Microcapsules Made of Weak Polyelectrolytes:  Templating and Stimuli-Responsive Properties

Abstract

Hollow microcapsules composed of the weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) are templated on silicon oxide particles using the layer-by-layer adsorption. The colloidal template is removed with a buffer system of hydrofluoric acid and ammonium fluoride. With this buffer system, the template can be dissolved in mild pH conditions, where the polymeric layers are still stable. The morphology and the thickness of the resulting capsules are investigated with atomic force microscopy. The resulting hollow capsules show pH-dependent properties. The shells are stable over a broad pH range and swell and immediately dissolve for pH values below 2.3 and above 11. If the molecular weight of the poly(methacrylic acid) is increased, the enhanced entanglement of the polymers results in a reversible swelling of the capsules at low and at high pH. The swelling degree is probed with confocal laser scanning microscopy. In addition to the pH-dependent size variations, the different ionization degree of poly(methacrylic acid) as a function of pH is used for the selective binding of calcium ions.

Surface‐Engineered Nanocontainers for Entrapment of Corrosion Inhibitors

“…Increase of the permeability efficiency at alkaline pH, especially for nanocontainers with PAH/PSS shell is explained by the partial discharging of the PAH component of the multilayer system at increased pH followed by pore formation and even decomposition of the polyelectrolyte multilayers. [25] Nanocontainers constructed of strong PDADMAC/PSS polyelectrolyte shell are also less sensitive to the pH increase (Fig. 5B) as it was also observed in the acidic solution (Fig.…”

Polymer multilayer film formation studied by in situ ellipsometry and electrochemistry

“…In case of adjacent, flexible layers of poly(styrene sulfonate) (PSS) and poly (allylamine hydrochloride) (PAH) internal interface roughness measured by neutron reflectometry [21] and X-ray reflectivity [22] were found to be in the order of 2 nm. Amorphous nature of the polymer multilayers has been extensively studied also by scanning electron and atomic force microscopy [23], confocal spectroscopy [24], focused ion bean [25], surface plasma resonance [26], quartz crystal microbalance [27], ellipsometry [28], and electrochemistry [29].…”

Challenges and breakthroughs in recent research on self-assembly

“…Hollow capsules prepared by LbL techniques are appropriate objects for drug delivery [859,860]. Encapsulation and controlled delivery of DNA using LbL capsules have also been reported.…”