Stepwise Unfolding of Single‐Chain Nanoparticles by Chemically Triggered Gates

Abstract

The orthogonal, stepwise, and order-independent unfolding of single-chain nanoparticles (SCNPs) is introduced as a key step towards actively controlling the folding dynamics of SCNPs. The SCNPs are compacted by multiple hydrogen bonds and host-guest interactions. Well-defined diblock (AB) and tetrablock (ABCD) copolymers are equipped with orthogonal recognition motifs via modular ligation along the lateral chain. Initially, single-chain folding of the diblock copolymer was induced by the host-guest complexation of benzo-21-crown-7 (B21C7, host) and a secondary ammonium salt (AS, guest), representing an efficient avenue for single-chain collapse. Next, both orthogonal Hamilton wedge (HW) and cyanuric acid (CA) as well as B21C7-AS motifs were employed to generate SCNPs based on the ABCD polymer system. Subsequently, the stepwise dual-gated and order-independent unfolding of the SCNPs was investigated by the addition of external stimuli. The folding and unfolding were explored by 1D (1) H NMR spectroscopy, dynamic light scattering (DLS), and diffusion-ordered NMR spectroscopy (DOSY).

Using anion recognition to control the folding and unfolding of a single chain phosphorescent polymer

“…1 To date, many noncovalent interactions have been exploited as reversible intramolecular forces to control the folding/unfolding of SCPNs. 2 For instance, Meijer and coworkers developed a series of 2-uriedopyrimidinone (UPy) dimerization-based SCPNs. By controlling the hydrogen bonding sites in the UPy units, the ability of a single polymer chain to form SCPNs could be tuned.…”

“…By controlling the hydrogen bonding sites in the UPy units, the ability of a single polymer chain to form SCPNs could be tuned. 2a,b Metal coordination, with a primary focus on rhodium and copper, has been used to cross-link polymers to form SCNPs. 2c,d For example, Palmans and co-workers grafted polynorbornene with 3,3-bis(acylamino)-2,2-bipyridine substituted benzene-1,3,5-tricarboxamides (BiPy-BTAs).…”

“…2a,b Metal coordination, with a primary focus on rhodium and copper, has been used to cross-link polymers to form SCNPs. 2c,d For example, Palmans and co-workers grafted polynorbornene with 3,3-bis(acylamino)-2,2-bipyridine substituted benzene-1,3,5-tricarboxamides (BiPy-BTAs). Driven by presumed intramolecularly π–π interactions, these polymers were found to fold into fluorescent nanoparticles whose emissive features could be quenched by the addition of copper.…”

“…Driven by presumed intramolecularly π–π interactions, these polymers were found to fold into fluorescent nanoparticles whose emissive features could be quenched by the addition of copper. 2d Scherman et al functionalized polymers with methyl viologen and naphthyl groups and showed that the addition of cucurbit[n]urils produced ternary host–guest complexes and promoted the formation of SCNPs. 2e Barner-Kowollik and co-workers recently reported SCPNs formed from the self-assembly of an ABCD-type tetrablock copolymer driven by a combination of benzo-21-crown-7/secondary ammonium salt host–guest interactions and those involving the Hamilton wedge/cyanuric acid hydrogen-bonding motif.…”

“…2d Scherman et al functionalized polymers with methyl viologen and naphthyl groups and showed that the addition of cucurbit[n]urils produced ternary host–guest complexes and promoted the formation of SCNPs. 2e Barner-Kowollik and co-workers recently reported SCPNs formed from the self-assembly of an ABCD-type tetrablock copolymer driven by a combination of benzo-21-crown-7/secondary ammonium salt host–guest interactions and those involving the Hamilton wedge/cyanuric acid hydrogen-bonding motif. 2f However, to our knowledge, anion recognition has yet to be explored as a means of controlling SCNP formation.…”