Polymer Swelling Kinetic studies

Amines can also swell the polymer, lea ding to very rapid reactions. Pyridine, for example, would be a fairly good solvent for a VDC copolymer if it did not attack the polymer chemically. However, when pyridine is part of a solvent mixture that does not dissolve the polymer, pyridine does not penetrate into the polymer phase (108). Studies of single crystals indicate that pyridine removes hydrogen chloride only from the surface. Kinetic studies and product characterizations suggest that the reaction of two units in each chain-fold can easily take place further reaction is greatiy retarded either by the inabiUty of pyridine to diffuse into the crystal or by steric factors. 

To summarize, we have shown that proton transport and reaction with unionized amines is often a decisive factor in determining swelling rates in the hydrophobic amine gels we have studied. Simple explanations based on solvent diffusion and polymer relaxation, although useful for nonionic polymers, cannot account for swelling kinetic phenomena in initially dry polyelectrolyte gels. 

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. 

By combining thermodynamically-based monomer partitioning relationships for saturation [170] and partial swelling [172] with mass balance equations, Noel et al. [174] proposed a model for saturation and a model for partial swelling that could predict the mole fraction of a specific monomer i in the polymer particles. They showed that the batch emulsion copolymerization behavior predicted by the models presented in this article agreed adequately with experimental results for MA-VAc and MA-Inden (Ind) systems. Karlsson et al. [176] studied the monomer swelling kinetics at 80 °C in Interval III of the seeded emulsion polymerization of isoprene with carboxylated PSt latex particles as the seeds. The authors measured the variation of the isoprene sorption rate into the seed polymer particles with the volume fraction of polymer in the latex particles, and discussed the sorption process of isoprene into the seed polymer particles in Interval III in detail from a thermodynamic point of view. 

Katime, L Novoa, R. Zuluaga, F. Swelling kinetics and release studies of theophylline and aminophylline from acrylic acid/n-alkyl methacrylate hydrogels. Eur. Polym. J. 2001, 37, 1465-1471. 

Extracting hydrophobic gels prepared by swelling cross-linked polybutadiene with solutions of 4-acylpyrazol-5-one (HL) in toluene, chloroform, and carbon tetrachloride were used for copper extraction studies [192]. The metal distribution curves, close to those obtained in the pure liquid-liquid extraction systems, show that the polymer has no effect on the thermodynamics of the liquid-gel extraction, as shown in Fig. 43. Kinetic studies... 

The study of the effect of the addition of PVA and clay to the cement-water hydration was done. A general and empirical method for determining the kinetic parameters was used. The apparent activation energy was higher for the case of the polymer and polymer-clay addition than clay and pristine cement paste. The maximum adiabatic temperature reached was for the case of cement-water and clay sample. The polymer swells and produces a film around the cement and delay the cement hydration. Instead, clay acts as nucleating agent and produces a high hydration rate. The addition of clay to PVA did not affect the hydration kinetics. 

Sheppard, N. F., Jr., and Lesho, M. J., A method for studying. swelling kinetics based on measurement of electrical conductivity, Polym. Gels Networks, submitted. 

This snbchapter presents the results of theoretical and experimental studies on the influence of solvent properties on the nature of the swelling kinetics for elastomeric polymer networks at finite strains of the polymer matrix. Emphasis is focused on the study of the relationship of the asymptotic properties of the swelling kinetic curves with the thermodynamic quality of a solvent. The chemical potential of a solvent in the sample under swelling is given by the following equation ... 

Figure 6.6.4 shows the results of a study of the kinetics of absorption of low-molecular-mass liquid by polymer. It can be seen that all swelling kinetic curves plotted in the coordinates ( /t g), have an initial linear stage, i.e., kinetic curves are normal sorption ones. Consequently, the experimental values of the diffusion coefficient D, can be calculated using equation [6.6.8]. Figure 6.6.5 shows the swelling kinetic curves plotted in the coordinates (t -ln(l - g)). They take the shape of straight lines with a slope coefficient k at... 

The effect of the thermodynamic quality of solvent on the swelling kinetics of elastomeric polymer networks was theoretically and experimentally studied. Swelling is considered as a set of interrelated processes of diffusion and strain of a material. It is shown that the quality of a solvenf estimated by the Floiy-Huggins parameter value, significantly affects the nature of kinetic curves of polymer network swelling. 

RA Siegel. Hydrophobic weak polyelectrolyte gels—Studies of swelling equilibria and kinetics. Adv Polym Sci 109 233-267, 1993. 

In their study of branched PSA, Maniar et al. (1990) found that the molecular architecture of branched polymers affects the release kinetics in a variety of ways. They found that the branched polymers degraded faster than linear PSA of comparable molecular weight (Maniar et al., 1990). They also noted that drug (morphine) release profiles were more characteristic of bulk erosion than surface erosion An initial lag time during which very little drug was released was associated with the time required for water to swell the polymer. This was followed by a period of relatively fast release, which tapered off as the device disintegrated. The polymer matrix lost its mechanical integrity before the release experiment was complete (Maniar et al., 1990). Despite the increase... 

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