Swelling dynamic

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

In a similar approach Riihe et al. [279] reported the preparation ofpoly(2-oxazoline) brushes by the grafting onto as well as grafting from method. For LCSIP of 2-ethyl-2-oxazolines silane functionalized undecane tosylate was first prepared and then immobilized on the substrate surface. SIP resulted in PEOx layers with thickness close to 30 nm. PEOx brushes were prepared by chemisorption of PEOx disulfides onto gold substrates. Preliminary static and dynamic swelling experiments are reported for these brushes. However, later observations [243] contradicted these findings. 

Dynamic swelling parameters of bioactive substances into hydrogel matrices are summarized in Table 19.1. The values of n>0.5 indicate that the loading mechanism of bioactive substances deviates from Fickian diffusion. For NIPA-APSA and NIPA-AA/Richlocaine systems the diffusion mechanism is relaxation-controlled because their n values are close to 1. Temperature-dependent release of richlocaine from the NIPA-AA hydrogels is shown in Figs. 19.3 and 19.4. 

Kim B, Flamme KL, Peppas NA (2003) Dynamic swelling behavior of pH-sensitive anionic hydrogels for protein delivery. J Appl Polym Sci 89 1606-1613... 

Peppas, N. and Korsmeyer, R., Dynamically swelling hydrogels in controlled applications, Hydrogels in Medicine and Pharmacy, Vol. 3. Properties and Applications, edited by N. Peppas, CRC Press, Boca Raton, 1987, pp. 109-136. 

Dynamic swelling method (DSM) None ST/DVB Ethanol/water [10,78-83]... 

The dynamic swelling method (DSM) [10] has also been described for the preparation of crosshnked microspheres with free vinyl groups [78]. Therefore, polystyrene seed particles (1.9 pm) prepared by dispersion polymerization are dispersed in ethanol-water (7/3, w/w) containing divinylbenzene (DVB), benzoyl peroxide, and poly(vinyl alcohol) (PVA). The slow drop-wise addition of water to the mixture causes the DVB phase to separate, and it is continuously imbibed by seed particles to produce relatively large swollen particles (4.3 pm), which are then polymerized to afford the respective PS-PDVB composite particles with free vinyl groups. DSM has recently been developed in order to prepare hohow microspheres and various oddly-shaped polymer particles, including a rugby ball, red blood cells, or snowman structures [79-83]. 

The porous latex seed particles are obtained via the dynamic swelling method followed by an emulsion polymerization process. A volatile solvent that has no tendency to take part in the polymerization is used in the swelling process and is followed by evaporation to prepare the porous microspheres [99]. The monodisperse particles can be swollen up to 50-1000 times with respect to their initial volume by a vinyl monomer solution, sometimes in combination with other reactants such as a porogen solvent. All reactants are present inside the swollen particles before polymerization. 

Okubo, M., Shiozaki, M., Tsujihiro, M., and Tsukuda, Y., Preparation of micron-size monodisperse polymer particles by seeded polymerization utilizing the dynamic swelling method. Colloid Polym. Sci., 269, 222-226 (1991). 

Okubo et al. examined the penetration/release behavior of various solvents in-to/from the interior of micron-sized monodisperse cross-linked polystyrene/poly-divinylbenzene composite particles [63]. The hollow particles were produced by the seeded polymerization utilizing the dynamic swelling method [64], Itou et al. prepared crosslinked hollow polymer particles of submicron size by means of a seeded emulsion polymerization [65]. The morphology of the particles depends on the composition of divinylbenzene and methyl methacrylate. 

Another approach for treating dynamic swelling hydrogels is to couple the Fickian diffusion with relaxation. One such model, by Berens and... 

For most Industrial applications, one is simply interested In knowing the extent of swelling (equilibrium swelling), but sometimes more information may be drawn from kinetics studies (dynamic swelling). This is so for pharmaceutical controlled drug release formulations, either the conventional compressed hydrophilic matrices [5, 26, 27] or the more recent swelling controlled systems [28-32]. 

The equiibrium and dynamic swelling behavior of lightly crosslinked copolymers of 2-hydroxyethyl methacrylate and acidic monomers have been studied as a function of pH at a constant Ionic strength of 0.1 M at 37°C. These gels showed pH-dependent equilibrium swelling behavior. Poly(2-hydroxyethyl methacrylate-co-acrylic acid) networks swelled as a function of time with rates dependent on pH. 

Figure 2 shows the influence of pH on the dynamic swelling behavior of P(HEMA-co-AA) copolymers containing 60 mol% HEMA. It can be seen that as the pH value increased, the water uptake rate increased as would have been expected from carboxyl ionization. 

Fig. 1. Dynamic swelling behavior of 50 50 mol% P(HEMA-co-MAA) (A) and 25 50 25 mol% P(HEMA-co-MAA-co-NaMA) ( ) copolymers measured at pH 7,06 and a total ionic strength of 0.1 M at 37°C.

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