Polymerization in miniemulsion

Polymerization in miniemulsion is a very suitable technique to avoid this problem since each droplet acts as a nanoreactor. As a result, pure polyacrylonitrile (PAN) nanoparticles were obtained in the size range 100 nmwater phase. This is no restriction for a miniemulsion polymerization process, and the use of a hydro-phobic initiator 2,2 azobis(2-methylbutyronitrile) allows the preservation of the droplets as the reaction sites by droplet nucleation (see Fig. 12). Initiation of the... 

Living radical polymerizations in miniemulsions have also been conducted by de Brouwer et al. using reversible addition-fragmentation chain transfer (RAFT) and nonionic surfactants [98]. The polydispersity index was usually below 1.2. The living character is further exemplified by its transformation into block copolymers. 

The polymerization in miniemulsion can also be performed in the presence of an oil, which is inert to the polymerization process. During polymerization, oil and polymer can demix, and many different structures such as an oil droplet encapsulated by a polymer shell, sponge like architectures, or dotted oil droplets can be formed. The formation of such structures is known from classical emul-... 

Switching from the very hydrophilic clays towards other inorganic nanoparticles, e.g., colloidal silica, leads, in the interplay with polymerization in miniemulsions, into a potential structural complexity, which covers the whole range from embedded particles (such as in the case of the calcium carbonate and carbon blacks) to surface bound inorganic layers (such as in the case of the clays). For basic research they are ideal systems to analyze complex structure formation processes in emulsions, since the original droplet shows a structure which is essentially established by molecular forces and local energy considerations, and which is ideally just solidified into a polymer structure. 

Musyanovych A, Landfester K (2008) Synthesis of poly(butylcyanoacrylate) nanocapsules by interfacial polymerization in miniemulsions for the delivery of DNA molecules. Prog Colloid Polym Sd 134 120-127... 

Cunningham and coworkers [65-68] have completed detailed modeling of nitroxide mediated radical polymerization in miniemulsion. They found that issues of distribution of the control agent between the aqueous and organic phases can be critical to maintaining livingness. 

ATRP polymerization in miniemulsion has recently attracted more attention and met with greater success. Some difficulties with conventional initiation were attributed to catalyst oxidation during the homogenization/sonication step particularly when more active, less oxidatively stable, catalysts are used. This problem was solved using reverse ATRP or combinations of reverse and normal A I RP " that meant the catalyst could be added in its oxidized form (Section... 

The Rp curves of miniemulsion and conventional emulsion polymerization obtained by calorimetry show the same general behavior [219]. In contrast to conventional emulsion polymerization, in miniemulsion polymerization, the monomer concentration in polymer particles diminishes throughout the polymerization. At the beginning, the nucleation rate overcompensates the decrease of monomer concentration leading to the first rise in the Rp. The number of droplets decreases and the remaining droplets shrink in size due to monomer loss by molecular diffusion to the polymer particles. As a consequence, the nucleation rate diminishes and eventually it may not be fast enough to compensate the decrease of the monomer concentration. Thus, Rp may reach a maximum and decrease before the end of the nucleation period [219], In conventional emulsion polymerization, the nucleation period ends before the first maximum in Rp, which is ascribed to the disappearance of monomer droplets [125]. 

Although it may seem obvious, the definition of miniemulsion polymerizatim can vary depending on the objectives of the specific research programme. In its narrowest sense, miniemulsion polymerization could be defined as the polymerization of all the monomer droplets present in the initial emulsion, where the final particle size distribution is reflected in the initial droplet size distribution (i.e. there is a one-to-one correspondence between the droplets and particles). It quickly became evident that this definition was too narrow to accommodate most (if not all) of the reactions termed miniemulsion polymerization because there was no such correspondence. Typically, fewer particles were found than the original number of monomer droplets. The definition, therefore, could be taken as the polymerization in miniemulsion droplets where not all the droplets succeed in becoming polymer particles. This definition only allows for nucleation in monomer droplets. 

Musyanovych A, Landfester K (2008) Synthesis of poly(butylcyanoacrylate) nanocapsules by interfacial polymerization in miniemulsions for the delivery of DNA molecules. In Auemhammer GK, Butt H-J, Vollmer D (eds). Surface and interfacial forces - from fundamentals to applications. Progress in colloid and polymer science, vol 134. Springer, Berlin, Heidelberg, pp 120-127... 

Esteves ACC, Barros-Timmons A, Monteiro T et al (2005) Polymer encapsulation of CdE (E = S, Se) quantum dot ensembles via in-situ radical polymerization in miniemulsion. J Nanosci Nanotechnol 5 766-771... 

RAFT polymerization in miniemulsion has been carried out in a tubular reactor. Emulsion is prepared in a batch reactor using sodium dodecyl sulfate (SDS, surfactant), Triton X-405 (surfactant), styrene (monomer), hexadecane... 

Russum JP, Jones CW, SchorkFJ (2004) Continuous reversible addition-fragmentation chain transfer polymerization in miniemulsion utilizing a multi-tube reaction system. Macromol Rapid Commun 25 1064—1068... 

Russum JP, Jones CW, Schork FJ (2005) Continuous living polymerization in miniemulsion using reversible addition fragmentation chain transfer (RAFT) in a mbular reactor. Ind Eng Chem Res 44 2484-2493... 

Figure 15.4 Chemical structures of surfmers for radical polymerization in miniemulsion.

Controlled radical polymerization techniques are suitable for synthesizing polymers with a high level of architectural control. Notably, they not only allow a copolymerization with functional monomers (as shown previously for free-radical polymerization), but also a simple functionalization of the chain end by the initiator. Miniemulsion systems were found suitable for conducting controlled radical polymerizations [58-61], including atom transfer radical polymerization (ATRP), RAFT, degenerative iodine transfer [58], and nitroxide-mediated polymerization (NMP). Recently, the details of ATRP in miniemulsion were described in several reviews [62, 63], while the kinetics of RAFT polymerization in miniemulsion was discussed by Tobita [64]. Consequently, no detailed descriptions of the process wiU be provided at this point. 

Ionic polymerizations in heterophase systems have been described very rarely, and are generally considered as unconventional. Nonetheless, the conditions employed for ionic polymerizations in miniemulsions are ideal, as there is no diffusion of the monomers. Ionic miniemulsion polymerizations have been carried out either under mild conditions (e.g., in the presence of water) or in water-free... 

Figure 15.5 Examples of monomers for ionic polymerizations in miniemulsion.

M. F. Cunningham, Recent progress in nitroxide mediated polymerizations in miniemulsions, C. R. Chim. 2004, 6, 1351-1374. 

No.25, 12th Dec.2000, p.9239-46 LIVING RADICAL POLYMERIZATION IN MINIEMULSION USING REVERSIBLE ADDITION-FRAGMENTATION CHAIN TRANSFER... 

From a mathematical point of view, limiting cases of macroemulsion polymerization are mini- and microemulsion polymerizations. In miniemulsion polymerization, only small monomer droplets are present and these are also the main reaction locus. In microemulsion polymerization, the monomer droplets are also small and, in principle, reaction can take place in the monomer droplets as well as in the micelles and polymer particles. An important feature of a microemulsion is that it is thermodynamically stable, whereas the other emulsion types are only kinetically stable. However, if monomer is added very slowly and a small amount of surfactant is present, polymer particles gradually swell starting from a micelle population only. Thus, the emulsion polymerizations differ with respect to the populations present, but in all cases the latex obtained consists of segregated entities with a size at least one order of magnitude smaller than in suspension polymerization. In the most... 

Baier MC, Huber J, Mecking S (2009) Fluorescent conjugated polymer nanoparticles by polymerization in miniemulsion. J Am Oiem Soc 131 14267-14273... 

Synthesis of Poly(butylcyanoaciylate) Nanocapsules by Interfacial Polymerization in Miniemulsions for the Deiiveiy of DNA Moiecuies... 

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