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Posted: Dec 11, 2014
Researchers develop novel chiral nanostructures from helical polymers and metal salts
(Nanowerk News) The prestigious journal Angewandte Chemie publishes in its last issue a work ("Nanospheres, Nanotubes, Toroids, and Gels with Controlled Macroscopic Chirality") by researchers of the Nanobiomol Group at CiQUS (University of Santiago de Compostela, Spain). It describes a novel protocol to obtain different types of nanostructures from a single helical polymer and certain metal salts. This work has been selected as front cover of the Journal. The helical polymers employed in the research are poly(phenylacetylene)s.
An outstanding characteristic of these macromolecules is that their helicity —i.e., helical sense— can be tuned by the action of diverse external stimuli such as temperature, polarity or metal ions. Consequently, these polymers act as sensors.
With their work, the researches of CIQUS have incorporated this family of polymers into the nanostructure field. So, different types of nanostructures (nanospheres, nanotubes, nanotoroids) have been obtained from a single helical polymer and diverse metal cations. The latter fix specific conformations, act as crosslinking agents and modulate the helical sense of the polymer (either right-handed or lef-handed). As a result, chiral nanostructures with different shapes are obtained. A number of organic and inorganic substances can be encapsulated in their interior.
This research has been carried out by Felix Freire (Ramón y Cajal researcher) and Sandra Arias (predoctoral researcher), members of the Research Group of Emilio Quiñoá and Ricardo Riguera, also co-authors of the work. The Nanobiomol group is pioneer on the synthesis of new chiral nanostructures following bottom-up approaches through chemical methods in solution.
NANOBIOMOL has published related results on this hot research field in prestigious scientific journals such as The Journal of the Chemical Society and Chemical Science (Royal Chemical Society). Those articles have also been highlighted as Front Covers on those journals. Currently, the Group keeps working in the generation of novel nanostructures. The cover of Angewandte Chemie is highly coveted and is recognised and associated worldwide with the highest quality research from the top researchers in the field.
The interaction of a highly dynamic poly(aryl acetylene) (poly-1) with Li+, Na+, and Ag+ leads to macroscopically chiral supramolecular nanospheres, nanotubes, toroids, and gels. With Ag+, nanospheres with M helicity and tunable sizes are generated, which complement those obtained from the same polymer with divalent cations. With Li+ or Na+, poly-1 yields chiral nanotubes, gels, or toroids with encapsulating properties and M helicity. Right-handed supramolecular structures can be obtained by using the enantiomeric polymer. The interaction of poly-1 with Na+ produces nanostructures whose helicity is highly dependent on the solvation state of the cation.
Therefore, structures with either of the two helicities can be prepared from the same polymer by manipulation of the cosolvent. Such chiral nanotubes, toroids, and gels have previously not been obtained from helical polymer–metal complexes. Chiral nanospheres made of poly(aryl acetylene) that were previously assembled with metal(II) species can now be obtained with metal(I) species.