Swelling characteristic theoretical

Komine H., Kurikami, H., Chijimatsu, M., Kobayashi, A., Sugita Y. and Ohnishi, Y. 2003. Coupled thermal, hydraulic and mechanical simulation with theoretical model for swelling characteristics, GeoProc 2003. 

COUPLED THERMAL, HYDRAULIC AND MECHANICAL SIMULATION WITH A THEORETICAL MODEL FOR SWELLING CHARACTERISTICS... 

The earliest theoretical framework developed to describe the equilibrium swelling characteristics of networks was that of Flory and Rehner [1] for a crosslinked polymer system with polymer chains prepared by reaction in the solid state. Such macromolecular chains exhibit a Gaussian distribution. 

In the following paper, the possibility of equilibration of the primarily adsorbed portions of polymer was analyzed [20]. The surface coupling constant (k0) was introduced to characterize the polymer-surface interaction. The constant k0 includes an electrostatic interaction term, thus being k0 > 1 for polyelectrolytes and k0 1 for neutral polymers. It was found that, theoretically, the adsorption characteristics do not depend on the equilibration processes for k0 > 1. In contrast, for neutral polymers (k0 < 1), the difference between the equilibrium and non-equilibrium modes could be considerable. As more polymer is adsorbed, excluded-volume effects will swell out the loops of the adsorbate, so that the mutual reorientation of the polymer chains occurs. 

Acetyl Celluloses (AC) (Acetates of Cellulose or Cellulose Acetates). According to Doree(Ref 3) the action of AcaO on cellulose (called acetylation) should theoretically yield the triacetate [CfiH702(00C. CH3)s]n. Actually, the products of acetylation are a mixture of tri-, di- and mono-acetate. A characteristic property of the lower acetyl-ated acetates is their sol in acetone, whereas the triacetate can absorb acetone only to the extent of causing swelling... 

The kinetic theory of rubber elasticity is so well known and exhaustively discussed (17, 27, 256-257, 267) that the remarks here will be confined to questions which relate only to its application in determining the concentration of elastically effective strands. In principle, both network swelling properties and elasticity measurements can provide information on network characteristics. However, swelling measurements require the evaluation of an additional parameter, the polymer-solvent interaction coefficient. They also involve examining the network in two states, one of which differs from its as-formed state. This raises some theoretical difficulties which will be discussed later. Questions on local non-uniformity in swelling (17) also complicate the interpretation. The results described here will therefore concern elasticity measurements alone. 

The colloidal characteristics of A -alkylacrylamide- or Af-alkylmethacrylamide-based particles are temperature related. In fact, the swelling ability, charge density, charge distribution, hydrophilic-hydrophobic balance, hydration and dehydration properties, particle size, surface polarity, colloidal stability, water content, turbidity, and electrokinetic and rheological properties are indis-cemibly temperature dependent. Such polymer particles can be used as a stimuli-responsive model for the investigation of colloidal properties and for theoretical studies. 

A previous study [8] has shown that the stopped-flow light-scattering method is well adapted to the evaluation of permeability of the lipid bilayer to water. The theoretical model shows that the swelling of vesicles resulting from an osmotic shock should follow first-order kinetics. Its characteristic half-time, <1 2. is the half-time of permeation of water through the membrane [8,9]. 

The water content is the state variable of PEMs. Water uptake from a vapor or liquid water reservoir results in a characteristic vapor sorption isotherm. This isotherm can be described theoretically under a premise that the mechanism of water uptake is sufficiently understood. The main assumption is a distinction between surface water and bulk water. The former is chemisorbed at pore walls and it strongly interacts with sulfonate anions. Weakly bound bulk-like water equilibrates with the nanoporous PEM through the interplay of capillary, osmotic, and elastic forces, as discussed in the section Water Sorption and Swelling of PEMs in Chapter 2. Given the amounts and random distribution of water, effective transport properties of the PEM can be calculated. Applicable approaches in theory and simulation are rooted in the theory of random heterogeneous media. They involve, for instance, effective medium theory, percolation theory, or random network simulations. 

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