Polymeric membranes microparticles

Numerous synthetic or natural polymers have been used as matrices for micro- and nanoparticles or -capsules, most of which are biodegradable or bioerodible. Microparticles (or microspheres) are systems in which the drug is dispersed throughout the particle whereas capsules are vesicular systems in which the drug is contained in a cavity surrounded by the polymeric membrane (Couvreur and Puisieux, 1993). 

Besides the synthesis of bulk polymers, microreactor technology is also used for more specialized polymerization applications such as the formation of polymer membranes or particles [119, 141-146] Bouqey et al. [142] synthesized monodisperse and size-controlled polymer particles from emulsions polymerization under UV irradiation in a microfluidic system. By incorporating a functional comonomer, polymer microparticles bearing reactive groups on their surface were obtained, which could be linked together to form polymer beads necklaces. The ability to confine and position the boundary between immiscible liquids inside microchannels was utilized by Beebe and coworkers [145] and Kitamori and coworkers [146] for the fabrication of semipermeable polyamide membranes in a microfluidic chip via interfacial polycondensation. 

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. 

Both W/O/W and O/W/O emulsions have attracted considerable attention because of their potential applications in food science [4-7], cosmetics [8-10] and pharmaceutics [11]. In particular, there have been many studies on the pharmaceutical applications of W/O/W emulsions because the internal aqueous droplets can contain water-soluble drugs for controlled release or targetable delivery [12-14]. Solid microcapsules loaded vhth bioactive polymers are also prepared from W/O/W droplets by the solvent evaporation method [15-18]. Other applications studied thus far include the synthesis of shaped polymeric microparticles [19] and the use of the intermediating phase as the permeation membrane in separation technology [20-25]. 

Table 6.6 lists microparticles manufactured through double-emulsion routes by membrane and microfluidic devices. It can be seen that the methods afford the production of a variety of products by means of sequential secondary reactions/processes in the double-emulsion droplets, such as polymerization, gelation, evaporation, freeze-drying, and crystallization. 

Membrane and microfiuidic devices have also been adopted for the precision manufacture of solids from double-emulsion templates. To date, several different types of particles have been successfully produced by incorporating use of various membrane and microfiuidic devices in processes of polymerization, gel formation, crystallization, and molecular or particle self-assembly. Membrane emulsification is more suited to the fabrication of less sophisticated particulates, such as solid lipid micro-Znanoparticles, gel microbeads, coherent polymeric microspheres, and inorganic particles such as silica microparticles. Microfiuidic devices allow more sophisticated particle designs to be created, such as colloidosomes, polymerosomes, 3D colloidal assemblies, asymmetric vesicles, core-shell polymer particles, and bichromal particles. 

Solid porous materials can be prepared by polymerization of all three types (o/w, w/o, and bicontinuous middle phase) of microemulsions [71]. Gupta and Singh [34] obtained porous polymers by polymerization of styrene/divinylbenzene as the continuous phase in an oil-continuous (w/o) microemulsion. Which was prepared using AOT as surfactant. The polymerization was carried out thermally at 70 °C using benzoyl peroxide as initiator. The porous materials may eventually be transformed into porous membranes. Such membranes have many applications in the field of separation science, composites, medicines, and biotechnology. Depending on the pore size, the porous polymers could be used for the separation of dust as also microparticles such as virus, bacteria, pigments, colloidal particles, etc. 

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