Size Switchable Supramolecular Nanoparticle Based on Azobenzene Derivative within Anionic Pillar[5]arene

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Anionic pillar[5]arene (2C-WP5A) and azobenzene derivative (Azo-py-OMe, G) form host-guest inclusion complexes.
• Pillararene-based host-guest chemistry enables the creation of novel supramolecular structures.

Purpose of the Study:

• To construct and characterize a photo/thermal-switchable supramolecular nanoparticle assembly.
• To investigate the host-induced aggregating (HIA) phenomenon for nanoparticle formation.
• To demonstrate reversible size changes in nanoparticles triggered by external stimuli.

Main Methods:

• Host-guest inclusion complexation studied via 1H NMR titration, 2D ROESY, and isothermal titration microcalorimetry (ITC).
• Nanoparticle characterization using Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS).
• Photo/thermal-isomerization of the azobenzene derivative to induce size changes.

Main Results:

• A stable 1:1 host-guest complex with a high association constant (Ka = 2.60 × 10^4 M^-1) was formed.
• Supramolecular nanoparticles were successfully synthesized via host-induced aggregation (HIA).
• Nanoparticle size reversibly switched from ~800 nm to ~250 nm upon photo/thermal isomerization, altering solution turbidity.

Conclusions:

• Photo/thermal-switchable supramolecular nanoparticles were successfully constructed.
• The host-induced aggregation method provides a facile route to nanoparticle assembly.
• Reversible size modulation of nanoparticles offers potential for smart material applications.