Nanoassemblies with light‐responsive size and density from linear flexible polyelectrolytes

Abstract

This study presents electrostatically self‐assembled nanoparticles from linear flexible polyelectrolytes (poly(diallyldimethylammonium chloride or quarternized poly(4‐vinylpyridine)) and an ionic photo‐isomerizable azo dye (Acid Yellow 38) that can change their size upon UV‐light irradiation. Assemblies with narrow size distribution are stable in aqueous solution. For samples with under‐stoichiometric dye load, UV‐light exposure triggers a size decrease, e.g. from a hydrodynamic radius of Rh = 94 nm to Rh = 62 nm for an Ay38‐PDADMAC sample with a charge ratio of lcharge = 0.7. Size changes are caused by trans‐cis isomerization of the dye, accompanied by a change in hydrophilicity, binding enthalpy and entropy. Assemblies are characterized by static and dynamic light scattering, atomic force microscopy, UV–vis spectroscopy and isothermal titration calorimetry. Zeta potential measurements give insight into the electrostatic stabilization and size‐control of the ionic nano‐assemblies, revealing a master curve of effective surface charge density versus hydrodynamic radius. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys., 2013

Porphyrin-Polyelectrolyte Nanoassemblies: The Role of Charge and Building Block Architecture in Self-Assembly

“…In previous studies, we already investigated the interactions of polyelectrolytes and different azo dyes . These showed that the size of the aggregates is coded by ∆ G .…”

“…An increasing gain in the free energy Δ G leads to larger hydrodynamic radii R H . Differing results herein are more similar to the observations for trivalent azo dyes, for which also no master curve could be found …”

“…In previous studies, we already investigated the interactions of polyelectrolytes and different azo dyes. [82][83][84] These showed that the size of the aggregates is coded by ∆G. An increasing gain in the free energy ∆G leads to larger hydrodynamic radii R H .…”

“…Differing results herein are more similar to the observations for trivalent azo dyes, for which also no master curve could be found. [82,84] Thermodynamic studies of porphyrin and polyelectrolyte are quite rare in literature. da Costa et al investigated the thermodynamic stability of TPPS-poly(2-vinylpyridine) (PVP) assemblies in aqueous solution.…”

Metalloporphyrin–polyelectrolyte assemblies in aqueous solution: Influence of the metal center and the polyelectrolyte architecture

“…Structure formation can take place via electrostatic interaction with oppositely charged entities, such as ionic porphyrins. During the last years, electrostatic self‐assembly emerged to a powerful tool to create different kinds of supramolecular nanostructures with a variety of shapes . Other noncovalent forces like hydrogen bonding, amphiphilicity, metal coordination, or π–π‐stacking have been exploited for self‐assembly as well.…”