Microgels, reactive

In Fig. 48, the regions of the formation of linear or branched polymers, microgels and macrogels are shown as a function of the concentration of 1,4-DVB and of n-BuLi. Reactive microgels can be obtained at a monomer concentration below 50 g/1 and between 3 and 16 mol % of n-BuLi. The polymer structure approaches that of a macrogel when the concentration of 1,4-DVB or n-BuLi is increased. 

Almost linear polymers with pendant vinyl groups are formed as intermediates in the anionic polymerization of 1,4-DVB due to the different reactivities of monomers and pendant vinyl groups. 1,4-DVB microgels are formed towards the end of monomer conversion. In the anionic polymerization of EGDM or 1,3-DVB, reactive microgels are formed already at the beginning of the polymerization. 

Only a few publications have appeared in which for the synthesis of reactive microgels other monomers were used than 1,4-DVB or EDMA. Hiller and Funke studied the anionic polymerization of 1,4-diisopropenylbenzene (1,4-DIPB) by n-BuLi in 1,2-dimethoxyethane and by sodium naphthalene in THF [231]. 

As carriers for proteins and enzymes biocompatible reactive microgels must be synthesized which are soluble in the serum at 37 °C. Moreover they should be hydrophilic enough that no ionic monomers are needed but they should not be soluble in water. An inert comonomer should serve as a spacer as well as a reactive solvent that may dissolve solid comonomers. The coupling reaction should be possible under mild reaction conditions. 

The industrial production and application of reactive and non-reactive microgels in organic coatings such as binders or components of binders, e.g. together with, e.g. acrylic and/or melamine/formaldehyde resins, especially for automotive coatings, was reported in a number of publications between 1980 and... 

Reactive microgels may be incorporated into plastics by covalent bonds. It could be demonstrated that substantial amounts of polymer chains from bifunctional monomers can be attached at microgel surfaces and thus become insoluble [313, 377-380]. 

Emulsion Polymerization of Multifimctional Monomers-Preparation of Reactive Microgels... 

Reactive microgels are crosslinked polymer particles which have a diameter of some 100 A and contain pendant reactive groups like vinyl groups. Such microgels may be copolymerized with bifunctional monomers to obtain crosslinked polymers in which the microgel particles act as multifunctional cross-linking sites (J ). In some respects such crosslinked polymers are comparable with other multiphase polymer systems like block or graft polymers. 

In both cases the isolation of the reactive microgels from the reaction batch requires careful and elaborate series of procedures at low temperatures in the absence of oxygen (1,3). Otherwise the reactive particles will agglomerate irreversibly. 

Micelle-forming materials obtained by radical copolymerization of sodium salt of AMPS with 9-vinylphenanthrene and 1-vinylpyrene (AIBN, THE solvent, 60°C) can be used as media for photosensitized electron transfer in aqueous systems (166). Reactive microgels obtained by copolymerization of AMPS with N -methyleneacrylamide are suitable for the immobilization of biological materials (167). 

The addition of an inert solvent is usually ineffective since phase separation may occur >f40) jiyj eventually lead to the formation of reactive microgels and macroporous structures which find application, for example, in resins for ion exchange and column packings for size elusion chromatography... 

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