Middle-phase microemulsions micrograph

Electron micrograph of inhibitor free styrene polymerized in a middle phase microemulsion system contsuning SDS and 2-i>entanol (x2000). 

Figure 5(e) Electron micrographs of inhibited styrene polymerized in a middle phase microemulsion containing SDS and 2-pentanol (xlOOO). Reproduced with permission from Ref. 24, Figure 1. Copyright 1988 John Wiley Sons.

Preliminary conductivity measurements indicate that the polymers based on the anionic system are ionically conductive, whereas the nonionic based polymers are non-conductive. AC impedance tests were done on a thick film ( limn thick) using sodium sulfate as the electrolyte in a specially designed closed cell. The resistivity of polystyrene obtained from middle phase microemulsions was found to be in the rjange of lOMO ohm-cm, compared to lO o -10 2 ohm-cm for bulk polystyrene. A thin film of the polymer was also obtained on graphite electrodes by UV irradiation. Electrochemicd measurements using such polymer coated electrodes also suggest that the film is conductive. SEM micrographs before and after the electrochemical measurements indicate that the polymeric film is stable and porous. 

Using various physicochemical techniques such as high resolution NMR, viscosity, and electrical resistivity measurements, Chan and Shah [26] proposed that the middle-phase microemulsion in three-phase systems at or near optimal salinity is a water-external microemulsion of spherical droplets of oil. Extended studies to characterize the middle-phase microemulsions by several techniques including freeze-fracture electron microscopy revealed the structure to be a water-external microemulsion [26]. The droplet size in the middle-phase microemulsion decreases with increasing salinity. A freeze-fracture electron micrograph of a middle-phase microemulsion is shown in Fig. 8. It clearly indicates that the discrete spherical structure of the oil droplets in a continuous aqueous phase is consistent with the mechanism proposed in Fig. 7. This system was extensively studied by Reed and coworkers [20-22]. 

Figure 8 Freeze-fracture scanning electron micrograph of a middle-phase microemulsion. The spherical shapes are oil droplets suspended within the continuous aqueous phase. (The black bar represents 0.5 m.)...

Fig. 3.14 Electron micrograph of styrene polymerized in middle-phase microemulsion containing anionic surfactant SDS (from [71], With permission from John Wiley Sons, Inc.)...

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