Microgel application

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

The resulting microgel-stabilized metal nanoclusters are easily isolated, stored and further manipulated. Their remarkable catal5dic activity in technologically relevant reactions, such as C-C couplings [13a- ] and selective oxidations with molecular oxygen [13e] has been demonstrated. Extension of the applications of these nanoparticles to other areas of catalysis and materials science is currently underway. 

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. 

The experimental data obtained with macrogels formed in the presence of solvents, agreed well with Eq. (5) [99,105,108]. In order to check the applicability of this equation to microgels, the experimental data reported by Hoffmann [70] are used. He prepared a series of microgels with different crosslink densities, using toluene as a solvent, at Q°° = 5. Qvwas calculated from the reported data... 

The pendant vinyl groups at the surface of microgels can be modified in various ways according to the purpose of their application. 

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 ... 

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... 

An interesting way to prepare shock-resistant coatings [381] follows the synthesis of the ABS-terpolymers, e.g. shock-resistant polystyrene, where a soft, elastomeric phase is incorporated in a hard polymer matrix via covalent bonds. Because organic coatings solidify in situ, elastomeric microgels have been synthesized and mixed to a binder which forms the hard matrix phase before the application of this mixture as a coating material. 

Microgels are distinguished from linear and branched macromolecules by their fixed shape which limits the number of conformations of their network chains like in crosslinked polymers of macroscopic dimensions. The feature of microgels common with linear and branched macromolecules is their ability to form colloidal solutions. This property opens up a number of methods to analyze microgels such as viscometry and determination of molar mass which are not applicable to the characterization of other crosslinked polymers. 

Microgels which have been prepared in emulsions or microemulsion have a more compact structure than those obtained by polymerization in solution. For microemulsion copolymerization, preferentially self-emulsifying comonomers, such as unsaturated polyesters, are used as polymerizable surfactants, because no emulsifier must be removed after the reaction. By choosing suitable monomer combinations the composition, size and structure of microgels can be widely varied, thus adjusting these macromolecules to special applications. 

Hydrogels, 13 729-759. See also Microgels Superabsorbent polymers (SAPs) AMPS polymer, 23 721 applications for, 13 747-753 biodegradable, 13 739-742 bioerodible, 9 63 conducting, 7 524 cross-linked poly (ethylene oxide),... 

Microfluidic devices, 26 959 effect of scale on, 26 960t fabrication of, 26 963-966 Microfluidics, 26 959-980 applications of, 26 966-975 basic features of, 26 959-966 future directions for, 26 976-977 history of, 26 959 industrial impact of, 26 976 Microfluidic structures fabrication of, 26 963-966 MicroFluidic Systems, 26 976 Micro-gas chromatography (micro-GC), 6 434 37 Microgel particles... 

Improvement in the processing and vulcanized qualities of a range of systems have been reported over the past decades. Modification of natural rubber, due to work in the British Rubber Producers Research Association, yields some of the most striking applications of microgel. A detailed study at the MV Lomonosov Institute of Fine Chemical Technology, in Moscow, on the effect of microgels on mechanical properties of cis-polyisoprene and butadiene-styrene rubbers extensively illustrates the properties of blends from latex combination of microgel and conventional or linear systems.(31)... 

In a related application, polyelectrolyte microgels based on crosslinked cationic poly(allyl amine) and anionic polyfmethacrylic acid-co-epoxypropyl methacrylate) were studied by potentiometry, conductometry and turbidimetry [349]. In their neutralized (salt) form, the microgels fully complexed with linear polyelectrolytes (poly(acrylic acid), poly(acrylic acid-co-acrylamide), and polystyrene sulfonate)) as if the gels were themselves linear. However, if an acid/base reaction occurs between the linear polymers and the gels, it appears that only the surfaces of the gels form complexes. Previous work has addressed the fundamental characteristics of these complexes [350, 351] and has shown preferential complexation of cationic polyelectrolytes with crosslinked car-boxymethyl cellulose versus linear CMC [350], The departure from the 1 1 stoichiometry with the non-neutralized microgels may be due to the collapsed nature of these networks which prevents penetration of water soluble polyelectrolyte. 

The use of enzymatic tracers for ILAs has not yet been exploited to a large extent, probably due to the limitations associated with the effective competition of the analyte and its labeled derivative for the polymer binding sites. The availability of nanoparticles and microgels that can be used in homogeneous assays and allow a much better accessibility of the tracer to the selective sites in the MIP will certainly help to extend their application to highly sensitive detection of analytes. 

Abstract Molecular imprinting has grown considerably over the last decade with more and more applications being developed. The use of this approach for the generation of enzyme-mimics is here reviewed with a particular focus on the most recent achievements using different polymer formats such as microgels and nanogels, beads, membranes and also silica nanoparticles. 

Abstract. An overview of the synthesis and applications of microgels and coreshell particles is provided, with emphasis on work originating from the author s laboratory. Microgels, which are cross-linked polymer latex particles, can be used for selective uptake of ions or polymers, or the controlled release of various compounds. Various methods for the synthesis of core-shell particles are described such as interfacial polymerization, layer-by-layer deposition, colloidosomes , internal phase separation, and silica shells. The release kinetics for controlled (sustained or triggered) release purposes is discussed. 

The purpose of this article is to review the use of microgel particles and of core shell particles, primarily in the context of selective uptake and controlled release applications. Most of the examples will be taken from the work of the author and his coworkers in Bristol, carried out over many years of researching this topic. 

As well as sustained release, core/shell particles may be used also for triggered release applications. In this case, as with the microgel systems discussed earlier, an external trigger is used to cause some change in the properties of the shell polymer, which allows the active molecules to diffuse across the shell into the exterior. With many active materials there is an optimum dosage that is required in the exterior, e.g. with drugs. This... 

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