PS-b-PDMAEMA

Figure 6.22 Chemical structures of p) PS-b-PDMAEMA and pi) PSS used in the preparation of SWCNT dispersions.

Figure 6.23 Schematic of the final dispersion after the synthesis of AuNPs physi-sorbed onto PS-b-PDMAEMA-covered SWCNTs.

Figure 6.24 Exfoliation profile for 0.1 wt% SWCNT dispersions prepared in a 0.2 wt% SDS solution (squares), 0.4 wt% PSS (El, stars) and 0.4 wt% PS-b-PDMAEMA solutions (E2, circles).

For the block copolymer it is suspected that these micelles (polymer aggregates) will readily form in solution. Amphiphilic block copolymers are known to self-assemble into macromolecular micelles at very low concentrations. The presence ofthese polymer aggregates was confirmed by cryo-TEM. A cryo-TEM micrograph of a solution of a PS-b-PDMAEMA block (i) and a conventional TEM micrograph of the final dispersion obtained from an exfoliation performed using PS-b-PDMAEMA (ii) are shown in Figure 6.25. 

Figure 6.25 Micrographs from (i) cryoTEM imaging of a solution of a PS-b-PDMAEMA block and (ii) TEM imaging of an exfoliation prepared using PS-b-PDMAEMA.

Composites prepared with a PS-b-PDMAEMA/AuNP/SWCNT dispersion [AuNP Series 4) are examined and the final percolation thresholds are given in Figure 6.28, along with the control system where only SWCNTs are present. 

Staying in the framework of multicompartment micelles, one should note that the formation of this nanostructure can be also achieved by a mixture of two block copolymers. Zhang and coworkers have described the case of a thermoresponsive multicompartment micelle composed of two block copolymers, namely poly[N-(4-vinylbenzyl)-N,N-diethylamine)]-b-polystyrene (PVEA-b-PS) and poly[2-(dimethylamino) ethyl methacrylate]-b-polystyrene (PDMAEMA-b-PS) [22], A mixture of these copolymers, in a polar solvent, forms micelles where the PS core is decorated with PVEA nodules (Fig. 2.7). Depending on the solvent, the multicompartment nanostmcture can be either precipitated at elevated temperature, when water is used as solvent, or to be reformed into a regular micelle with PS core and mixed PVEA/PDMAEMA corona, when the solvent is methanol, just as it was described in the case of the pH-responsive terpolymer [19]. 

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