Polymer capsules

A unique feature of in situ encapsulation technology is that polymerization occurs ia the aqueous phase thereby produciag a condensation product that deposits on the surface of the dispersed core material where polymerization continues. This ultimately produces a water-iasoluble, highly cross-linked polymer capsule shell. The polymerization chemistry occurs entirely on the aqueous phase side of the iaterface, so reactive agents do not have to be dissolved ia the core material. The process has been commercialized and produces a range of commercial capsules. 

Hollow and porous polymer capsules of micrometer size have been fabricated by using emulsion polymerization or through interfacial polymerization strategies [79,83-84, 88-90], Micron-size, hollow cross-linked polymer capsules were prepared by suspension polymerization of emulsion droplets with polystyrene dissolved in an aqueous solution of poly(vinyl alcohol) [88], while latex capsules with a multihollow structure were processed by seeded emulsion polymerization [89], Ceramic hollow capsules have also been prepared by emulsion/phase-separation procedures [14,91-96] For example, hollow silica capsules with diameters of 1-100 micrometers were obtained by interfacial reactions conducted in oil/water emulsions [91],... 

The foregoing examples show that hollow polymer capsules with varying composition and sizes of ca. 2-20 micrometers can be produced, either by templating charged (latex particles and biocrystals) or uncharged (organic microcrystals), and that different core removal procedures can be employed. Nanometer-size polymer capsules have also been produced by employing smaller particle templates [107]. 

FIG. 9 Confocal laser scanning micrograph of a hollow polymer capsule. The polymer capsule was obtained from polymer multilayer-templated FDA microcrystals after removal of the colloidal core. The FDA microcrystals were coated with SDS and 11 polyelectrolyte layers [(PAH/PSS)3/PAH/ (PSS/PAH-FITC)2]. (PAH-FITC = PAH labeled with fluorescein isothiocyanate.) The microcrystal core was removed by exposure of the coated microcrystals to ethanol, causing solubilization of FDA. 

FIG. 13 TEM micrograph of a hollow composite nanoparticle/polymer capsule dried on a carbon grid. The hollow composite capsule was obtained after removal of the ME core from Si02/PDAD-MAC-coated ME particles by treatment with hydrochloric acid. The shadowing seen is a result of collapse and overlapping of the hollow capsule upon drying. (From Ref. 110.)... 

K Ishihara, K Matsui. Glucose-responsive insulin release from polymer capsule. J Polym Sci 24 413-417, 1986. 

Marinakos SM, Anderson MF, Ryan JA, Martin LD, Feldheim DL. Encapsulation, permeability, and cellular uptake characteristics of hollow nanometer-sized conductive polymer capsules. J Phys Chem B 2001 105 8872-8876. 

Marinakos SM, Novak JP, Brousseau LC, House AB, Edeki EM, Feldhaus JC, Feldheim DL. Gold particles as templates for the synthesis of hollow polymer capsules. Control of capsule dimensions and guest encapsulation. J Am Chem Soc 1999 121 8518-8522. 

Fig. 3 Synthesis of nanometer-sized hoUow polymer capsules from polymer-coated Au-particles...

Fig. 16. Concept of glucose sensitive insulin release system using PVA/poly (NVP-10-PBA) complex system, (polymer capsule type)...

The first heterogeneous osmium catalyst applicable for asymmetric dihydroxylation reactions was described by Kobayashi and coworkers (Table 9, entry 1) [38, 39]. Osmium tetroxide was enveloped in a polymer capsule by microencapsulation techniques [40,41]. The asymmetric dihydroxylation of transmethylstyrene with poly(acrylonitrile-co-butadiene-co-styrene) microencapsulated (ABS-MC) osmium tetroxide as catalyst, NMO as the cooxidant, and (DHQD)2PHAL as the chiral ligand completed in 88% yield with 94% ee [38]. The catalyst and the chiral ligand were reused in five consecutive runs without loss of activity. However, the use of NMO as cooxidant required the slow... 

Figure 7.10. Sectioning of a TEM sample using an ultramicrotome instrument. Shown is an ultramicrotome instrument with a built-in nitrogen cryogenic system, used to section samples with a thickness of 25 nm-5 mm.h7l Also shown is a TEM image of polymer capsules that have been sectioned using an ultramicrotome instrument. Image reproduced with permission from Dai, Z. Mohwald, H. Langmuir 2002,18, 9533. Copyright 2002 American Chemical Society.

Polymer capsules Core-shell Flavour composition entrapped in capsule consisting of solvent core covered by protein shell Dry product or liquid dispersion Limited (oxidative) stability of encapsulated flavour Flavour can be loaded in empty particles Flexible particle size Relatively slow release/burst-like release... 

Fontaine PP. Utilizing polymer capsules as a biological delivery system for administering potential ribozyme drugs. 223rd ACS National Meeting, Orlando, FL, 2002. 

Thus polymer capsules will remain in the tissue for varying lengths of time after completion of therapy. 

INORGANIC PARTICLES FORMATION IN NANOENGINEERED POLYMER CAPSULES... 

Hollow polymer capsules (or microcapsules) filled by inhibitor vapors are intended for fighting corrosion in oil and gas wells. Capsules are pumped... 

Fig. 23 (a) Formation of polymer capsules by polymer nanoprecipitation on preformed miniemulsion droplets Examples for capsule formation by nanoprecipitation with (b) polymethylacrylate (PMA) and (c) PMMA [193,194]... 

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