Microgels properties

As the form factor analysis provides detailed insight into the particle structure, one can use this information in order to adapt the polymerization conditions, as, for example, batch, semibatch synthesis, or controlled monomer feed, in order to tailor particle morphology and thus microgel properties.In addition, one can employ SANS data to investigate the influence of chemical reactivity on the microstructure by comparing, for example, different cross-linkers, initiators, or monomers. 

Influence of Comonomers on Microgel Properties. The overall physicochemical properties of a microgel depend not only on the cross-linker concentration, but also on the concentration of monomer/comonomers used in the synthesis. The addition of a small amount of comonomer (typically 1-5 wt% monomer) can have a dramatic effect on the overall properties of the resultant microgel particles. For example, a pH- and temperature-sensitive microgel can be prepared by copolymerizing poly(NIPAM) with acrylic acid. These spherical particles undergo... 

NIPAM and BA are shown to be consumed at different rates during synthesis resulting in possible non-imiform composition within particles [23]. Further discussion of this aspect of microgel properties can be found later on in this article (see Section 4.8 entitled Microgel Structure )... 

Saunders B R and Vincent B 1999 Microgel particles as model colloids theory, properties and applications Adv. Colloid Interface Sol. 80 1 -25... 

The treatment of blends as a two phase system opened up an interesting field of modifying the composite properties by the use of a (third component within the interface boundaries, which is termed as compatibilizers [1]. Such modifications are still being extended to the formation of microgel out of the interaction between the two blend partners having a reactive for functionalities. This type of interchain crosslinking does not require any compatibilizer to enhance the blend properties and also allows the blends to be reprocessed by further addition of a curative to achieve still further improved properties [3,4]. Such interchain crosslinking is believed to reduce the viscoelastic mismatch between the blend partners and, thus, facilitates smooth extrusion [5,6]. 

Xanthan has several undesirable properties. It ordinarily forms microgel particles that can plug permeability(137), it is expensive relative to other natural polysaccharide gel agents, and it resists degradation by ordinary gel breaker additives. These features have kept xanthan applications in fracturing gels to a minimum. Some literature(138) on xanthan has appeared. 

Therefore, in a crosslinking process which is governed by the intramolecular crosslinking, the structure of the microgels is important. Currently, gel formation is qualitatively quite well understood by using the knowledge about the properties of microgels. However, a satisfactory quantitative treatment is still desirable. 

Because the conditions of solubilization and copolymerization of EUP/ comonomer systems as well as the characteristics and properties of the microgels depend on a variety of parameters, these data are included in the following figures and their captions. 

Emulsion copolymerization of EUP and comonomers may be initiated in the aqueous (persulfate) or in the non-aqueous phase (AIBN). On the decomposition of persulfates, sulfate and hydroxyl groups are introduced into macromolecules and microgels, thus influencing their surface properties [118,123-125]. By using AIBN as initiator a change of the chemical character of the surface and of the properties of the microgels is avoided. 

Characterization and Properties of Microgels from Self-Emulsifying Unsaturated Polyesters and Comonomers... 

Microgels have also been detected as a component of alkyd resins, an early but still important binder of organic coatings [316-321] and are accountable for their ability to fill pores, fissures and other irregularities of the substrate such as wood. This property may be explained by the size of the microgels which prevents the paint becoming soaked up by the substrate. 

These examples show that microgels already played a role in the properties of important industrial polymers before they were intentionally added as a component. The more significant applications of microgels may be summarized as ... 

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