Periodic cooperative self-assembly

Figure 18.1 Synthesis of periodic mesoporous materiais assisted by SDAs (A). Route 1 true liquid crystal templating mechanism. Route 2 cooperative self-assembly mechanism. (Adapted from Refs [44,45].)...

NUCLEATION. The polymer self-assembly theory of Oosawa and KasaP treats nucleation as a highly cooperative and unfavorable event. Their kinetic theory for nucleation permits one to obtain information about the size of the polymerization nuclei, provided that two basic assumptions can be satisfied experimentally. First, the rate of nuclei formation is assumed to be proportional to the ioth power of the protomer concentration, with io representing the number of protomers required to create the nucleus. Second, the treatment deals only with that period during which the polymerization rate greatly exceeds the rate of protomer loss from the polymers (i.e., the initial stage of polymerization when the protomer concentration is the highest). 

The complex formation of PECs and PE-surfs is closely linked to self-assembly processes. A major difference between PECs and PE-surfs can be found in their solid-state structures. PE-surfs show typically highly ordered mesophases in the solid state [15] which is in contrast to the ladder and scrambled-egg structures of PECs [2]. Reasons for the high ordering of PE-surfs are i) cooperative binding phenomena of the surfactant molecules onto the polyelectrolyte chains [16-18] and ii) the amphiphilicity of the surfactant molecules. A further result of the cooperative zipper mechanism between a polyelectrolyte and oppositely charged surfactant molecules is a 1 1 stoichiometry. The amphiphilicity of surfactants favors a microphase separation in PE-surfs that results in periodic nanostructures with repeat units of 1 to 10 nm. By contrast, structures of PECs normally display no such periodic nanostructures. 

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