Interfacial polymerization research

Our research group has developed a multicatalyst system around an encapsulated amine catalyst (Kobaslija and McQuade 2006) that promotes nitroaUcene synthesis. Like the Royer catalysts, these microcapsules are based on a PEI shell. Unlike that system, however, templating is accomplished with a methanol in cyclohexane ( oil-in-oil ) emulsion in an interfacial polymerization, with the PEI cross-linked... 

The production by Loeb and Sourirajan of the first successful anisotropic membranes spawned numerous other techniques in which a microporous membrane is used as a support for a thin, dense separating layer. One of the most important of these was interfacial polymerization, an entirely new method of making anisotropic membranes developed by John Cadotte, then at North Star Research. Reverse osmosis membranes produced by this technique had dramatically improved salt rejections and water fluxes compared to those prepared by the Loeb-Souri-rajan process. Almost all reverse osmosis membranes are now made by the interfacial polymerization process, illustrated in Figure 3.20. In this method, an aqueous solution of a reactive prepolymer, such as a polyamine, is first deposited in the pores of a microporous support membrane, typically a polysul-fone ultrafiltration membrane. The amine-loaded support is then immersed in a water-immiscible solvent solution containing a reactant, such as a diacid chloride in hexane. The amine and acid chloride react at the interface of the two immiscible... 

Figure 3.20 Schematic of the interfacial polymerization process. The microporous film is first impregnated with an aqueous amine solution. The film is then treated with a multivalent crosslinking agent dissolved in a water-immiscible organic fluid, such as hexane or Freon-113. An extremely thin polymer film forms at the interface of the two solutions [47]. Reprinted from L.T. Rozelle, J.E. Cadotte, K.E. Cobian, and C.V. Knopp, Jr, Nonpolysaccharide Membranes for Reverse Osmosis NS-100 Membranes, in Reverse Osmosis and Synthetic Membranes, S. Sourirajan (ed.), National Research Council Canada, Ottawa, Canada (1977) by permission from NRC Research Press...

Other researchers (M19, V6, V7) encapsulated the drops of the sample by interfacial polymerization and then obtained the drop distribution by photomicrography. 

Radical polymerization can be carried out under homogenous as well as heterogenous conditions. This difference is classified based on whether the initial mixture and/or final product are homogenous or heterogenous. Some homogenous mixtures become heterogenous as polymerization proceeds as a result of insolubility of the resulting polymer in the reaction media. There are many other specialized processes that are used to synthesize materials via free-radical polymerization. These include interfacial polymerization, gas phase reactions ( popcorn polymerization ), as well as the use of specialized media like supercritical fluids. Current research efforts include the study of such... 

Researchers at GE and Bayer independently developed commercially feasible synthetic processes for BPA-PC in the 1950s and began commercial production in the early 1960s. Bayer was awarded the U.S. patent for PC produced via the interfacial polymerization process and GE the U.S. patent for the melt transesterification process. However, until recently, the major part of BPA-PC was produced via the interfacial process. Further information on the history of PC development can be found in previously published reviews. 

Since the 1960s, when the first supported Hquid membranes were proposed, many efforts have been made to overcome and improve the drawbacks associated to these membrane systems. Numerous researches deal with the stability of membranes by developing new techniques such as the geUed SLM or by adding a thin top-layer by interfacial polymerization... 

Yan, L. Jiang, J. Zhang, Y. Liu, J. Preparation and characterization of large-size halloysite nanotubes particles by a combined technique of interfacial polymerization and condensation polymerization. Journal of Nanoparticle Research (2011), 13(12), 6555-6561. 

Based on the membrane surface properties and the HA properties, various researchers have attempted to change the membrane surface characteristics by surface modification. Different techniques have been performed, such as ion beam irradiation, plasma treatment, redox-initiated graft polymerization, photochemical grafting, and interfacial polymerization (IP). In this chapter, two surface modification techniques, IP and photochemical grafting, are discussed by means of experimental examples. The surface characteristics of the unmodified membrane and the modified membranes are studied and their relationships with irreversible fouling and NF performance are reported. 

Many researchers have studied the interfacial science and technology of laminar flow in microfluidics [8]. Interfacial polymerization and the subsequent formation of solid micro structures, such as membranes and fibers in a laminar flow system, are very interesting techniques because the bottom-up method through polymerization is suitable for the formation of miniature structures in a microspace [3]. The development of such microstructure systems plays an important role for the integration of various microfluidic operations and microchemical processing [9]. For instance, membrane formation in a microchannel and further modification has a strong potential for useful functions such as microseparation, microreaction and biochemical analysis [8-10]. Here, we will introduce several reports on polyamide and protein membrane formation through interfadal polycondensation in a microflow. 

One of the more interesting fronts of development includes the search for improved membrane materials. While no new polymeric RO membranes have been introduced commercially over the last 20 to 30 years, there have been developments in performance (see Figure 1.5). These improvements in performance were achieved via modifications to the membrane itself (surface modifications made possible due to more advanced membrane characterization techniques) and closer tolerances in the interfacial polymerization reaction to make the membrane, and enhancements of the module design. Membranes with these improvements are commercially available today. While work is continuing with modifications to the current thin-film composite polyamide membranes, researchers are looking toward additional materials that might be suitable for use as RO membranes. 

An interesting group of composite membranes with very good properties is produced by condensation of furfuryl alcohol with sulfuric acid. The first membrane of this type was made by Cadotte at North Star Research and was known as the NS200 membrane [32], These membranes are not made by the interfacial composite process rather a polysulfone microporous support membrane is contacted first with an aqueous solution of furfuryl alcohol and then with sulfuric acid. The coated support is then heated to 140 °C. The furfuryl alcohol forms a polymerized, crosslinked layer on the polysulfone support the membrane is completely black. The chemistry of condensation and reaction is complex, but a possible polymerization scheme is shown in Figure 5.10. 

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