Kinetics of the swelling

Figure 11. Kinetics of the swelling of a polyacrylonitrile film in (1) a 50-50% mixture of acrylonitrile with toluene at 25°C (2) pure acrylonitrile at 25°C (3) pure acrylonitrile at 75°C (4) a 50-50% mixture of acrylonitrile with acetonitrile...

In isosmotlc solutions, movement of neutral amino acids such as prollne across the inner membrane into the matrix results in swelling of mitochondria (20). As shown in Figure 3C, the movement of proline is thought to occur via a uniport. The increased concentration of proline in the matrix produces an osmotic-induced swelling. Kinetics of the swelling response is shown in the 0 (control) trace. Again, quercetin inhibited this response in a concentration-dependent manner. 

In our recent publications [4, 5] we discussed results concerning ion and molecule mobility in cationic montmorillonite film modified electrodes hydrophobized with aliphatic and aromatic quaternary ammonium compounds. We also described experiences with independent measurements by electrochemical and radiochemical methods on transport processes in humate containing montmorillonite and bentonite thin layers [6]. We interpreted the results as consequences of changes in structure which lead to changes in porosity and ditfu-sional transport [7, 8, 9]. The present paper approaches the role of film thickness, and the kinetics of the swelling of films (porodine xerogels) at different levels of hydrophobization, and also the kinetics of the penetration and release of probe molecules. 

The swelling pattern considered above allows us to understand the peculiarities of the behavior of SAH and the effects encountered during their application. The kinetic aspects of swelling seem to be as important as the thermodynamics of this process. Therefore, we shall touch upon some problems concerning the kinetics of hydrogel swelling and deswelling. 

It has been shown that the kinetics of the spreading of a liquid on a rubber is largely dependent on viscoelastic dissipation in the wetting ridge of the substrate near the triple line. This behavior may, in practice, be slightly altered by moderate swelling that modifies the solid/liquid interactions for long contact times. 

The complexity of the swelling kinetics of hydrogels means that only the simplest cases can be modeled quantitatively. Thus this section focuses on identification of rate-influencing phenomena and data analysis rather than the extensive theoretical modeling of the kinetic phenomena that has been done on this subject. Reviews of theoretical modeling include those by Peppas and Korsmeyer [119], Frisch [120], and Windle [121],... 

A study of the reaction kinetics of the reaction of butyl isocyanate with wood has been performed (West and Banks, 1986 West and Banks, 1987). Reactions were performed without catalyst and using pyridine, triethylamine, 1,4-diazobicyclo [2,2,2-octane] or di-butyl-tin-diacetate as catalyst. The data showed that no catalyst was effective without the presence of a swelling solvent. Kinetic profiles were obtained, which were deconvo-luted to yield two component reaction curves. It was considered that these two curves represented reaction with lignin and the holocellulose component of the cell wall. 

The kinetics of swelling of gels is successfully described in the collective diffusion of equation which was discussed in Sect. 3.1. In the case of the swelling of... 

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,... 

We also examined the swelling and shrinking kinetics of the gels in the slurries in comparison to kinetics in pure water. The rates were reduced in slurry somewhat - swelling and shrinking diffusion coefficients dropped by 60-70%. But the rates were fairly independent of slurry concentration over the range of 20 to 70 wt % solids. 

Fig. 18 SFM height images (scale 20 nm) of representative surface structures in SV films after spin-coating from chloroform solution (a), and from toluene solution (b). (c) Comparison of the swelling kinetics of400-nm-thick SV films with starting micelle (triangles) and lamella (circles) morphologies...

Studies on glucose-induced polymer swelling have focussed on developing membranes that could serve in systems for controlled delivery of insulin to diabetics (3,4). It has been shown that hydrophobic methacrylate copolymers undergo a sharp swelling transition as the pH is decreased from 7 to 6 (3-7). However, the kinetics of the transition are too slow for the proposed application to glucose delivery. 

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