Dynamic Chiral PPA–AgNP Nanocomposites: Aligned Silver Nanoparticles Decorating Helical Polymers

A novel approach to prepare stimulus-sensitive nanocomposites is described, based on a dynamic helical polymer, chiral poly(phenylacetylene) (PPA), and silver nanoparticles. To preserve the dynamic helical behavior of PPA within the nanocomposite, a weak and adaptive supramolecular interaction, such as that between amide group–silver nanoparticle, is used to link the metal nanoparticle to the polymer. To prepare the composite, we chose PPA as a helical polymer that bears an amide group as a monomer repeating unit, poly-(R)-1, which can coordinate with Ag+ ions. The silver ions that form complexes with the pendant groups are further reduced, through the use of NaBH4, to AgNPs that are stabilized by the amide groups of PPA. As a result, 2.8 nm silver nanoparticles are formed and aligned along the polymer chain with a regular 3.1 nm interparticle distance corresponding to the helical pitch of the polymer. The weak amide/AgNP interactions allow PPA to adopt either P or M helical structures on the AgNPs through supramolecular adaptive mechanisms induced by appropriate external stimuli