Micellar environment micelles only

Besides polyanions such as SPS, anionic surfactants were able to provide the negative charges needed to template the formation of electrically conductive PANI. Indeed, micelles of sodium dodecylbenzensulfonate (SDBS) were used successfully as templates to induce the formation of linear and electrically conductive PANI [38]. On the other hand, cationic and non-ionic surfactants did not provide the negative charges and low pH environment needed for the synthesis of conducting PANI, as expected. Using a similar approach, dodecyl dipheny-loxide disulfonate (DODD) was used as a bifunctional template for the enzymatic synthesis of PANI [39]. UV-Vis and electrical conductivity studies showed that the electrically-conducting form of PANI was only obtained above the critical micellar concentration (CMC) of DODD. The bifunctional nature of the DODD provided... 

From surface tension studies of bola-surfactants, it is concluded that they exhibit wicket-like conformations at the gas-water interface [239,428,430,431], In micelles and liquid crystals however, a stretched conformation is preferred [436,437] this implies that surface tension data and interfacial tension data do no more describe the micellar interface with all the implications for solubilization (compare Sect. 3.4). In fact, some reports stress the extremely low solubilization capacity of bola-surfactants [431,432, 437,438], although others obtain capacities comparable to the ones of the monomers [430]. Also noteworthy, solubilized fluorescence probes indicate a more polar environment for the solubilizates than in micelles of the monomers [430-432], but micellar aggregation numbers of the bola-surfactants are comparable or only slightly lower [429,432, 438, 439]. In exceptional cases, very high aggregation numbers and the existence of an additional pre-CMC are observed [440]. 

However, it is not only from an architectural viewpoint that dendrimers can be contrasted to organized assemblies. but micellar stabilization and organization of species in uncharacteristic environments are also suggested. Thus, stmctural attributes of branched frameworks ean be employed for such applications as aqueous solubilization of inherently water-insoluble species as well as molecular ordering based on noneovalent interaetions, such as //-bonding and ionic associations. The advent and current status of several dendritic micelles are herein ehronicled. 

The data presented in Fig. 5.7 demonstrate the enormous increase in counterion quadrupole relaxation rate which accompanies micelle formation. Temperature dependence studies [319-321 324 326], as well as studies of the bromine isotope effect [303 319-321 324 326], show that the counterions exchange between different binding environments at a rapid rate compared to that of relaxation. To rationalize the concentration dependence of counterion quadrupole relaxation in micellar solutions it has been assumed that only two binding sites for the counterions have to be considered, i,e, the counterions are either free or attached to the micelles. It is further assumed that the ratio of counterions to surfactant ions in the micelles is independent of concentration and that the pseudo-phase separation model of micelle formation applies. This model [313] treats micelle formation analogously to a phase separation, with the c.m.c. corresponding to the saturation concentration of the molecule-disperse amphiphile. With these assumptions it may be shown [322] that for concentrations below the... 

The intra-micellar collision rate between probe and quencher depends not only on the size but also on the shape of the micelles, an effect that can also be investigated since depends on N as IW", where a = 1 for spherical micelles and larger for other geometries. However, a complication of interpreting kq in terms of micellar shape is that it depends not only on the aggregate size and shape but also on the micro-viscosity of the environment for probe and quencher. 

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