cations [27], Potassium and cesium ions bind directly to vermiculite clay surfaces rather than hydrating fully. Because only lithium-substituted vermiculites of the alkali metal series will swell macroscopically when soaked in water, it seems that interlayer cations must form fully hydrated ion-water complexes if the particles are to expand colloidally. This conclusion has since been supported... 

For small volume changes, the diffusion coefficient is constant and the D values determined by macroscopic swelling experiments are in a remarkable agreement... 

In a film, the cooperative effort of the different molecular motors, between consecutive cross-linked points, promotes film swelling and shrinking during oxidation or reduction, respectively, producing a macroscopic change in volume (Fig. 18). In order to translate these electrochemically controlled molecular movements into macroscopic and controlled movements able to produce mechanical work, our laboratory designed, constructed, and in 1992 patented bilayer and multilayer103-114 polymeric... 

Even when they have a partial crystallinity, conducting polymers swell and shrink, changing their volume in a reverse way during redox processes a relaxation of the polymeric structure has to occur, decreasing the crystallinity to zero percent after a new cycle. In the literature, different relaxation theories (Table 7) have been developed that include structural aspects at the molecular level magnetic or mechanical properties of the constituent materials at the macroscopic level or the depolarization currents of the materials. 

Thus, for the purposes of this chapter, a hydrogel is considered to be a polymeric material that can absorb more than 20% of its weight in water while maintaining a distinct three-dimensional structure. This definition includes dry polymers that will swell in aqueous environments in addition to the water-swollen materials which inspired the original definitions [3], A hydrogel that dries without significant collapse of the macroscopic structure and which absorbs water into... 

G Rossi, KA Mazich. Macroscopic description of the kinetics of swelling for a cross-linked elastomer or a gel. Phys Rev E 48 1182-1191, 1993. 

The parameters of neutron scattering theory of polymer networks are A, the macroscopic stretching of the sample, or linear degree of swelling, f, the network functionality, K. which accounts for restricted junction fluctuations and a, a measure of the degree to which chain extension parallels the macroscopic sample deformation. The functionality is known from knowledge of the chemistry of network formation, and A is measured. Both K and a must be extracted from experiments. 

A crucial requirement in future investigations is that macroscopic measurements of stress and swelling be performed on the same materials used for small angle neutron scattering. A sensible program for research is apparent. The work remains to be done. 

Fig. 4 Insert Representative macroscopic image of an APNP hydrogel scaffold seeded with human adipose-derived stem cells following 7 days of culture in a 12-well plate. Graph Osmotic swelling pressure profile of APNP hydrogel scaffolds (green-squares) compared to human NP (orange-triangles and red-diamonds) values found in the literature [28]...

J. van der Weerd and S.G. Kazarian, Validation of macroscopic attenuated total reflection-Fourier transform infrared imaging to study dissolution of swelling pharmaceutical tablets, Appl. Spectrosc., 58, 1413-1419 (2004). 

J. Quillet The swelling doesn t help you very much because it hasn t affected the mobility of the molecules. It has helped the macroscopic appearance of viscosity but not the microscopic. 

Swelling of Spherical Gels. Let us examine kinetics of the macroscopic instability at K = 0 in more details in a spherical gel with radius R immersed in solvent at zero osmotic pressure [18, 21, 46-49]. This should be appropriate because previous theories made no clear distinction between the two points, K = 0 and K + p = 0 [46-48]. The gel expands isotropically and the displacement vector u is assumed to be of the form,... 

Gels are very soft and can be easily deformed into anisotropic shapes. In such states, phase transitions and separation are of great interest. Similar problems have been treated in the metallurgical literature [57-59]. In this subsection, we are mainly interested in the structure factor in such deformed states, so we will neglect possible macroscopic instabilities (which can occur if gels are allowed to swell at least in two directions as will be discussed in Sect. 5). 

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