Dynamic swelling method

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. 

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. 

In addition to the above techniques, inverse gas chromatography, swelling experiments, tensile tests, mechanical analyses, and small-angle neutron scattering have been used to determine the cross-link density of cured networks (240—245). Si soHd-state nmr and chemical degradation methods have been used to characterize cured networks stmcturaHy (246). H- and H-nmr and spin echo experiments have been used to study the dynamics of cured sihcone networks (247—250). 

To prove the hydrophobizing avoiding swelling, a complementary method was used that characterizes dry photoresist layers after short contact with the surfactant solution. Unexposed photoresist samples and photoresist processed with 70-96% and 100-110% of the threshold dose were inserted for 3 minutes in surfactant solutions of different concentrations. Then the solutions were removed quickly by a nitrogen flow. The contact angle of sessile water drops on the dried layers was measured using a fast dynamic method. 

Many different methods can be used to measure the degree of crosslinking within an epoxy specimen. These methods include chemical analysis and infrared and near infrared spectroscopy. They measure the extent to which the epoxy groups are consumed. Other methods are based on the measurements of properties that are directly or indirectly related to the extent and nature of crosslinks. These properties are the heat distortion temperature, glass transition temperature, hardness, electrical resistivity, degree of solvent swelling and dynamic mechanical properties, and thermal expansion rate. The methods of measurement are described in Chap. 20. 

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