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  • Author: Theo G.M. van de Ven x
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Linear alternating copolymers with one phenyl group per repeat unit self-assemble by π-π stacking, provided the phenyl groups are favorably orientated. Two molecules can zip together, with the phenyl groups acting as the teeth (or elements) of the zipper. An example of a macromolecule that can act as a molecular zipper is poly(styrene alt. maleic anhydride), referred to as SMA. In water, the maleic anhydride group is hydrolyzed, resulting in maleic acid that contains two carboxyl groups. When two SMA molecules are zipped together, only a fraction of the phenyl groups is engaged in the zipper, while others are free and available for further π-π stacking. This leads to additional self-assembly into sheets of SMA, consisting of parallel SMA molecules, all zipped together side by side. These sheets roll up to minimize their energy, forming hollow nanotubes. We review the experimental evidence for SMA nanotube formation and summarize the quantum mechanical calculations that predict their formation. The results of SMA are compared to those of SMI, a styrene-maleimide copolymer, formed by reacting SMA with 3-(dimethylamino)-1-propylamide. Since SMA is an alternating copolymer, SMI is an alternating copolymer as well. For certain alternating copolymers, the chirality of the copolymer is extremely important. This led to the investigation of alternating copolymers made from natural molecules, such as oligopeptides and oligosaccharides, which have an inherent chirality. Finally we discuss how these nanotubes can act as templates to make advanced materials.