Transition sphere-to-rod

Nevertheless, the rod-to-dumbbell-to-sphere transition seems to be a general crystal growth phenomenon and was observed for several other carbonate systems in the presence of DHBC additives (CaCOs, BaCOs, MnCOs, CdCOs) [61] as well as in rare cases even without additives. Thus it appears that the polymer additive does not only play a structme-directing role as the above discussion may imply, but also a controlling role for the release of building material consisting of amorphous particles. 

Angelico, R., Palazzo, G., Colafemmina, G., Cirkel, P. A., Giustini, M., and Ceglie, A. (1998), Water diffusion and head group mobility in polymer-like reverse micelle Evidence of a sphere-to-rod-sphere transition, J. Phys. Chem. B, 102, 2883-2889. 

Our results, based on UV-vis spectroscopy and TEM [62], indicate that spheroids (aspect ratio 2-5 with 12-30 nm short axis) are more reactive than spheres (20-30 nm) and nanorods (aspect ratio 18 with 16 nm short axis). In the presence of persulfate, spheroids convert to spheres (Figure 9.14), but similar size spheres and rods do not react at all, on the timescale of days. We presume that during the shape transition from spheroid to sphere, a fraction of gold atoms at the spheroid edges oxidize thus the particle diameter shrinks ( 5-10%) after persulfate treatment. 

Extensive studies have been reported by Kunieda s group regarding the formation of worm-like micelles and micellar transient networks in water-surfactant-cosurfactant systems. However, for applications, it is also relevant to know the effect of additives on systems containing worm-hke micelles. It is reported that oils induce a rod-sphere transition in surfactant micellar solutions, leading to a reduction in viscosity [32]. Kunieda s group studied the solubilization of different oils in wormlike micellar solutions [19, 33]. The amount of solubilized oil, its location within the micelle, and its effect on micellar shape and size demonstrated to strongly depend on the nature of the oil and its interactions with the surfactants. 

The possibility of entropy-driven phase separation in purely hard-core fluids has been of considerable recent interest experimentally, theoretically, and via computer simulations. Systems studied include binary mixtures of spheres (or colloids) of different diameters, mixtures of large colloidal spheres and flexible polymers, mixtures of colloidal spheres and rods," and a polymer/small molecule solvent mixture under infinite dilution conditions (here an athermal conformational coil-to-globule transition can occur)." For the latter three problems, PRISM theory could be applied, but to the best of our knowledge has not. The first problem is an old one solved analytically using PY integral equation theory by Lebowitz and Rowlinson." No liquid-liquid phase separation... 

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