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

Abstract

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.

Dissymmetric Chiral Poly(diphenylacetylene)s: Secondary Structure Elucidation and Dynamic Luminescence

“…[83,84] The number average molar mass (M n ) and molar mass dispersity (M w /M n ) of poly-1 were 1.4 × 10 4 and 1.43 respectively, as determined by gel permeation chromatography (GPC) using THF as eluent and polystyrene narrow standards (PSS) as calibrants. Taking advantage of the active ester present as pendant group, poly-1 was effectively transformed into poly-(S)-2 by coupling with NH 2 -Ala-OMe under common peptide coupling conditions (Figure 1), as confirmed by 19 F NMR and IR studies that corroborated the disappearance of the signals corresponding to the pentafluorophenol moeity (see Supporting Information).…”

“…These studies are inspired by the structure/function relationships present in biomacromolecules such as peptides, proteins, DNA or polysaccharides. Among non‐natural helical scaffolds, dynamic helical polymers constitute a very interesting family due to the possibility of tuning their helical sense or elongation through external stimuli [19–23] . The use of non‐natural building blocks to synthetize these polymers allows the creation of smart materials with applications in different fields such as sensing, [24–31] asymmetric synthesis, [32–36] chiral recognition [37] and separation [38–41] .…”

“…Only a few examples related to chiral PDPAs [72–85] are found in the literature compared to the large amount of work that has been done with PPAs [12–33, 37–51, 94–97] . This is due to the difficulty of obtaining the former polymers in the laboratory by polymerization of the corresponding diphenylacetylene monomers (DPA).…”

“…Among nonnatural helical scaffolds, dynamic helical polymers constitute a very interesting family due to the possibility of tuning their helical sense or elongation through external stimuli. [19][20][21][22][23] The use of non-natural building blocks to synthetize these polymers allows the creation of smart materials with applications in different fields such as sensing, [24][25][26][27][28][29][30][31] asymmetric synthesis, [32][33][34][35][36] chiral recognition [37] and separation. [38][39][40][41] However, in molecular engineering it is mandatory to establish structure/function relationships for these materials, a fact that will allow to determine and, if possible, refine the structural features involved in the functionality of the material.…”

Facile Fabrication of Hierarchically Porous Boronic Acid Group-Functionalized Monoliths With Optical Activity for Recognizing Glucose With Different Conformation

“…Thus, they have exhibited great potential in many fields, such as molecular recognition, asymmetric catalysis, and chiral separation. Currently, most of the materials based on helical polymers are nanoparticles ( Zhao and Deng, 2016 ; Zhao et al, 2016 ; Núñez-Martínez et al, 2021 ) or microspheres, ( Zhou et al, 2010 ; Liu et al, 2012 ; Zhang et al, 2012 ; Liang et al, 2016 ) which are inconvenient for practical applications. Therefore, developing monolithic materials based on helical polymers is necessary.…”