In-situ miniemulsion polymerization

Ham HT, Choi YS, Chee MG, et al. (2006) Singlewall carbon nanotubes covered with polystyrene nanopairides by in-situ miniemulsion polymerization. J Polym Sd Part A Polym Chem 44 573-584... 

Lopez-Martinez El, Marquez-Lucero A, Hemandez-Escobar CA, et al. (2007) Incorporation of silver/carbon nemoparticles into poly(methyl methacrylate) via in situ miniemulsion polymerization and its influence on the glass-transition temperature. J Polym Sci Part B Polym Phys 45 511-518... 

The influence of surfactant concentration on particle size and stability of nanocapsules with liquid cores, synthesized by an in-situ miniemulsion polymerization process, was investigated by van Zyl et al. [74]. 

The preparation of PCNs by means of in situ miniemulsion polymerization is not an easy task, since clay can interact with all components in the system (monomer, surfactant, hydrophobe), thus influencing the droplet size distribution after the miniemulsification step and also the polymerization loci. As... 

Synthesis of polymer microspheres in the presence of magnetic nanoparticles, such as suspension polymerization or its modified versions, dispersion polymerization, surface-initiated radical polymerization, acid-catalyzed condensation polymerization, emulsion polymerization, mini-/microemulsion polymerization, in situ oxidative polymerization, inverse emulsion cross-linking, emulsion/double emulsion-solvent evaporation, and supercritical fluid extraction of o/w miniemulsion... 

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... 

The use of RAFT to control miniemulsion polymerization has also been reported. " We showed that RAFT in miniemulsion can be used to produce narrow dispersity polystyrene in a batch process. Some retardation is observed with dithiobenzoate RAFT agents.However, this is markedly reduced when aliphatic dithioesters " or trithiocarbonate RAFT agents are used. One of the issues with traditional miniemulsion polymerization is the high level of surfactant and co-stabilizer that is typically employed. Pham et have described surfactant-free miniemulsion polymerization. As with the emulsion procedure referred to above, amphipathic macro-RAFT agents synthesized in situ by polymerization of AA were used as the sole stabilizers. This process eliminated secondary nucleation of new particles and leads to a latex with no mobile surfactant and good particle size control. 

Various initiation strategies and surfactant/cosurfactant systems have been used. Early work involved in situ alkoxyamine formation with either oil soluble (BPO) or water soluble initiators (persulfate) and traditional surfactant and hydrophobic cosurfactants. Later work established that preformed polymer could perform the role of the cosurfactant and surfactant-free systems with persulfate initiation were also developed, l90 222,2i3 Oil soluble (PS capped with TEMPO,221 111,224 PBA capped with 89) and water soluble alkoxyamines (110, sodium salt""4) have also been used as initiators. Addition of ascorbic acid, which reduces the nitroxide which exits the particles to the corresponding hydroxylamine, gave enhanced rates and improved conversions in miniemulsion polymerization with TEMPO.225 Ascorbic acid is localized in the aqueous phase by solubility. 

In situ polymerization reactions are performed in an emulsion system where an organic solution of the monomer (bearing, e.g., vinylic or acrylic moieties) is the dispersed phase and an aqueous solution containing a surfactant is the continuous phase. Methyl methacrylate has been used for the preparation of quercetin-loaded nanoparticles in a miniemulsion systum. Quercetin was shown to slower the polymerization reaction, but this effect could be attenuated by the addition of ascorbic acid. 

When conducting the ROMP of norbornene or cyclooctadiene in miniemulsions [82], two approaches were followed (i) addition of a catalyst solution to a miniemulsion of the monomer and (ii) addition of the monomer to a miniemulsion of Grubbs catalyst in water. With the first approach it was possible to synthesize stable latexes with a high conversion, whereas for the second approach particles of >400 nm were created, without coagulum, but with 100% conversion. Subsequently, a water-soluble ruthenium carbene complex [poly(ethylene oxide)-based catalyst] was prepared and used in the direct miniemulsion ROMP of norbornene [83], whereby particles of 200-250 nm were produced. The catalytic polymerization of norbornene in direct miniemulsion was also carried out in the presence of an oil-soluble catalyst generated in situ, or with a water-soluble catalyst [84] the reaction was faster when using the oil-soluble catalyst. Helical-substituted polyacetylene could be efficiently polymerized in direct miniemulsion to yield a latex with particles that ranged between 60 and 400 nm in size, and which displayed an intense circular dichroism [85] that increased as the particle size decreased. The films were prepared from dried miniemulsion latexes that had been mixed with poly(vinyl alcohol) (PVA) in order to conserve the optical activity. 

Of further interest is the in-situ synthesis of amphiphilic block copolymers via a miniemulsion route that allows access to surfactant-free miniemulsion systems. This can be readily achieved by utilizing an initial polymer synthesized by CRP techniques and miniemulsion polymerization as a macroinitiator for chain extension. This was shown by Charleux and coworkers to allow for the synthesis of stimuli-responsive particles by the introduction of a water-soluble monomer (A, A -diethylacrylamide) that exhibits a lower critical solution temperature (LCST) at about 32 °C (Delaittre et al, 2007). 

The first example of the use of CRP in miniemulsion to produce nanocapsules was reported by van Zyl et al. [35], who employed a RAFT agent for the ab initio miniemulsion polymerization of styrene. It is important to note that, in this example, the dispersed phase was stabilized by a traditional surfactant (rather than a CRP polymer), with the CRP polymer generated in situ in the continuous phase before... 

Recently, functionalized latexes have been obtained by means of CRP in an ab initio batch emulsion and miniemulsion polymerization process. Even though these woiks may not always intentionally be making surface-functional particles, it is a very efficient way of doing so. The approach consists in adding a hydrophilic and water-soluble control agent and in situ building up a polymeric surfactant, which after micellization causes the control agent to be inside the latex particle. 

Furthermore, this approach was also translated very effectively to nitroxide-mediated emulsion and miniemulsion polymerization [73-76] to prepare in situ PAA-based hairy nanoparticles using a water-soluble alkoxyamine initiator. 

Shork et al. have shown that incorporation of polyester into each acrylic latex particle, prepared via miniemulsion polymerization, leads to an effective in situ grafting of the acrylic and polyester systems [59], The hydrophobic nature of the polyester resin makes it impossible to be accommodated by traditional emulsion polymerization due to mass-transfer bmitations in crossing the aqueous phase to micellar nu-cleation sites. Thus, stable water-based latex coatings can be prepared that also have the ability to cure (by crosshnking).The above hybrid miniemulsion polymerization was successfiiUy used to incorporate an oil modified polyurethane in the acryKc... 

Many synthesis methods for nanopartides of these materials and thdr surface functionalization have been devdoped. Nanocomposites based on polyolefins were prepared by mdt compounding with nanoscaled ZnO and 1102. Amphiphilic copolymers and surfadants were used to stabilize pattides for film casting in polystyrene, " polycarbonate, and PMMA. By in situ partide preparation in MeOH and subsequent mixing with acetone and PMMA for solvent evaporation transparent ZnO/PMMA films could be realized even without further surface modification. Poly(acrylic add-co-sodium aaylate)/ZnO composite latex partides were obtained via inverse miniemulsion polymerization. ... 

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