Swelling studies

Equations (4.22) and (4.22 ) are predicated on the assumptions that both networks are continuous in space, network II swells network I, and that the swelling agent then swells both networks. The several PS/PS IPNs under consideration constitute an excellent model system with which to examine fundamental polymer parameters. Questions of interest in the field of IPNs relate to the relative continuity of networks I and II and their consequent relative contribution to physical properties and the extent of formation of physical crosslinks or actual chemical bonds between the two networks. If equations (4.22) and (4.22 ) are obeyed exactly, the implicit assumptions require that both networks be mutually dissolved in one another and yet remain chemically independent. Then the only features of importance are the crosslink densities and the proportions of each network. 

Investigator Added physical crosslinks Network I domination  

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Puskas, J.E. Dendritic (arborescent) pol3tisobutylene-polystyrene block copolymers DMTA analysis and swelling studies, Polym. Mater. Sci. Eng., 91, 875-876, 2004. 

CM Ofner III, H Schott. Swelling studies of gelatin. I Gelatin without additives. J Pharm Sci 8 790-796, 1986. 

Gebel, G., Aldebert, P. and Pineri, M. 1993. Swelling study of perfluorosulpho-nated ionomer membranes. Polymer 34 333-339. 

In the solvent swelling study each coal was soaked In excess deuterated pyridine In a sealed glass ampoule for approximately two months before NMR measurements were made at room temperature. 

In many ways, the molecular models that we have used as the basis for our CAMD studies describe coal structure very well. However, none of the models investigated thus far contains explicit three-dimensional covalent cross-links. Actualfy, the models we have studied are primarily constructed of long chains of one-dimensionally-linked clusters with a number of short side-chains. However, it has been established on the basis of solvent swelling studies (11.15.16) that bituminous coal is primarily made up from a three-dimensional network of clusters held together by covalent bonds and by an even higher density of hydrogen bonds. These macromolecular models of coal, which are less concerned with the molecular structure than with the ways that clusters are bonded to one another, provide a complementary way of describing coal structure. 

Such techniques have been tried with solid propellants, but reproducible results depend on attaining complete binder-filler release and adequately measuring the binder sol fraction. Preliminary swelling studies to determine a solvent system and conditions which do not degrade the propellant are required. Common extraction techniques are used to determine the sol fraction. This determination is then applied as a correction when computing crosslink density. The force-deformation relationship for swollen rubbers is... 

Sperm evaluations routinely include data on sperm number, morphology and motility (Berman etal., 1996). Testicular spermatid count or cauda epididymal weight are other useful measures of sperm production, but no surrogate measures are adequate to evaluate sperm morphology or motility. A number of other indices of sperm function have been employed (e.g., sperm-zona interactions, acrosome reaction, sperm swelling studies), but these have been of limited utility and infrequently used and have not been incorporated into any testing guidelines. 

Summarizing this section, we conclude that, from an experimental point of view, the ideal network theory expressed by Eq. (III-9) seems to be obeyed rather well only in the case of swollen networks. The determination of the elasticity parameters is complicated by the presence of a free enthalpy of dilution term. In spite of this, it is possible to conclude that 1/2 is the most likely value for B in Eq. (III-9). The factor A remains undetermined because experimentally the most one can obtain is A g o 2 8. Concerning this memory parameter, a dependence on the stage of dilution during crosslinking definitely exists, (Eq. Ill-19), but its dependence upon the nature of the diluent used in swelling studies needs further investigation. 

Martinac, A., Filipovic-Grcic, J., Perissutti, B., Voinovich, D., and Pavelic, Z. (2005), Spray-dried chitosan/ethylcellulose microspheres for nasal drug delivery Swelling study and evaluation of in vitro drug release properties,/. Microencapsul., 22, 549-561. 

The rate and extent of granule swelling is also an interesting factor. The swelling power depends on the variety of starch and is not well understood. Figure 34 presents the results of swelling studies of a few thick-boiled starches.437... 

Ofner CM3d, Schott H. Swelling studies of gelatin. II Effect of additives. / Pharm Sci 1987 76(9) 715-723. 

Chomakova-Haefke, M. Nyffenegger, R. Schmidt, E. Structure reorganization in polymer films of Nation due to swelling studied by scanning force microscopy. Appl. Phys. A 1994, 49. 

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