Soap-free emulsion polymerization

2 Fabrication of PMMA Nanocomposites Through Soap-free Emulsion Polymerization 

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Suspension polymerization may be the most important particle-forming polymerization from an industrial viewpoint. The system is very simple, composed of monomer, initiator, stabilizer, and medium (water in most cases). The monomer droplets with dissolving initiator are dispersed in water and the stabilizer exists at the interface. But suspension polymerization is regarded as a kind of homogeneous polymerization because the polymerization occurs only in monomer droplets and water does not affect the polymerization. Water contributes only to dividing the polymerization locus into small droplets and absorbing the heat evolved by polymerization. On the contrary, in emulsion polymerization, which is another type of polymerization performed in water and as practically important as suspension polymerization, water affects the polymerization significantly. In this section, emulsion polymerization is first discussed, and then some modified emulsion polymerizations such as soap-free emulsion polymerization and micro and mini emulsion polymerizations are described. 

Soap-free) emulsion Polymerization lispersion polymerization ... 

Ail microspheres were prepared using soap-free emulsion polymerization. Carboxylated microspheres were prepared by batch copolymerization. Batch copolymerization was performed with main monomer, S, lwt% of co-monomer, MAA, and 0.4wt% of initiator, KPS. All weight fractions were based on the amount of main monomer, S. These microspheres were named CM-1 for low carboxylated PS/PMAA, respectively. 

Polymer microspheres with monodispersed distribution in size are much perferable for phagocytosis assays, because the size dominantly governs phagocytosis of the microspheres by M< ). In addition, the microspheres should be prepared without any surfactants to exclude the influence of the soap molecules adsorbed onto the surface, on phagocytosis of the microspheres. We have synthesized monodispersed polystyrene microspheres by soap-free emulsion polymerization of styrene at 70 °C for 30 hr using potassium persulfate as a initiator [14]. The widely different diameters of the... 

Muller and coworkers prepared disc-like polymer Janus particles from assembled films of the triblock copolymer SBM and, after hydrolysis of the ester groups into methacrylic acid units, used these as Pickering stabilizer in the soap-free emulsion polymerization of styrene and butyl acrylate [111]. Armes and coworkers described the synthesis of PMMA/siUca nanocomposite particles in aqueous alcoholic media using silica nanoparticles as stabilizer [112], extending this method to operate in water with a glycerol-modified silica sol [113, 114]. Sacanna showed that methacryloxypropyltrimethoxysilane [115] in the presence of nanosized silica led to spontaneous emulsification in water, which upon a two-step polymerization procedure afforded armored particles with an outer shell of PMMA [116]. Bon and coworkers demonstrated the preparation of armored hybrid polymer latex particles via emulsion polymerization of methyl methacrylate and ethyl methacrylate stabilized by unmodified silica nanoparticles (Ludox TM O) [117]. Performance of an additional conventional seeded emulsion polymerization step provided a straightforward route to more complex multilayered nanocomposite polymer colloids (see Fig. 14). 

Yu C-L, Kang J-S, Zhang F-A (2009) The effect of nano-Si02 coUoid on soap-free emulsion polymerization of methyl methacrylate and hydroxyethyl methacrylate. J Macromol Sci A Pure Appl Chem 46(9) 870-875... 

A similar strategy involving Laponite or MMT platelets grafted with polymerizable organotitanate and organosilane molecules was recently reported by Voorn et al. [285, 286]. Here, starved-feed soap-free emulsion polymerization of MMA conducted in the presence of the organoclay led to clay encapsulation. However the solid content was quite low (typically around 7%). 

Fig. 33 Left Synthesis of ciay-armored PMMA latexes through soap-free emulsion polymerization using PDMAEMA-tethered clay as stabiUzen Right TEM image of the so-obtained PMM A/clay composite coUoid. Reproduced from [290] with permission of Wiley Periodicals...

In a quest for different applications various numbers of polymers have been chosen to prepare encapsulated and functionalized magnetic particles by soap-free emulsion polymerization. Examples are amide- and carboxyl-functionalized magnetic latex for protein immobilization [156], and thermally sensitive and carboxyl-functionalized particles for antibody purification [157], bioprocesses... 

Fig. 17 (a) Magnetic latex preparation by soap-free emulsion polymerization, (b) TEM of magnetic polymer particles. Reprinted from [153] with permission... 

Recipe, monomer conversion, particles size and particles number for a series of soap-free emulsion polymerizations of styrene in the presence of macromonomer and increasing concentrations of taponite. 

C.F. Lee, W.Y. Chiu, Soap-free emulsion polymerization of methyl methacrylate in the presence of CaSO, Polym. Int. 1993, 30, 475-481. 

L. Z. Qiu and B. J. Qu, Preparation and characterization of surfactant-free polystyrene/layered double hydroxide exfoliated nanocomposite via soap-free emulsion polymerization. Journal of Colloid and Interface Science, 301 (2006), 347-51. 

K. Nakabayashi, M. Kojima, S. Inagi, Y. Hirai, M. Atobe, Size-controlled synthesis of polymer nanoparticles with tandem acoustic emulsification followed by soap-free emulsion polymerization. ACS Macro Lett. 2, 482-484 (2013)... 

Pig. 2 Scanning electron microscopy images of polystyrene colloids obtained by soap-free emulsion polymerization, taken after a 1.75 h, b 4.5 h, c 7 h, d and after 24 h. Scale bar 1 p.m. Insets Images at higher magnification, e Growth of polystyrene colloids during emulsion polymerization. Experimental conditions ammonium persulfate 0.11 g acrylic add 0.15 g sodium chloride 0.2 g milli-Q water 300 ml styrene 25 g divinylbenzene 0.25 g. [34]... 

Fig. 38 Schematic illustrations of proposed mechtmisms for encapsulation by soap-free emulsion polymerization with poly(St-co-HSt). In both cases, HSt serves as a kind of surfactant...

Poly(methyl methacrylate-ethyl acrylate-methacrylic acid) particles were synthesized by using a seeded soap-free emulsion polymerization process to obtain clean surfaces and surface carboxylic groups [115], Authors found that in this case dropwise addition process was better than batchswelling process to produce large particles with narrow size distribution. 

Soap-free emulsion polymerization (SFEP) is an ideal method for the preparation of surfactant-free polymer-LDH nanocomposites. The mechanism of SFEP involves an in situ micellization model, where the oligomeric radicals generated by the free radical reaction of an ionic initiator and styrene monomer act as surfactants and assist in forming micelles. Therefore, no surfactants are used during the emulsion polymerization process. The SFEP method has been applied to the preparation of a surfactant-free polystyrene-layered double hydroxide exfoliated nanocomposite.In a typical synthesis, 0.05 g of MgAlNOs was dispersed in 80 ml of distilled water and sonolyzed for 30 min. The mixture was charged into a 150 ml four-necked reactor equipped with a baffle stirrer, a reflux condenser, a nitrogen inlet and a septum. The temperature of the reactor was raised to 70 °C and then 5 g of styrene and 20 g of aqueous potassium persulfate (KPS) solution (0.4 wt%) were added to the reactor as... 

Figure 2.11 TEM images of PS MgAl-LDH samples with different polymerization times during soap-free emulsion polymerization (a) 0, (b) 60, (c) 180 and (d) 420 min. Reproduced with permission from reference 143.

PMMA-based Montmorillonite Nanocomposites by Soap-free Emulsion Polymerization... 

Figure 4.2 Schematic diagram of soap-free emulsion polymerization to fabricate PMMA latex particles.

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