Polymeric microemulsions

Desai S D, Gordon R D, Gronda A M and Cussler E L 1996 Polymerized microemulsions Curr. Opin. Colloid Interface Sc/. 1 519-22... 

In this context numerous changes were made. The chapter Properties of Polymers was revised and a new section Correlations of Structure and Morphology with the Properties of Polymers was added. The chapter Characterization of Macromolecules was revised and enlarged. 15 examples have been deleted as they did no longer represent the state of the art and/or were of minor educational value. Several new experiments (plus background text) were added, as, for example controlled radical polymerization - enzymatic polymerization - microemulsions - polyelectrolytes as superabsorbants - hyperbranched polymers - new blockcopolymers - high impact polystyrene - electrical conducting polymers. 

Several morphological studies of polymeric microemulsion have involved graft and block PSt/PEO copolymers in ternary solvent mixtures containing toluene, water, and either an alcohol or an amine acting as a cosurfactant [57,58]. The co-emulsifier increases the dispersion capacity of the copolymers. 

There are four main types of liquid-phase heterogeneous free-radical polymerization microemulsion polymerization, emulsion polymerization, miniemulsion polymerization and dispersion polymerization, all of which can produce nano- to micron-sized polymeric particles. Emulsion polymerization is sometimes called macroemulsion polymerization. In recent years, these heterophase polymerization reactions have become more and more important... 

Keywords Microemulsion polymerization Microemulsion reaction Water-in-Oil (W/O) microemulsion Oil-in-Water (0/W) microemulsion Bicontinuous microemulsion Functional membranes and inorganic/polymer nanocomposites... 

Fig. 8 SEM micrograph of the polymerized microemulsion solid, that contains the polymerizable non-ionic surfactant Ci-PEO-C,-MA-40 [96], after ethanol extraction...

This book on polymeric microemulsions is an attempt at a rapprochement of the methods and structures encountered in the two disciplines. The purpose of this book is to investigate polymer-polymer or polymer-surfactant interactions in solution leading to association structures with properties such as solubilization and anisotropy. These properties are useful in a wide variety of industries such as pharmaceutics, cosmetics, textiles, detergents, and paints. 

Preparation and Polymerization of (0/W) Cetyltrimethylammonium Bromide Microemulsion (CTAB-yE) (5-7). An oil in water pE composed of 1.0 g of CTAB, 0.5 g of hexanol, and 1.0 g of 50% styrene-divinylbenzene in 50 mL of water was carefully prepared by slowly adding the water to a stirred mixture of the other components to yield a slightly bluish clear solution. A 0.1% solution (w/w) of initiator AIBN (based on monomer) was then solubilized in the system followed by removal of 02 (by gentle N2 bubbling for 5 min), and finally the system was heated in an oil bath (50°C) until complete polymerization was achieved as determined spectrophotometrically. Proper dilution with water was then made to give a 0.01 M CTAB-P-pE solution P-pE indicates polymerized microemulsion. 

Polymerized Microemulsion Systems. A microemulsion of styrene and divinylbenzene with CTAB + hexanol may readily be made, and subsequently polymerized to form a polymerized microemulsion (5,6,7). This system exhibits two sites of solubilisation for photosystems such as pyrene, one in the surfactant skin layer, and the other in the polymerized styrene-divinylbenzene core. Photochemical reactions induced in the surfactant skin are very similar to those observed in micelles and are not immediately of concern to us at this stage. However, photochemical reactions induced in the rigid polymerized core are of interest, as they essentially confine reactants to a small region of space where movement is restricted as compared to a fluid non-polymerised microemulsion or a micelle. Thus, diffusion is minimised, and it may be possible to investigate reactions which occur over a distance rather than reactions which occur by diffusion. In order to eliminate reactions in the surfactant skin a microemulsion can be constructed which contains cetyl pyridinium chloride in place of CTAB. The pyrene that resides in the surfactant skin layer is immediately quenched by the pyridinium group following excitation. 

Figure 7.4 Freeze-fracture SEM micrograph mesoporous polymeric networks obtained by sulphur monochloride cross-linking of polyisoprene in bicontinuous polymeric microemulsions of polyisoprene and polystyrene. (From Ref. [9], reprinted with permission of the American Chemical Society.)...

After an efficient system has been found, the main open question is how to solidify the foams. One route could be to utilise water-soluble polymers or/and polymerise water-soluble monomers. Another route could be to switch to polymeric microemulsions. One would stepwisely replace the water by the preferred polymerisable hydrophilic monomer/polymer. By doing so one can be sure that the nanostructure of microemulsion remains unaffected. The generation of the nanofoam depends on the used monomer. A fixation via irradiation with fight would be preferable, when photoactive cross-linkers are... 

For blends containing diblock copolymers, interface enrichment by the copolymers as well as the potential reduction of the interfacial tension was investigated by Muller and Binder recently (Muller and Binder 2000). For weak segregation, the addition of copolymers led to compatibilization. At high incompatibilities, the homopolymer-rich phase could accommodate only a small fraction of the copolymer before the formation of a copolymer lamellar phase. The analysis of interfacial fluctuations yielded an estimate for the bending rigidity of the interface. The latter quantity is important for the formation of a polymeric microemulsion at intermediate segregation. 

Keywords Polymer blends Self-consistent field theory External potential dynamics Field-theoretic polymer simulations Polymeric microemulsion Polymer dynamics... 

Bulk or mass polymerization" Gas-phase pol3mierization Precipitation polymerization Suspension polymerization Microsuspension polymerization Dispersion polymerization Emulsion polymerization Miniemulsion polymerization Microemulsion polymerization... 

Desai, S. D., Polymerized Microemulsions, Curr. Opinion Colloid Interface Sci., 1, 519 (1996). 

M.E. Cates in Proc. ACS-Symp. on Polymeric Microemulsions and Polymer-Microemulsion Interaction, New Orleans, (1987)... 

Antonietti et al. [ 1 ] and Wu [2] have reported on the size control of the polymerized microemulsion in the system styrene, di-isopropenylbenzene (cross-linker), cetyltrimethylammo-niumchloride (CTMACI) or a similar surfactant, and water. According to a simple model developed by Wu [2] the resulting latex size is a function of the fleet ratio s = mjmyi with ms and /wm, the masses of surfactant and monomer respectively, given by... 

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