The role of Polymer–AuNP interaction in the stimuli-response properties of PPA–AuNP nanocomposites

Abstract

The helical sense control of dynamic helical polymers such as poly(phenylacetylene)s (PPAs) is greatly affected when they are conjugated to AuNPs through a strong thiol-Au connection, which restricts conformational changes at the polymer. Thus, the classical thiol-MNP bonds must be replaced by weaker ones, such as supramolecular amide–Au interactions. A straightforward preparation of the PPA–Au nanocomposite by reduction of a preformed PPA–Au3+ complex cannot be used due to a redox reaction between the two components of the complex which degrades the polymer. To avoid the interaction between the PPA and the Au3+ ions before the reduction takes place, the metal ions are added to the polymer solution capped as a TOAB complex, which keeps the PPA stable due to the lack of PPA–Au3+ interactions. Ulterior reduction of the Au3+ ions by NaBH4 affords the desired nanocomposite, where the AuNPs are stabilized by supramolecular anilide–AuNPs interactions. By using this approach, 3.7 nm gold nanoparticles are generated and aligned along the polymer chain with a regular distance between particles of 6 nm that corresponds to two helical pitches. These nanocomposites show stimuli-responsive properties and are also able to form macroscopically chiral nanospheres with tunable size