Swelling behavior

Nylon-11. Nylon-11 [25035-04-5] made by the polycondensation of 11-aminoundecanoic acid [2432-99-7] was first prepared by Carothers in 1935 but was first produced commercially in 1955 in France under the trade name Kilsan (167) Kilsan is a registered trademark of Elf Atochem Company. The polymer is prepared in a continuous process using phosphoric or hypophosphoric acid as a catalyst under inert atmosphere at ambient pressure. The total extractable content is low (0.5%) compared to nylon-6 (168). The polymer is hydrophobic, with a low melt point (T = 190° C), and has excellent electrical insulating properties. The effect of formic acid on the swelling behavior of nylon-11 has been studied (169), and such a treatment is claimed to produce a hard elastic fiber (170). 

Swelling Behavior. One way to visualize the interaction of solvents with PVP is to examine the effect the former have on lightly cross-linked PVP, as a model for the linear polymer (78). 

Cellulose layers are produced from native, fibrous or microcrystalline cellulose (Avicel ). The separation behaviors of these naturally vary, because particle size (fiber length), surface, degree of polycondensation and, hence, swelling behavior are all different. 

In the studies by Skipper et al. the number of water layers (and thus molecules) was fixed on the basis of experimental evidence consequently, the stable states or degrees of swelhng were presumed. Quite differently, Karaborni et al. [44] determined, by means of a combination of GCMC and MD, the number of water molecules directly from a series of simulations in which the distance between montmorillonite planes was varied systematically. They observed that swelling proceeded from the dry state through the formation of one, three, and then five layers of water. This is very different from the usually beheved hydration sequence from one layer to two, then to three layers, and so on, which has been intrinsically assumed by Skipper and coworkers. The authors conclude that the complex swelling behavior accounts for many of the experimental facts. This work demonstrates impressively the power of the grand canonical simulation method. 

In addition to monomers and the initiator, an inert liquid (diluent) must be added to the monomer phase to influence the pore structure and swelling behavior of the beaded resin. The monomer diluent is usually a hydrophobic liquid such as toluene, heptane, or pentanol. It is noteworthy that the namre and the percentage of the monomer diluent also influence the rate of polymerization. This may be mainly a concentration or precipitation effect, depending on whether the diluent is a solvent or precipitant for the polymer. For example, when the diluent is a good solvent such as toluene to polystyrene, the polymerizations proceed at a correspondingly slow rate, whereas with a nonsolvent such as pentanol to polystyrene the opposite is true. 

A representative example of the extrudate swelling behavior is shown in Fig. 15 as a function of blend ratio... 

The main property of agricultural SAH is their ability to absorb, retain in the swollen state, and then to transfer large volumes of water, in other words, their swelling behavior in a broad sense. In this section, we consider the main features of the behavior including, when necessary, some fragments of the theory of these systems and methods of their structural analysis. 

The swelling behavior of hydrogels in solutions of multivalent ions capable to associate with the network-fixed charges, e.g., Cu2+, substantially differs from that described above, viz. the collapse of gels takes place [107]. As a result of this... 

These examples show once again that the network-fixed charges play an important role in the swelling behavior of hydrogels. 

This process is highly suitable for rubbers with poor solubility. In this process, the rubber sheet is soaked in TEOS or quite often in TEOS-solvent mixture and the in situ sUica generation is conducted by either acid or base catalysis. The sol-gel reaction is normally carried out at room temperature. Kohjiya et al. [29-31] have reported various nonpolar mbber-silica hybrid nanocomposites based on this technique. The network density of the rubber influences the swelling behavior and hence controls the silica formation. It is very likely that there has been a graded silica concentration from surface to the bulk due to limited swelling of the rubber. This process has been predominantly used to prepare ionomer-inorganic hybrids by Siuzdak et al. [48-50]. 

Baker, JP Hong, LH Blanch, HW Prausnitz, JM, Effect of Initial Total Monomer Concentration on the Swelling Behavior of Cationic Acrylamide-Based Hydrogels, Macromolecules 27, 1446, 1994. 

In the first place the ease of these reactions depends on the swelling behavior of the polymeric support. If the liquid employed for dissolving the metal precursor swells the support to a relatively high extent, the interior of the swollen polymer will be readily accessible (Figure 7) [30]. 

The lack of quantitative success of the theory presented in the previous section is primarily the result of inadequacies in the mixing and elasticity terms. Sophisticated theoretical expressions are available which afford much improved predictions of swelling behavior. However, even these theories are not particularly successful when applied to hydrogels. Here the limitations of the theory presented in Section III.A.l will be identified. 

BG Kabra, SH Gehrke, ST Hwang, WA Ritschel. Modification of the dynamic swelling behavior of PHEMA. J Appl Polym Sci 42 2409-2416, 1991. 

TA Horbett, J Kost, BD Ratner. Swelling behavior of glucose sensitive membranes. In SW Shalaby, AS Hoffman, BD Ratner, TA Horbett, eds. Polymers as Biomaterials. New York Plenum Press, 1984, pp 193-207. 

DC Harsh, SH Gehrke. Modeling swelling behavior of cellulose ether hydrogels. In M El-Nokaly, D Piatt, B Charpentier, eds. Polymeric Delivery Systems. ACS Symp Ser 520. Washington, DC American Chemical Society, 1993, pp 105-134. 

Doi and his coworkers have proposed a semiquantitative theory for the swelling behavior of PAANa gels in electric fields [14]. They have considered the effect of the diffusion of mobile ions due to concentration gradients in the gel. First of all, the changes in ion concentration profiles under an electric field have been calculated using the partial differential Equation 16 (Nernst-Planck equation [21]). 

Solvent Resistance. One of the distinct advantages of a crystalline thermoplastic elastomer over an amorphous one should be its superior solvent resistance, since the latter types are generally soluble. Table III shows the swelling behavior of the H2-BIB triblocks in toluene at 25°C. It can be seen that the maximum swelling obtained was in the case of the H2-BIB-34, which had the lowest end-block content. Furthermore, the equilibrium swelling ratio of 3-26 obtained for this polymer is considerably less than the value of 5 or 6 generally exhibited by a well-vulcanized natural rubber. 

It is always easy to calculate idealized scattering curves for perfect networks. The experimental systems vary from the ideal to a greater or lesser degree. Accordingly, any estimate of the correctness of a theoretical analysis which is based on an interpretation of experiment must be put forth with caution since defects in the network may play a role in the physical properties being measured. This caveat applies to the SANS measurement of chain dimensions as well as to the more common determinations of stress-strain and swelling behavior. 

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