Microencapsulation interfacial polymerization

The second general method, IMPR, for the preparation of polymer supported metal catalysts is much less popular. In spite of this, microencapsulation of palladium in a polyurea matrix, generated by interfacial polymerization of isocyanate oligomers in the presence of palladium acetate [128], proved to be very effective in the production of the EnCat catalysts (Scheme 3). In this case, the formation of the polymer matrix implies only hydrolysis-condensation processes, and is therefore much more compatible with the presence of a transition metal compound. That is why palladium(II) survives the microencapsulation reaction... 

Interfacial polymerization processes, in microencapsulation, 16 445 446 Interfacial tension, 24 134 in polymer blends, 20 323, 333 of fats and oils, 10 822 Interference, as cause of color, 7 326t, 339-340... 

Scher HB, Rodson M, Lee KS. Microencapsulation of pesticides by interfacial polymerization utilizing isocyanate or aminoplast chemistry. Pest Sci 1998 54 394-400. 

Saihi, D., Vroman, I., Giraud, S., and Bourbigot, S. 2006. Microencapsulation of ammonium phosphate with a polyurethane shell—Part II Interfacial polymerization technique. React. Funct. Polym. 66 1118-1125. 

Two types of microencapsulation are known in the art based upon the shellwall forming chemistry. These are interfacial polymerization and in-situ polymerization. Encapsulating plastic shellwalls are synthesized at the 0/W (Oil-in-Water) interface of a pesticide emulsion by reacting oil-soluble monomers dissolved in the pesticide with water-soluble monomers added to the emulsion. This process is referred to as interfacial polymerization. 

Alilla A and Kas HS. Microencapsulation technology Interfacial polymerization method. In Wise DL, ed. Handbook of Pharmaceutical Controlled Release Technology. New York, Basel Marcel Dekker, 2000, pp. 271-285. 

Whateley, T.L. Microcapsules preparation by interfacial polymerization and interfacial complexation and their application. In Microencapsulation Methods and Industrial Applications Benita, S., Ed. Dekker New York, U.S.A., 1996 Vol. 73, 349-375. 

Lee outlines three different physical methods that are commonly utilized for enzyme immobilization. Enzymes can be adsorbed physically onto a surface-active adsorbent, and adsorption is the simplest and easiest method. They can also be entrapped within a cross-linked polymer matrix. Even though the enzyme is not chemically modified during such entrapment, the enzyme can become deactivated during gel formation and enzyme leakage can be problematic. The microencapsulation technique immobilizes the enzyme within semipermeable membrane microcapsules by interfacial polymerization. All of these methods for immobilization facilitate the reuse of high-value enzymes, but they can also introduce external and internal mass-transfer resistances that must be accounted for in design and economic considerations. 

A variety of methods have been reported for producing microspheres including phase separation by polymer/polymer incompatibility and coacerva-tion [81] solvent evaporation or solvent removal [82] hot-melt microencapsulation spray drying interfacial polymerization and supercritical fluidprocessing teehniques (such as the gas antisolvent spray precipitation process [83] or rapid expansion of supercritical fluids [84]). The characteristics of the most important of these methods have been reviewed [85, 86]. 

Microencapsulation by interfacial polymerization with 1,6-diaminohexane and sebacoyl chloride Active immobilized enzyme investigation of optimal conditions for microencapsulation 816... 

Polymerization plays a key role in chemical microencapsulation. The basic mechanism of this method is to put a polymer wall (can be multilayer) through polymerization on a core material, which is in a form of small liquid droplets, solid particles, or even gas bubbles or to embed the core material in a polymer matrix through polymerization. Interfacial polymerization is one of the most important methods that have been extensively developed and industrialized for microencapsulation. According to Thies and Salaun, interfacial polymerization includes live types of processes represented by the methods of emulsion polymerization, suspension polymerization, dispersion polymerization, interfacial polycondensation/polyaddition, and in situ polymerization. This chapter is only focnsed on interfacial polycondensation and polyaddition in a narrow sense of interfacial polymerization. 

Salaun, F. Microencapsulation by interfacial polymerization. Encapsulation Nanotechnologies, Mittal, V., Ed., Hoboken, NJ John Wiley Sons, 2013, pp. 137-173. 

Salauen, F. Bedek, G. Devaux, E. Dupont, D. Gengembre, L. Microencapsulation of a cooling agent by interfacial polymerization Influence of the parameters of encapsulation on poly(urethane-urea) microparticles characteristics. Journal of Membrane Science (2011), 370(1-2), 23-33. 

Choi, K. Y. Min, K. S. Chang, T Microencapsulation of pesticides by interfacial polymerization. 2. Polyamide microcapsnles containing water-soluble drug. Polymer (1991), 15(5), 548-55. 

Cho, J.-S. Kwon, A. Cho, C.-G. Microencapsulation of octadecane as aphase-change material by interfacial polymerization in an emulsion system. Colloid and Polymer Science (2002), 280(3), 260—266. 

Periyasamy, S. Palanikkumaran, M. Agrawal, A. K. Kotresh, T. M. Microencapsulation of N-octadecane using interfacial polymerization. Jassal, M. Agrawal, A. K., Eds., From Emerging Trends in Polymers and Textiles, Proceedings of [the] International Conference, New Delhi, India, January... 

Some examples of microencapsulated EO are those reported by Scarfato et al. (2007), in which the polyurea microcapsules containing the EO of lemon bahn, lavender, sage, and thyme with anti-germinative activity were prepared by interfacial polymerization in 0/W annlsion. 

One may list a large number of surface chemical phenomena that are crucial in the preparation of more complex systems such as multiple emulsions and microcapsules. In the first case, the formulation is a complex system of an emulsion in an emulsion , with the most common being a water-in-oil-in-water (W/O/W) multiple emulsion, which requires the preparation of a stable W/O emulsion that is further emulsified into an aqueous solution of another surfactant to produce the final system. Microencapsulation is a process whereby the active ingredient is surrounded by a polymer shell that allows the controlled and slow release of the active. The most common procedure for encapsulation is interfacial polymerization, whereby two monomers are allowed to react at the interface (by condensation) to produce the... 

Emulsions are involved when interfacial polymerization is used to microencapsulate a lipophilic drug. In this case the drug is placed in an oil phase together with a hydrophobic monomer, an added surfactant and suitable mechanical shear allows these to be incorporated into the dispersed oil droplets of an O/W emulsion. A hydrophilic monomer is then dissolved in the aqueous phase and the two monomers interact at the oil/aqueous interface to create polymer films that form the capsule walls. For a hydrophilic drug all of the above could simply be reversed. 

Figure 5.4 Principle of insecticide microencapsulation by interfacial polymerization [28].

Agrochomicals. The microencapsulation of pesticides, herbicides, and other pest control agents has been an active area of development. Several books or book chapters (69-72) summarize much of these efforts. Wilkins (69, pp. 314-315) and Tsuji (71) list commercial microencapsulated formulations of pest control agents available in 1990 and 1999, respectively. Most of the microcapsules in these formulations are prepared by interfacial polymerization. 

Several encapsulated herbicide formulations exist. Encapsulated alachlor herbicide has been sold as a liquid or dry granule formulation. The capsules, produced by interfacial polymerization, are spherical with a diameter of 2-15 /um. Two thiocarbamate herbicides, EPTC and vemolate [1929-77-7], were encapsulated by interfacial polymerization because they are volatile compounds. When applied in imencapsulated form, they must be incorporated in the soil within 2 h in order to provide effective weed control. When applied as a microencapsulated formulation, the rate of volatilization is lower and soil incorporation can be... 

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