PHYS01200704032 Debes Ray - Homi Bhabha National Institute

Chapter 2: Block Copolymer-mediated Synthesis of Gold Nanoparticles
Figure 2.5. Different structures of self-assembly of block copolymers: (a) spherical micelle,
(b) rod-like micelle, (c) vesicle and (d) lamellar.
Like surfactants, the micellization process for block copolymers is mainly governed
by two parameters, critical micellization temperature (CMT) and critical micellization
concentration (CMC). Self assembly will not occur if either of these is not reached and the
block copolymer will remain as unimers in the solution [123]. The CMC can be located by a
variety of techniques. The most commonly used being surface tensiometry where the CMC is
located as the point at which the surface tension becomes essentially independent of
concentration. On the other hand, if micelle formation is triggered, a thermodynamic
equilibrium will be reached between micelles and unimers. Several parameters have to be
considered to characterize a micellar system, such as the equilibrium constant, the quality of
the solvent, CMT, CMC, the overall mass molecular weight of the micelle, aggregation
number and morphology. These variables affect the hydrodynamic radius R H , the radius of
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