Nanostructures from Polymerized Surfactant Assemblies

Hexagonally packed monodisperse carboxylic acid-rich channels fixed by polymerization 

A particularly interesting study that exemplifies the effect of nano-confinement is one where poly(phenylene vinylene) PPV, a luminescent polymer, was incorporated into the channels formed from these polymerized hexagonal phases [78]. These hexagonal PPV nanocomposites exhibited a significant enhancement in the photoluminescence quantum yields, from ca. 25 to 80%. The origin of this enhancement is ascribed to the prevention of the formation of poorly emissive inter-chain excitonic species as a result of the confinement of the PPV chains into well-defined and well-separated nanochannels. An important feature of these nanocomposites was that they could be readily processed into thin films and fibres and, more importantly, macroscopic alignment of the channels encapsulating the PPV chains led to polarized emission [79]. 

The generation of nanoporous polymeric materials with controllable pore dimensions serves as an alternative to the inorganic counterparts, as in zeolites. The 

In the context of utilizing surfactant assemblies for building nanostructured polymeric materials, one other approach that deserves mention is the polymerization of standard monomers partitioned into the hydrophobic regions of surfactant aggregates one in particular that has received a lot of attention is vesicle templating [84]. The basic idea in this approach is to generate vesicles using appropriate surfactants and then to solubilize standard monomers, such as styrene, within the 

One of the hotly debated issues in the context of this approach is the retention of the original structure and the homogeneous distribution of the polymer chains 

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In the acidic route (with pH < 2), both kinetic and thermodynamic controlling factors need to be considered. First, the acid catalysis speeds up the hydrolysis of silicon alkoxides. Second, the silica species in solution are positively charged as =SiOH2 (denoted as I+). Finally, the siloxane bond condensation rate is kinetically promoted near the micelle surface. The surfactant (S+)-silica interaction in S+X 11 is mediated by the counterion X-. The micelle-counterion interaction is in thermodynamic equilibrium. Thus the factors involved in determining the total rate of nanostructure formation are the counterion adsorption equilibrium of X on the micellar surface, surface-enhanced concentration of I+, and proton-catalysed silica condensation near the micellar surface. From consideration of the surfactant, the surfactants first form micelles as a combination of the S+X assemblies, which then form a liquid crystal with molecular silicate species, and finally the mesoporous material is formed through inorganic polymerization and condensation of the silicate species. In the S+X I+ model, the surfactant-to-counteranion... 

In the framework of this research topic, PPy chains self-assembled in nanowires with a coral-like shape can be obtained by FeCb induced oxidative polymerization and dodecil-benzenic sulphonic acid (DBSA) dopant [106] oxidative polymerization is a widely used method for the attainment of polymeric nanostructures. For example, bundles of self-assembled PPy nanotubes have been fabricated by polymerization reaction with bis(2-ethylhexyl) sulfosuccinate reverse (water-in-oil) emulsions [107] and rods with enhanced electrical conductivity and thermal stability are reported to be formed via a self-assembly process of micelle obtained from a oxidative polymerization in the presence of p-toluensulfonic acid used as surfactant and doping agent [108, 109]. A further example of PPy nanotubes synthesized by oxidative polymerization in octane is reported in Fig. 1.7 [107]. 

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