Nanocomposites capsules

New class of microobjects synthesized by Layer-by-Layer assembly method has been observed. These are polyelectrolyte nanocomposite microcapsnles. The influence of microenvironment parameters pH and ionic force of a solution, structure of solvent and temperature) on the physical and chemical properties of polyelectrolyte capsules has been described. The basic approaches to capsulation of organic substances, based on the change of microcapsule environment properties, the approaches to modification of microcapsule shells to give them sensitivity to external influences have been observed and analyzed. Usually the inorganic nanoparticles are used for such modification of microcontainers. During our work the basic methods of nanocomposite capsules fabrication were described and the ways of microcapsule shell permeability control by external influences, such as electromagnetic irradiation and ultrasound were considered. 

S.2.2 Synthesis of nanocomposite capsule shells by ionic-exchange reactions... 

Brayner, R., Helary, C., Livage, J. and Coradin, T. (2006) Turning biopolymer particles into hybrid capsules the example of silica/alginate nanocomposites. Journal of Materials Chemistry, 16, 1178-1182. 

In the case of the spherical nano-ohjects (Table 14.1), formed by 12 pentagonal (Mo)Mo5 units linked by 30 mono- or dinuclear linkers, there is, for each species, a nanoscaled capsule cavity and 20 size-tunable specific nanopores of the type M 0 (for example with n = 6 or 9), which can act as substrate specific receptors [8]. The cavity can even house smaller polyoxometalates, like different Keggin ions, to form a supramolecular nanocomposite of a unique kind (see Figure 14.10) [13]. Some typical interesting reactions are ... 

An attempt to use a recently patented concept (Dispersed Nano-Objects Protective Encapsulation—DOPE process) intended to disperse carbon nanotubes in polymeric matrices was reported. Physically cross-linked alginate capsules were successfully formed in the presence of either cellulose whiskers or microfibrillated cellulose [153]. The resulting capsules were extruded with a thermoplastic material. Another possible processing technique of nanocomposites using cellu-losic nanoparticles in the dry state present in the filtration of the aqueous suspension to obtain a film or dried mat of particles followed by immersion in a... 

The functions of the fourth hierarchical level are associated with capsulation of nanocomposites to maintain their properties and prolong the action of dmgs. Nanocapsulation is carried out with dextran, gelatin, polyvinyl alcohol, and polyvinyl pyrrolidone. 

Mohwald, H.D.E. and Sukhorukov, G.B., Smart Capsules, in Multilayer Thin Films, Sequential Assembly of Nanocomposite Materials, Decher, G. and Schlenoff, J.B., Eds., Wiley-VCH Verlag GmbH Co KgaA, Weinheim, 2002, pp. 363-392. 

Micrometer-sized hollow spheres with metal NPs (10-30 nm) were obtained by photoreduction of Ag in polyelectrolyte multilayers comprising Ag -PSS layers immobilized onto submicrometer-sized PS particles [138]. Hollow capsules with metal NPs can be formed either via a reduction of Ag followed by a core dissolution or by a core dissolution with a subsequent reduction of Ag. The formed spherical nanocomposites with silver NPs were stable for long time (over 3 months). The silver-based core-shell particles and hollow spheres may find interesting applications in catalysis and molecular photoprinting. The PEI-Pd ... 

An example of a nanocomposite with an additional function in the material is self-healing systems. Capsule-based systems that have the healing agents included in cavities in the polymer matrix are one type of self-healing materials. 

In these systems capsules are broken upon damage and reactive monomers that are able to close the scratch fill the break. Another possibility is the function of the polymers that show reversible bond breakage and formation. Examples are groups that can undergo Diels-Alder reactions such as maleimide and furan rests. Sol-gel-derived sihca particles that contain these groups can be used for the preparation of self-healing nanocomposites [56]. 

Ridi, F., Bonini, M., Baghoni, R, 2014. Magneto-responsive nanocomposites preparation and integration of magnetic nanoparticles into films, capsules, and gels. Adv. Colloid Interface Sci. 207, 3-13. 

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